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{{About|evolution in biology|related articles|Outline of evolution|other uses}}{{pp-semi-protected|small=yes}}{{short description|change in the heritable characteristics of biological populations over successive generations}}{{See introduction}}{{Evolutionary biology}}{{Use British English|date=January 2014}}Evolution is change in the heritable characteristics of biological populations over successive generations.{{harvnb|Hall|Hallgrímsson|2008|pp=4–6}}WEB, Evolution Resources, Washington, DC, National Academies of Sciences, Engineering, and Medicine, 2016,weblink live,weblink" title="">weblink 2016-06-03, These characteristics are the expressions of genes that are passed on from parent to offspring during reproduction. Different characteristics tend to exist within any given population as a result of mutation, genetic recombination and other sources of genetic variation.{{harvnb|Futuyma|Kirkpatrick|2017|pp=79–102|loc=Chapter 4: Mutation and Variation}} Evolution occurs when evolutionary processes such as natural selection (including sexual selection) and genetic drift act on this variation, resulting in certain characteristics becoming more common or rare within a population.JOURNAL, Scott-Phillips, Thomas C., Laland, Kevin N., Shuker, David M., Dickins, Thomas E., West, Stuart A., Stuart West, May 2014, The Niche Construction Perspective: A Critical Appraisal, Evolution (journal), Evolution, 68, 5, 1231–1243, 10.1111/evo.12332, 0014-3820, 24325256, 4261998, live, Evolutionary processes are generally thought of as processes by which these changes occur. Four such processes are widely recognized: natural selection (in the broad sense, to include sexual selection), genetic drift, mutation, and migration (Fisher 1930; Haldane 1932). The latter two generate variation; the first two sort it., It is this process of evolution that has given rise to biodiversity at every level of biological organisation, including the levels of species, individual organisms and molecules.{{harvnb|Hall|Hallgrímsson|2008|pp=3–5}}{{harvnb|Voet|Voet|Pratt|2016|pp=1–22|loc=Chapter 1: Introduction to the Chemistry of Life}}The scientific theory of evolution by natural selection was conceived independently by Charles Darwin and Alfred Russel Wallace in the mid-19th century and was set out in detail in Darwin's book On the Origin of Species (1859).{{harvnb|Darwin|1859}} Evolution by natural selection was first demonstrated by the observation that more offspring are often produced than can possibly survive. This is followed by three observable facts about living organisms: (1) traits vary among individuals with respect to their morphology, physiology and behaviour (phenotypic variation), (2) different traits confer different rates of survival and reproduction (differential fitness) and (3) traits can be passed from generation to generation (heritability of fitness).JOURNAL, Lewontin, Richard C., Richard Lewontin, November 1970, The Units of Selection,weblink Annual Review of Ecology, Evolution, and Systematics, Annual Review of Ecology and Systematics, 1, 1–18, 10.1146/, 2096764, 1545-2069, live,weblink" title="">weblink 2015-02-06, Thus, in successive generations members of a population are more likely to be replaced by the progenies of parents with favourable characteristics that have enabled them to survive and reproduce in their respective environments. In the early 20th century, other competing ideas of evolution such as mutationism and orthogenesis were refuted as the modern synthesis reconciled Darwinian evolution with classical genetics, which established adaptive evolution as being caused by natural selection acting on Mendelian genetic variation.{{harvnb|Futuyma|Kirkpatrick|2017|pp=3–26|loc=Chapter 1: Evolutionary Biology}} All life on Earth shares a last universal common ancestor (LUCA){{harvnb|Kampourakis|2014|pp=127–129}}JOURNAL, Doolittle, W. Ford, Ford Doolittle, February 2000, Uprooting the Tree of Life,weblink Scientific American, 0036-8733, 282, 2, 90–95, 10.1038/scientificamerican0200-90, 10710791,weblink" title="">weblink 2006-09-07, 2015-04-05, 2000SciAm.282b..90D, JOURNAL, Glansdorff, Nicolas, Ying Xu, Labedan, Bernard, July 9, 2008, The Last Universal Common Ancestor: emergence, constitution and genetic legacy of an elusive forerunner, Biology Direct, 3, 29, 10.1186/1745-6150-3-29, 1745-6150, 2478661, 18613974, that lived approximately 3.5–3.8 billion years ago. The fossil record includes a progression from early biogenic graphite, to microbial mat fossils, to fossilised multicellular organisms. Existing patterns of biodiversity have been shaped by repeated formations of new species (speciation), changes within species (anagenesis) and loss of species (extinction) throughout the evolutionary history of life on Earth.{{harvnb|Futuyma|2004|p=33}} Morphological and biochemical traits are more similar among species that share a more recent common ancestor, and can be used to reconstruct phylogenetic trees.{{harvnb|Panno|2005|pp=xv-16}}NAS 2008, p. 17 {{webarchive|url= |date=2015-06-30}}Evolutionary biologists have continued to study various aspects of evolution by forming and testing hypotheses as well as constructing theories based on evidence from the field or laboratory and on data generated by the methods of mathematical and theoretical biology. Their discoveries have influenced not just the development of biology but numerous other scientific and industrial fields, including agriculture, medicine and computer science.WEB,weblink Evolution, Science, and Society: Evolutionary Biology and the National Research Agenda, 1999, Futuyma, Douglas J., Douglas J. Futuyma, Office of University Publications, Rutgers University, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, Executive summary, 43422991,weblink" title="">weblink 2012-01-31, 2014-11-24,

History of evolutionary thought

File:Lucretius Rome.jpg|thumb|upright|LucretiusLucretiusFile:Alfred-Russel-Wallace-c1895.jpg|thumb|upright|Alfred Russel WallaceAlfred Russel WallaceFile:Thomas Robert Malthus Wellcome L0069037 -crop.jpg|thumb|upright|Thomas Robert MalthusThomas Robert MalthusFile:Charles Darwin aged 51.jpg|thumb|upright|In 1842, Charles Darwin penned his first sketch of Darwin|1909|p=53}}{{further|History of speciation}}

Classical times

The proposal that one type of organism could descend from another type goes back to some of the first pre-Socratic Greek philosophers, such as Anaximander and Empedocles.{{harvnb|Kirk|Raven|Schofield|1983|pp=100–142, 280–321}} Such proposals survived into Roman times. The poet and philosopher Lucretius followed Empedocles in his masterwork De rerum natura (On the Nature of Things).{{harvnb|Lucretius}}JOURNAL, Sedley, David, David Sedley, 2003, Lucretius and the New Empedocles,weblink Leeds International Classical Studies, 2, 4, 1477-3643, 2014-11-25, dead,weblink" title="">weblink 2014-08-23,


In contrast to these materialistic views, Aristotelianism considered all natural things as actualisations of fixed natural possibilities, known as forms.JOURNAL, Torrey, Harry Beal, Felin, Frances, March 1937, Was Aristotle an Evolutionist?, The Quarterly Review of Biology, 12, 1, 1–18, 10.1086/394520, 0033-5770, 2808399, JOURNAL, Hull, David L., David Hull, December 1967, The Metaphysics of Evolution, The British Journal for the History of Science, Cambridge, Cambridge University Press on behalf of British Society for the History of Science, The British Society for the History of Science, 3, 4, 309–337, 10.1017/S0007087400002892, 4024958, This was part of a medieval teleological understanding of nature in which all things have an intended role to play in a divine cosmic order. Variations of this idea became the standard understanding of the Middle Ages and were integrated into Christian learning, but Aristotle did not demand that real types of organisms always correspond one-for-one with exact metaphysical forms and specifically gave examples of how new types of living things could come to be.{{harvnb|Mason|1962|pp=43–44}}


In the 17th century, the new method of modern science rejected the Aristotelian approach. It sought explanations of natural phenomena in terms of physical laws that were the same for all visible things and that did not require the existence of any fixed natural categories or divine cosmic order. However, this new approach was slow to take root in the biological sciences, the last bastion of the concept of fixed natural types. John Ray applied one of the previously more general terms for fixed natural types, "species", to plant and animal types, but he strictly identified each type of living thing as a species and proposed that each species could be defined by the features that perpetuated themselves generation after generation.{{harvnb|Mayr|1982|pp=256–257}}
  • {{harvnb|Ray|1686}} The biological classification introduced by Carl Linnaeus in 1735 explicitly recognised the hierarchical nature of species relationships, but still viewed species as fixed according to a divine plan.WEB,weblink Carl Linnaeus (1707-1778), Waggoner, Ben, July 7, 2000, Evolution, University of California Museum of Paleontology, Berkeley, California, Online exhibit, 2012-02-11, live,weblink" title="">weblink 2011-04-30,
Other naturalists of this time speculated on the evolutionary change of species over time according to natural laws. In 1751, Pierre Louis Maupertuis wrote of natural modifications occurring during reproduction and accumulating over many generations to produce new species.{{harvnb|Bowler|2003|pp=73–75}} Georges-Louis Leclerc, Comte de Buffon suggested that species could degenerate into different organisms, and Erasmus Darwin proposed that all warm-blooded animals could have descended from a single microorganism (or "filament").WEB,weblink Erasmus Darwin (1731-1802), October 4, 1995, Evolution, University of California Museum of Paleontology, Berkeley, California, Online exhibit, 2012-02-11, live,weblink" title="">weblink 2012-01-19, The first full-fledged evolutionary scheme was Jean-Baptiste Lamarck's "transmutation" theory of 1809,{{harvnb|Lamarck|1809}} which envisaged spontaneous generation continually producing simple forms of life that developed greater complexity in parallel lineages with an inherent progressive tendency, and postulated that on a local level, these lineages adapted to the environment by inheriting changes caused by their use or disuse in parents.{{harvnb|Nardon|Grenier|1991|p=162}}{{harvnb|Gould|2002}}{{page needed|date=December 2013}} (The latter process was later called Lamarckism.)JOURNAL, Ghiselin, Michael T., Michael Ghiselin, September–October 1994, The Imaginary Lamarck: A Look at Bogus 'History' in Schoolbooks,weblink The Textbook Letter, 23228649, 2008-01-23, dead,weblink" title="">weblink 2008-02-12, {{harvnb|Magner|2002}}{{page needed|date=December 2013}}JOURNAL, Jablonka, Eva, Eva Jablonka, Lamb, Marion J., Marion J. Lamb, August 2007, Précis of Evolution in Four Dimensions, Behavioral and Brain Sciences, 30, 4, 353–365, 10.1017/S0140525X07002221, 18081952, 0140-525X, These ideas were condemned by established naturalists as speculation lacking empirical support. In particular, Georges Cuvier insisted that species were unrelated and fixed, their similarities reflecting divine design for functional needs. In the meantime, Ray's ideas of benevolent design had been developed by William Paley into the Natural Theology or Evidences of the Existence and Attributes of the Deity (1802), which proposed complex adaptations as evidence of divine design and which was admired by Charles Darwin.{{harvnb|Burkhardt|Smith|1991}}

Darwinian revolution

The crucial break from the concept of constant typological classes or types in biology came with the theory of evolution through natural selection, which was formulated by Charles Darwin in terms of variable populations. Darwin used the expression "descent with modification" rather than "evolution".WEB,weblink Search results for "descent with modification" - The Complete Work of Charles Darwin Online, Partly influenced by An Essay on the Principle of Population (1798) by Thomas Robert Malthus, Darwin noted that population growth would lead to a "struggle for existence" in which favourable variations prevailed as others perished. In each generation, many offspring fail to survive to an age of reproduction because of limited resources. This could explain the diversity of plants and animals from a common ancestry through the working of natural laws in the same way for all types of organism.JOURNAL, Sober, Elliott, Elliott Sober, June 16, 2009, Did Darwin write the Origin backwards?, Proceedings of the National Academy of Sciences of the United States of America, Proc. Natl. Acad. Sci. U.S.A., 106, Suppl. 1, 10048–10055, 2009PNAS..10610048S, 10.1073/pnas.0901109106, 0027-8424, 19528655, 2702806, {{harvnb|Mayr|2002|p=165}}{{harvnb|Bowler|2003|pp=145–146}}JOURNAL, Sokal, Robert R., Robert R. Sokal, Crovello, Theodore J., March–April 1970, The Biological Species Concept: A Critical Evaluation, The American Naturalist, 104, 936, 127–153, 10.1086/282646, 0003-0147, 2459191, Darwin developed his theory of "natural selection" from 1838 onwards and was writing up his "big book" on the subject when Alfred Russel Wallace sent him a version of virtually the same theory in 1858. Their separate papers were presented together at an 1858 meeting of the Linnean Society of London.JOURNAL, Darwin, Charles, Charles Darwin, Wallace, Alfred, Alfred Russel Wallace, August 20, 1858, On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection,weblink Zoological Journal of the Linnean Society, Journal of the Proceedings of the Linnean Society of London. Zoology, 3, 9, 45–62, 10.1111/j.1096-3642.1858.tb02500.x, 1096-3642, 2007-05-13, live,weblink" title="">weblink 2007-07-14, At the end of 1859, Darwin's publication of his "abstract" as On the Origin of Species explained natural selection in detail and in a way that led to an increasingly wide acceptance of Darwin's concepts of evolution at the expense of alternative theories. Thomas Henry Huxley applied Darwin's ideas to humans, using paleontology and comparative anatomy to provide strong evidence that humans and apes shared a common ancestry. Some were disturbed by this since it implied that humans did not have a special place in the universe.ENCYCLOPEDIA, Desmond, Adrian J., Adrian Desmond, Encyclopædia Britannica Online,weblink Thomas Henry Huxley, 2014-12-02, July 17, 2014, Encyclopædia Britannica, Inc., Chicago, Illinois, live,weblink" title="">weblink January 19, 2015,

Pangenesis and heredity

The mechanisms of reproductive heritability and the origin of new traits remained a mystery. Towards this end, Darwin developed his provisional theory of pangenesis.JOURNAL, Y. -S. Liu, X. M. Zhou, M. X. Zhi, X. J. Li, Q. L. Wang, September 2009, Darwin's contributions to genetics, Journal of Applied Genetics, 50, 3, 177–184, 10.1007/BF03195671, 1234-1983, 19638672, In 1865, Gregor Mendel reported that traits were inherited in a predictable manner through the independent assortment and segregation of elements (later known as genes). Mendel's laws of inheritance eventually supplanted most of Darwin's pangenesis theory.JOURNAL, Weiling, Franz, July 1991, Historical study: Johann Gregor Mendel 1822–1884, American Journal of Medical Genetics, 40, 1, 1–25; discussion 26, 10.1002/ajmg.1320400103, 1887835, August Weismann made the important distinction between germ cells that give rise to gametes (such as sperm and egg cells) and the somatic cells of the body, demonstrating that heredity passes through the germ line only. Hugo de Vries connected Darwin's pangenesis theory to Weismann's germ/soma cell distinction and proposed that Darwin's pangenes were concentrated in the cell nucleus and when expressed they could move into the cytoplasm to change the cell's structure. De Vries was also one of the researchers who made Mendel's work well known, believing that Mendelian traits corresponded to the transfer of heritable variations along the germline.{{harvnb|Wright|1984|p=480}} To explain how new variants originate, de Vries developed a mutation theory that led to a temporary rift between those who accepted Darwinian evolution and biometricians who allied with de Vries.{{harvnb|Provine|1971}}JOURNAL, Stamhuis, Ida H., Meijer, Onno G., Zevenhuizen, Erik J. A., June 1999, Hugo de Vries on Heredity, 1889-1903: Statistics, Mendelian Laws, Pangenes, Mutations, 90, 2, 238–267, Isis (journal), Isis, 10.1086/384323, 237050, 10439561, In the 1930s, pioneers in the field of population genetics, such as Ronald Fisher, Sewall Wright and J. B. S. Haldane set the foundations of evolution onto a robust statistical philosophy. The false contradiction between Darwin's theory, genetic mutations, and Mendelian inheritance was thus reconciled.{{harvnb|Quammen|2006}}{{page needed|date=December 2014}}

The 'modern synthesis'

In the 1920s and 1930s the so-called modern synthesis connected natural selection and population genetics, based on Mendelian inheritance, into a unified theory that applied generally to any branch of biology. The modern synthesis explained patterns observed across species in populations, through fossil transitions in palaeontology, and complex cellular mechanisms in developmental biology.{{harvnb|Bowler|1989}}{{page needed|date=December 2013}} The publication of the structure of DNA by James Watson and Francis Crick with contribution of Rosalind Franklin in 1953 demonstrated a physical mechanism for inheritance.JOURNAL, Watson, J. D., James Watson, Crick, F. H. C., Francis Crick, April 25, 1953, Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid,weblink Nature (journal), Nature, 171, 4356, 737–738, 1953Natur.171..737W, 10.1038/171737a0, 0028-0836, 13054692, 2014-12-04, It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material., live,weblink" title="">weblink 2014-08-23, Molecular biology improved understanding of the relationship between genotype and phenotype. Advancements were also made in phylogenetic systematics, mapping the transition of traits into a comparative and testable framework through the publication and use of evolutionary trees.{{harvnb|Hennig|1999|p=280}}{{harvnb|Wiley|Lieberman|2011}}{{page needed|date=December 2013}} In 1973, evolutionary biologist Theodosius Dobzhansky penned that "nothing in biology makes sense except in the light of evolution," because it has brought to light the relations of what first seemed disjointed facts in natural history into a coherent explanatory body of knowledge that describes and predicts many observable facts about life on this planet.JOURNAL, Dobzhansky, Theodosius, Theodosius Dobzhansky, March 1973, Nothing in Biology Makes Sense Except in the Light of Evolution,weblink The American Biology Teacher, 35, 3, 125–129, 10.2307/4444260, live,weblink" title="">weblink 2015-10-23, 4444260,,

Further syntheses

Since then, the modern synthesis has been further extended to explain biological phenomena across the full and integrative scale of the biological hierarchy, from genes to species. One extension, known as evolutionary developmental biology and informally called "evo-devo," emphasises how changes between generations (evolution) acts on patterns of change within individual organisms (development).JOURNAL, Kutschera, Ulrich, Ulrich Kutschera, Niklas, Karl J., Karl J. Niklas, June 2004, The modern theory of biological evolution: an expanded synthesis, Naturwissenschaften, 91, 6, 255–276, 2004NW.....91..255K, 10.1007/s00114-004-0515-y, 1432-1904, 15241603, {{harvnb|Cracraft|Bybee|2005}}{{page needed|date=December 2014}}JOURNAL, Avise, John C., John Avise, Ayala, Francisco J., Francisco J. Ayala, May 11, 2010, In the light of evolution IV: The human condition,weblink Proc. Natl. Acad. Sci. U.S.A., 107, Suppl. 2, 8897–8901, 10.1073/pnas.1003214107, 20460311, 3024015, 0027-8424, 2014-12-29, live,weblink" title="">weblink 2014-08-23, Since the beginning of the 21st century and in light of discoveries made in recent decades, some biologists have argued for an extended evolutionary synthesis, which would account for the effects of non-genetic inheritance modes, such as epigenetics, parental effects, ecological inheritance and cultural inheritance, and evolvability.JOURNAL, Danchin, Étienne, Charmantier, Anne, Champagne, Frances A., Frances Champagne, Mesoudi, Alex, Pujol, Benoit, Blanchet, Simon, June 2011, Beyond DNA: integrating inclusive inheritance into an extended theory of evolution, Nature Reviews Genetics, 12, 7, 475–486, 10.1038/nrg3028, 1471-0056, 21681209, {{harvnb|Pigliucci|Müller|2010}}


{{Further|Introduction to genetics|Genetics|Heredity|Reaction norm}}File:ADN static.png|thumb|upright|DNA structure. Bases are in the centre, surrounded by phosphate–sugar chains in a double helix.]]Evolution in organisms occurs through changes in heritable traits—the inherited characteristics of an organism. In humans, for example, eye colour is an inherited characteristic and an individual might inherit the "brown-eye trait" from one of their parents.JOURNAL, Sturm, Richard A., Frudakis, Tony N., August 2004, Eye colour: portals into pigmentation genes and ancestry, Trends (journals), Trends in Genetics, 20, 8, 327–332, 10.1016/j.tig.2004.06.010, 0168-9525, 15262401, Inherited traits are controlled by genes and the complete set of genes within an organism's genome (genetic material) is called its genotype.JOURNAL, Pearson, Helen, May 25, 2006, Genetics: What is a gene?, Nature, 441, 7092, 398–401, 2006Natur.441..398P, 10.1038/441398a, 0028-0836, 16724031, The complete set of observable traits that make up the structure and behaviour of an organism is called its phenotype. These traits come from the interaction of its genotype with the environment.JOURNAL, Visscher, Peter M., Hill, William G., William G. Hill, Wray, Naomi R., Naomi Wray, April 2008, Heritability in the genomics era — concepts and misconceptions, Nature Reviews Genetics, 9, 4, 255–266, 10.1038/nrg2322, 1471-0056, 18319743, As a result, many aspects of an organism's phenotype are not inherited. For example, suntanned skin comes from the interaction between a person's genotype and sunlight; thus, suntans are not passed on to people's children. However, some people tan more easily than others, due to differences in genotypic variation; a striking example are people with the inherited trait of albinism, who do not tan at all and are very sensitive to sunburn.JOURNAL, Oetting, William S., Brilliant, Murray H., King, Richard A., August 1996, The clinical spectrum of albinism in humans, Trends (journals), Molecular Medicine Today, 2, 8, 330–335, 10.1016/1357-4310(96)81798-9, 1357-4310, 8796918, Heritable traits are passed from one generation to the next via DNA, a molecule that encodes genetic information. DNA is a long biopolymer composed of four types of bases. The sequence of bases along a particular DNA molecule specify the genetic information, in a manner similar to a sequence of letters spelling out a sentence. Before a cell divides, the DNA is copied, so that each of the resulting two cells will inherit the DNA sequence. Portions of a DNA molecule that specify a single functional unit are called genes; different genes have different sequences of bases. Within cells, the long strands of DNA form condensed structures called chromosomes. The specific location of a DNA sequence within a chromosome is known as a locus. If the DNA sequence at a locus varies between individuals, the different forms of this sequence are called alleles. DNA sequences can change through mutations, producing new alleles. If a mutation occurs within a gene, the new allele may affect the trait that the gene controls, altering the phenotype of the organism.{{harvnb|Futuyma|2005}}{{page needed|date=December 2014}} However, while this simple correspondence between an allele and a trait works in some cases, most traits are more complex and are controlled by quantitative trait loci (multiple interacting genes).JOURNAL, Phillips, Patrick C., November 2008, Epistasis—the essential role of gene interactions in the structure and evolution of genetic systems, Nature Reviews Genetics, 9, 11, 855–867, 10.1038/nrg2452, 1471-0056, 2689140, 18852697, JOURNAL, Rongling Wu, Min Lin, March 2006, Functional mapping — how to map and study the genetic architecture of dynamic complex traits, Nature Reviews Genetics, 7, 3, 229–237, 10.1038/nrg1804, 1471-0056, 16485021, Recent findings have confirmed important examples of heritable changes that cannot be explained by changes to the sequence of nucleotides in the DNA. These phenomena are classed as epigenetic inheritance systems.JOURNAL, Jablonka, Eva, Raz, Gal, June 2009, Transgenerational Epigenetic Inheritance: Prevalence, Mechanisms, and Implications for the Study of Heredity and Evolution, The Quarterly Review of Biology, 84, 2, 131–176, 10.1086/598822, 0033-5770, 19606595,weblink, DNA methylation marking chromatin, self-sustaining metabolic loops, gene silencing by RNA interference and the three-dimensional conformation of proteins (such as prions) are areas where epigenetic inheritance systems have been discovered at the organismic level.JOURNAL, Bossdorf, Oliver, Arcuri, Davide, Richards, Christina L., Pigliucci, Massimo, Massimo Pigliucci, May 2010, Experimental alteration of DNA methylation affects the phenotypic plasticity of ecologically relevant traits in Arabidopsis thaliana, Evolutionary Ecology, 24, 3, 541–553, 10.1007/s10682-010-9372-7, 0269-7653,weblink {{harvnb|Jablonka|Lamb|2005}}{{page needed|date=December 2014}} Developmental biologists suggest that complex interactions in genetic networks and communication among cells can lead to heritable variations that may underlay some of the mechanics in developmental plasticity and canalisation.JOURNAL, Jablonka, Eva, Lamb, Marion J., December 2002, The Changing Concept of Epigenetics, Annals of the New York Academy of Sciences, 981, 1, 82–96, 2002NYASA.981...82J, 10.1111/j.1749-6632.2002.tb04913.x, 0077-8923, 12547675, Heritability may also occur at even larger scales. For example, ecological inheritance through the process of niche construction is defined by the regular and repeated activities of organisms in their environment. This generates a legacy of effects that modify and feed back into the selection regime of subsequent generations. Descendants inherit genes plus environmental characteristics generated by the ecological actions of ancestors.JOURNAL, Laland, Kevin N., Sterelny, Kim, Kim Sterelny, September 2006, Perspective: Seven Reasons (Not) to Neglect Niche Construction, Evolution (journal), Evolution, 60, 9, 1751–1762, 10.1111/j.0014-3820.2006.tb00520.x, 0014-3820, Other examples of heritability in evolution that are not under the direct control of genes include the inheritance of cultural traits and symbiogenesis.JOURNAL, Chapman, Michael J., Margulis, Lynn, Lynn Margulis, December 1998, Morphogenesis by symbiogenesis,weblink International Microbiology, 1, 4, 319–326, 1139-6709, 10943381, 2014-12-09, dead,weblink" title="">weblink 2014-08-23, JOURNAL, Wilson, David Sloan, David Sloan Wilson, Wilson, Edward O., E. O. Wilson, December 2007, Rethinking the Theoretical Foundation of Sociobiology,weblink The Quarterly Review of Biology, 82, 4, 327–348, 10.1086/522809, 0033-5770, 18217526, dead,weblink" title="">weblink 2011-05-11,


{{Multiple image|direction=vertical|align=right|image1=Biston.betularia.7200.jpg |image2=Biston.betularia.f.carbonaria.7209.jpg|width=200|caption1=White peppered moth |caption2=Black morph in peppered moth evolution}}{{Further|Genetic diversity|Population genetics}}An individual organism's phenotype results from both its genotype and the influence from the environment it has lived in. A substantial part of the phenotypic variation in a population is caused by genotypic variation. The modern evolutionary synthesis defines evolution as the change over time in this genetic variation. The frequency of one particular allele will become more or less prevalent relative to other forms of that gene. Variation disappears when a new allele reaches the point of fixation—when it either disappears from the population or replaces the ancestral allele entirely.JOURNAL, Amos, William, Harwood, John, February 28, 1998, Factors affecting levels of genetic diversity in natural populations, Philosophical Transactions of the Royal Society B, 353, 1366, 177–186, 10.1098/rstb.1998.0200, 0962-8436, 1692205, 9533122, Natural selection will only cause evolution if there is enough genetic variation in a population. Before the discovery of Mendelian genetics, one common hypothesis was blending inheritance. But with blending inheritance, genetic variance would be rapidly lost, making evolution by natural selection implausible. The Hardy–Weinberg principle provides the solution to how variation is maintained in a population with Mendelian inheritance. The frequencies of alleles (variations in a gene) will remain constant in the absence of selection, mutation, migration and genetic drift.{{harvnb|Ewens|2004}}{{page needed|date=December 2014}}Variation comes from mutations in the genome, reshuffling of genes through sexual reproduction and migration between populations (gene flow). Despite the constant introduction of new variation through mutation and gene flow, most of the genome of a species is identical in all individuals of that species.JOURNAL, Butlin, Roger K., Tregenza, Tom, February 28, 1998, Levels of genetic polymorphism: marker loci versus quantitative traits, Philosophical Transactions of the Royal Society B, 353, 1366, 187–198, 10.1098/rstb.1998.0201, 0962-8436, 1692210, 9533123,
  • JOURNAL, Butlin, Roger K., Tregenza, Tom, December 29, 2000, Correction for Butlin and Tregenza, Levels of genetic polymorphism: marker loci versus quantitative traits, Philosophical Transactions of the Royal Society B, 355, 1404, 10.1098/rstb.2000.2000, 0962-8436, Some of the values in table 1 on p. 193 were given incorrectly. The errors do not affect the conclusions drawn in the paper. The corrected table is reproduced below., 1865, However, even relatively small differences in genotype can lead to dramatic differences in phenotype: for example, chimpanzees and humans differ in only about 5% of their genomes.JOURNAL, Wetterbom, Anna, Sevov, Marie, Cavelier, Lucia, Bergström, Tomas F., November 2006, Comparative Genomic Analysis of Human and Chimpanzee Indicates a Key Role for Indels in Primate Evolution, Journal of Molecular Evolution, 63, 5, 682–690, 10.1007/s00239-006-0045-7, 0022-2844, 17075697, 2006JMolE..63..682W,


File:Gene-duplication.svg|thumb|upright|Duplication of part of a chromosomechromosomeMutations are changes in the DNA sequence of a cell's genome. When mutations occur, they may alter the product of a gene, or prevent the gene from functioning, or have no effect. Based on studies in the fly Drosophila melanogaster, it has been suggested that if a mutation changes a protein produced by a gene, this will probably be harmful, with about 70% of these mutations having damaging effects, and the remainder being either neutral or weakly beneficial.JOURNAL, Sawyer, Stanley A., Parsch, John, Zhang Zhi, Hartl, Daniel L., April 17, 2007, Prevalence of positive selection among nearly neutral amino acid replacements in Drosophila, Proc. Natl. Acad. Sci. U.S.A., 104, 16, 6504–6510, 2007PNAS..104.6504S, 10.1073/pnas.0701572104, 0027-8424, 1871816, 17409186, Mutations can involve large sections of a chromosome becoming duplicated (usually by genetic recombination), which can introduce extra copies of a gene into a genome.JOURNAL, Hastings, P. J., Lupski, James R., James R. Lupski, Rosenberg, Susan M., Ira, Grzegorz, August 2009, Mechanisms of change in gene copy number, Nature Reviews Genetics, 10, 8, 551–564, 10.1038/nrg2593, 1471-0056, 2864001, 19597530, Extra copies of genes are a major source of the raw material needed for new genes to evolve.{{harvnb|Carroll|Grenier|Weatherbee|2005}}{{page needed|date=December 2014}} This is important because most new genes evolve within gene families from pre-existing genes that share common ancestors.JOURNAL, Harrison, Paul M., Gerstein, Mark, Mark Bender Gerstein, May 17, 2002, Studying Genomes Through the Aeons: Protein Families, Pseudogenes and Proteome Evolution, Journal of Molecular Biology, 318, 5, 1155–1174, 10.1016/S0022-2836(02)00109-2, 0022-2836, 12083509, For example, the human eye uses four genes to make structures that sense light: three for colour vision and one for night vision; all four are descended from a single ancestral gene.JOURNAL, Bowmaker, James K., Evolution of colour vision in vertebrates, May 1998, Eye, 12, 3b, 541–547, 10.1038/eye.1998.143, 0950-222X, 9775215, New genes can be generated from an ancestral gene when a duplicate copy mutates and acquires a new function. This process is easier once a gene has been duplicated because it increases the redundancy of the system; one gene in the pair can acquire a new function while the other copy continues to perform its original function.JOURNAL, Gregory, T. Ryan, T. Ryan Gregory, Hebert, Paul D. N., Paul D. N. Hebert, April 1999, The Modulation of DNA Content: Proximate Causes and Ultimate Consequences,weblink Genome Research, 9, 4, 317–324, 10.1101/gr.9.4.317, 1088-9051, 10207154, 2014-12-11, live,weblink" title="">weblink 2014-08-23, 2019-10-18, JOURNAL, Hurles, Matthew, Gene Duplication: The Genomic Trade in Spare Parts, July 13, 2004, PLOS Biology, 2, 7, e206, 10.1371/journal.pbio.0020206, 1545-7885, 449868, 15252449, Other types of mutations can even generate entirely new genes from previously noncoding DNA.JOURNAL, Liu, Na, Okamura, Katsutomo, Tyler, David M., Phillips, Michael D., Chung, Wei-Jen, Lai, Eric C, October 2008, The evolution and functional diversification of animal microRNA genes, Cell Research, 18, 10, 985–996, 10.1038/cr.2008.278, 1001-0602, 2712117, 18711447, 3, JOURNAL, Siepel, Adam, Adam C. Siepel, October 2009, Darwinian alchemy: Human genes from noncoding DNA, Genome Research, 19, 10, 1693–1695, 10.1101/gr.098376.109, 1088-9051, 2765273, 19797681, The generation of new genes can also involve small parts of several genes being duplicated, with these fragments then recombining to form new combinations with new functions.JOURNAL, Orengo, Christine A., Thornton, Janet M., Janet Thornton, July 2005, Protein families and their evolution—a structural perspective, Annual Review of Biochemistry, 74, 867–900, 10.1146/annurev.biochem.74.082803.133029, 0066-4154, 15954844, JOURNAL, Long, Manyuan, Betrán, Esther, Thornton, Kevin, Wang, Wen, November 2003, The origin of new genes: glimpses from the young and old, Nature Reviews Genetics, 4, 11, 865–875, 10.1038/nrg1204, 1471-0056, 14634634, When new genes are assembled from shuffling pre-existing parts, domains act as modules with simple independent functions, which can be mixed together to produce new combinations with new and complex functions.JOURNAL, Wang, Minglei, Caetano-Anollés, Gustavo, Gustavo Caetano-Anolles, January 14, 2009, The Evolutionary Mechanics of Domain Organization in Proteomes and the Rise of Modularity in the Protein World, Structure (journal), Structure, 17, 1, 66–78, 10.1016/j.str.2008.11.008, 1357-4310, 19141283, For example, polyketide synthases are large enzymes that make antibiotics; they contain up to one hundred independent domains that each catalyse one step in the overall process, like a step in an assembly line.JOURNAL, Weissman, Kira J., Müller, Rolf, April 14, 2008, Protein–Protein Interactions in Multienzyme Megasynthetases, ChemBioChem, 9, 6, 826–848, 10.1002/cbic.200700751, 1439-4227, 18357594,

Sex and recombination

{{Further|Sexual reproduction|Genetic recombination|Evolution of sexual reproduction}}In asexual organisms, genes are inherited together, or linked, as they cannot mix with genes of other organisms during reproduction. In contrast, the offspring of sexual organisms contain random mixtures of their parents' chromosomes that are produced through independent assortment. In a related process called homologous recombination, sexual organisms exchange DNA between two matching chromosomes.JOURNAL, Radding, Charles M., December 1982, Homologous Pairing and Strand Exchange in Genetic Recombination, Annual Review of Genetics, 16, 405–437, 10.1146/, 0066-4197, 6297377, Recombination and reassortment do not alter allele frequencies, but instead change which alleles are associated with each other, producing offspring with new combinations of alleles.JOURNAL, Agrawal, Aneil F., September 5, 2006, Evolution of Sex: Why Do Organisms Shuffle Their Genotypes?, Current Biology, 16, 17, R696–R704, 10.1016/j.cub.2006.07.063, 0960-9822, 16950096, 1996CBio....6.1213A,, Sex usually increases genetic variation and may increase the rate of evolution.JOURNAL, Peters, Andrew D., Otto, Sarah P., June 2003, Liberating genetic variance through sex, BioEssays, 25, 6, 533–537, 10.1002/bies.10291, 0265-9247, 12766942, JOURNAL, Goddard, Matthew R., Godfray, H. Charles J., Charles Godfray, Burt, Austin, March 31, 2005, Sex increases the efficacy of natural selection in experimental yeast populations, Nature, 434, 7033, 636–640, 2005Natur.434..636G, 10.1038/nature03405, 0028-0836, 15800622, File:Evolsex-dia1a.png|thumb|upright=1.15|This diagram illustrates the twofold cost of sex. If each individual were to contribute to the same number of offspring (two), (a) the sexual population remains the same size each generation, where the (b) Asexual reproductionAsexual reproductionThe two-fold cost of sex was first described by John Maynard Smith.{{harvnb|Maynard Smith|1978}}{{page needed|date=December 2014}} The first cost is that in sexually dimorphic species only one of the two sexes can bear young. (This cost does not apply to hermaphroditic species, like most plants and many invertebrates.) The second cost is that any individual who reproduces sexually can only pass on 50% of its genes to any individual offspring, with even less passed on as each new generation passes.{{harvnb|Ridley|1993}}{{page needed|date=December 2014}} Yet sexual reproduction is the more common means of reproduction among eukaryotes and multicellular organisms. The Red Queen hypothesis has been used to explain the significance of sexual reproduction as a means to enable continual evolution and adaptation in response to coevolution with other species in an ever-changing environment.JOURNAL, Van Valen, Leigh, Leigh Van Valen, 1973, A New Evolutionary Law,weblink Evolutionary Theory, 1, 1–30, 0093-4755, 2014-12-24, dead,weblink 2014-12-22, JOURNAL, Hamilton, W. D., W. D. Hamilton, Axelrod, Robert, Robert Axelrod, Tanese, Reiko, May 1, 1990, Sexual reproduction as an adaptation to resist parasites (a review), Proc. Natl. Acad. Sci. U.S.A., 87, 9, 3566–3573, 1990PNAS...87.3566H, 10.1073/pnas.87.9.3566, 0027-8424, 2185476, 53943, {{harvnb|Birdsell|Wills|2003|pp=113–117}}

Gene flow

{{Further|Gene flow}}Gene flow is the exchange of genes between populations and between species.JOURNAL, Morjan, Carrie L., Rieseberg, Loren H., Loren H. Rieseberg, June 2004, How species evolve collectively: implications of gene flow and selection for the spread of advantageous alleles, Molecular Ecology, 13, 6, 1341–1356, 15140081, 10.1111/j.1365-294X.2004.02164.x, 0962-1083, 2600545, It can therefore be a source of variation that is new to a population or to a species. Gene flow can be caused by the movement of individuals between separate populations of organisms, as might be caused by the movement of mice between inland and coastal populations, or the movement of pollen between heavy-metal-tolerant and heavy-metal-sensitive populations of grasses.Gene transfer between species includes the formation of hybrid organisms and horizontal gene transfer. Horizontal gene transfer is the transfer of genetic material from one organism to another organism that is not its offspring; this is most common among bacteria.JOURNAL, Boucher, Yan, Douady, Christophe J., Papke, R. Thane, Walsh, David A., Boudreau, Mary Ellen R., Nesbo, Camilla L., Case, Rebecca J., Doolittle, W. Ford, December 2003, Lateral gene transfer and the origins of prokaryotic groups, Annual Review of Genetics, 37, 283–328, 10.1146/annurev.genet.37.050503.084247, 0066-4197, 14616063, 3, In medicine, this contributes to the spread of antibiotic resistance, as when one bacteria acquires resistance genes it can rapidly transfer them to other species.JOURNAL, Walsh, Timothy R., October 2006, Combinatorial genetic evolution of multiresistance, Current Opinion (Elsevier), Current Opinion in Microbiology, 9, 5, 476–482, 10.1016/j.mib.2006.08.009, 1369-5274, 16942901, Horizontal transfer of genes from bacteria to eukaryotes such as the yeast Saccharomyces cerevisiae and the adzuki bean weevil Callosobruchus chinensis has occurred.JOURNAL, Kondo, Natsuko, Nikoh, Naruo, Ijichi, Nobuyuki, Shimada, Masakazu, Fukatsu, Takema, October 29, 2002, Genome fragment of Wolbachia endosymbiont transferred to X chromosome of host insect, Proc. Natl. Acad. Sci. U.S.A., 99, 22, 14280–14285, 2002PNAS...9914280K, 10.1073/pnas.222228199, 0027-8424, 137875, 12386340, 3, JOURNAL, Sprague, George F., Jr., December 1991, Genetic exchange between kingdoms, Current Opinion (Elsevier), Current Opinion in Genetics & Development, 1, 4, 530–533, 10.1016/S0959-437X(05)80203-5, 0959-437X, 1822285, An example of larger-scale transfers are the eukaryotic bdelloid rotifers, which have received a range of genes from bacteria, fungi and plants.JOURNAL, Gladyshev, Eugene A., Meselson, Matthew, Matthew Meselson, Arkhipova, Irina R., May 30, 2008, Massive Horizontal Gene Transfer in Bdelloid Rotifers, Science (journal), Science, 320, 5880, 1210–1213, 2008Sci...320.1210G, 10.1126/science.1156407, 0036-8075, 18511688,weblink Viruses can also carry DNA between organisms, allowing transfer of genes even across biological domains.JOURNAL, Baldo, Angela M., McClure, Marcella A., September 1999, Evolution and Horizontal Transfer of dUTPase-Encoding Genes in Viruses and Their Hosts, Journal of Virology, 73, 9, 7710–7721, 0022-538X, 104298, 10438861, Large-scale gene transfer has also occurred between the ancestors of eukaryotic cells and bacteria, during the acquisition of chloroplasts and mitochondria. It is possible that eukaryotes themselves originated from horizontal gene transfers between bacteria and archaea.JOURNAL, Rivera, Maria C., Lake, James A., James A. Lake, September 9, 2004, The ring of life provides evidence for a genome fusion origin of eukaryotes, Nature, 431, 7005, 152–155, 2004Natur.431..152R, 10.1038/nature02848, 0028-0836, 15356622,


File:Mutation and selection diagram.svg|thumb|upright=1.35|MutationMutationFrom a neo-Darwinian perspective, evolution occurs when there are changes in the frequencies of alleles within a population of interbreeding organisms, for example, the allele for black colour in a population of moths becoming more common. Mechanisms that can lead to changes in allele frequencies include natural selection, genetic drift, gene flow and mutation bias.

Natural selection

{{Further|Sexual selection}}Evolution by means of natural selection is the process by which traits that enhance survival and reproduction become more common in successive generations of a population. It has often been called a "self-evident" mechanism because it necessarily follows from three simple facts:
  • Variation exists within populations of organisms with respect to morphology, physiology, and behaviour (phenotypic variation).
  • Different traits confer different rates of survival and reproduction (differential fitness).
  • These traits can be passed from generation to generation (heritability of fitness).
More offspring are produced than can possibly survive, and these conditions produce competition between organisms for survival and reproduction. Consequently, organisms with traits that give them an advantage over their competitors are more likely to pass on their traits to the next generation than those with traits that do not confer an advantage.JOURNAL, Hurst, Laurence D., Laurence Hurst, Fundamental concepts in genetics: genetics and the understanding of selection, February 2009, Nature Reviews Genetics, 10, 2, 83–93, 10.1038/nrg2506, 1471-0056, 19119264, This teleonomy is the quality whereby the process of natural selection creates and preserves traits that are seemingly fitted for the functional roles they perform.{{harvnb|Darwin|1859|loc=Chapter XIV}} Consequences of selection include nonrandom matingJOURNAL, Otto, Sarah P., Sarah Otto, Servedio, Maria R., Maria Servedio, Nuismer, Scott L., Frequency-Dependent Selection and the Evolution of Assortative Mating, Genetics, August 2008, 179, 4, 2091–2112, 0016-6731, 10.1534/genetics.107.084418, 2516082, 18660541, and genetic hitchhiking.The central concept of natural selection is the evolutionary fitness of an organism.JOURNAL, Orr, H. Allen, H. Allen Orr, August 2009, Fitness and its role in evolutionary genetics, Nature Reviews Genetics, 10, 8, 531–539, 10.1038/nrg2603, 2753274, 19546856, 1471-0056, Fitness is measured by an organism's ability to survive and reproduce, which determines the size of its genetic contribution to the next generation. However, fitness is not the same as the total number of offspring: instead fitness is indicated by the proportion of subsequent generations that carry an organism's genes.JOURNAL, Haldane, J.B.S., J. B. S. Haldane, March 14, 1959, The Theory of Natural Selection To-Day, Nature, 183, 4663, 710–713, 1959Natur.183..710H, 10.1038/183710a0, 0028-0836, 13644170, For example, if an organism could survive well and reproduce rapidly, but its offspring were all too small and weak to survive, this organism would make little genetic contribution to future generations and would thus have low fitness.If an allele increases fitness more than the other alleles of that gene, then with each generation this allele will become more common within the population. These traits are said to be "selected for." Examples of traits that can increase fitness are enhanced survival and increased fecundity. Conversely, the lower fitness caused by having a less beneficial or deleterious allele results in this allele becoming rarer—they are "selected against."JOURNAL, Lande, Russell, Russell Lande, Arnold, Stevan J., November 1983, The Measurement of Selection on Correlated Characters, Evolution, 37, 6, 1210–1226, 10.1111/j.1558-5646.1983.tb00236.x, 28556011, 0014-3820, 2408842, Importantly, the fitness of an allele is not a fixed characteristic; if the environment changes, previously neutral or harmful traits may become beneficial and previously beneficial traits become harmful. However, even if the direction of selection does reverse in this way, traits that were lost in the past may not re-evolve in an identical form (see Dollo's law).JOURNAL, Goldberg, Emma E., Igić, Boris, November 2008, On phylogenetic tests of irreversible evolution, Evolution, 62, 11, 2727–2741, 10.1111/j.1558-5646.2008.00505.x, 0014-3820, 18764918, JOURNAL, Collin, Rachel, Miglietta, Maria Pia, November 2008, Reversing opinions on Dollo's Law, Trends (journals), Trends in Ecology & Evolution, 23, 11, 602–609, 10.1016/j.tree.2008.06.013, 0169-5347, 18814933, However, a re-activation of dormant genes, as long as they have not been eliminated from the genome and were only suppressed perhaps for hundreds of generations, can lead to the re-occurrence of traits thought to be lost like hindlegs in dolphins, teeth in chickens, wings in wingless stick insects, tails and additional nipples in humans etc.JOURNAL, Tomić, Nenad, Meyer-Rochow, Victor Benno, 2011, Atavisms: Medical, Genetic, and Evolutionary Implications, Perspectives in Biology and Medicine, 54, 3, 332–353, 10.1353/pbm.2011.0034, 0031-5982, 21857125, "Throwbacks" such as these are known as atavisms.File:Genetic Distribution.svg|thumb|left|upright=1.45|These charts depict the different types of genetic selection. On each graph, the x-axis variable is the type of phenotypic trait and the y-axis variable is the number of organisms. Group A is the original population and Group B is the population after selection.· Graph 1 shows directional selection, in which a single extreme phenotype is favoured.· Graph 2 depicts stabilizing selection, where the intermediate phenotype is favoured over the extreme traits.· Graph 3 shows disruptive selectiondisruptive selectionNatural selection within a population for a trait that can vary across a range of values, such as height, can be categorised into three different types. The first is directional selection, which is a shift in the average value of a trait over time—for example, organisms slowly getting taller.JOURNAL, Hoekstra, Hopi E., Hoekstra, Jonathan M., Berrigan, David, Vignieri, Sacha N., Hoang, Amy, Hill, Caryl E., Beerli, Peter, Kingsolver, Joel G., July 31, 2001, Strength and tempo of directional selection in the wild, Proc. Natl. Acad. Sci. U.S.A., 98, 16, 9157–9160, 2001PNAS...98.9157H, 10.1073/pnas.161281098, 0027-8424, 55389, 11470913, 3, Secondly, disruptive selection is selection for extreme trait values and often results in two different values becoming most common, with selection against the average value. This would be when either short or tall organisms had an advantage, but not those of medium height. Finally, in stabilising selection there is selection against extreme trait values on both ends, which causes a decrease in variance around the average value and less diversity.JOURNAL, Felsenstein, Joseph, Joseph Felsenstein, November 1979, Excursions along the Interface between Disruptive and Stabilizing Selection, Genetics, 93, 3, 773–795, 0016-6731, 1214112, 17248980, This would, for example, cause organisms to eventually have a similar height.A special case of natural selection is sexual selection, which is selection for any trait that increases mating success by increasing the attractiveness of an organism to potential mates.JOURNAL, Andersson, Malte, Simmons, Leigh W., June 2006, Sexual selection and mate choice, Trends in Ecology & Evolution, 21, 6, 296–302, 16769428, 10.1016/j.tree.2006.03.015, 0169-5347,weblink live,weblink" title="">weblink 2013-03-09,, Traits that evolved through sexual selection are particularly prominent among males of several animal species. Although sexually favoured, traits such as cumbersome antlers, mating calls, large body size and bright colours often attract predation, which compromises the survival of individual males.JOURNAL, Kokko, Hanna, Hanna Kokko, Brooks, Robert, McNamara, John M., Houston, Alasdair I., July 7, 2002, The sexual selection continuum, Proceedings of the Royal Society#Proceedings of the Royal Society B, Proceedings of the Royal Society B, 269, 1498, 1331–1340, 10.1098/rspb.2002.2020, 0962-8452, 1691039, 12079655, JOURNAL, Quinn, Thomas P., Hendry, Andrew P., Buck, Gregory B., 2001, Balancing natural and sexual selection in sockeye salmon: interactions between body size, reproductive opportunity and vulnerability to predation by bears,weblink Evolutionary Ecology Research, 3, 917–937, 1522-0613, 2014-12-15, live,weblink" title="">weblink 2016-03-05, This survival disadvantage is balanced by higher reproductive success in males that show these hard-to-fake, sexually selected traits.JOURNAL, Hunt, John, Brooks, Robert, Jennions, Michael D., Smith, Michael J., Bentsen, Caroline L., Bussière, Luc F., December 23, 2004, High-quality male field crickets invest heavily in sexual display but die young, Nature, 432, 7020, 1024–1027, 2004Natur.432.1024H, 10.1038/nature03084, 0028-0836, 15616562, 3, Natural selection most generally makes nature the measure against which individuals and individual traits, are more or less likely to survive. "Nature" in this sense refers to an ecosystem, that is, a system in which organisms interact with every other element, physical as well as biological, in their local environment. Eugene Odum, a founder of ecology, defined an ecosystem as: "Any unit that includes all of the a given area interacting with the physical environment so that a flow of energy leads to clearly defined trophic structure, biotic diversity, and material cycles (i.e., exchange of materials between living and nonliving parts) within the system...."{{harvnb|Odum|1971|p=8}} Each population within an ecosystem occupies a distinct niche, or position, with distinct relationships to other parts of the system. These relationships involve the life history of the organism, its position in the food chain and its geographic range. This broad understanding of nature enables scientists to delineate specific forces which, together, comprise natural selection.Natural selection can act at different levels of organisation, such as genes, cells, individual organisms, groups of organisms and species.{{harvnb|Okasha|2006}}JOURNAL, Gould, Stephen Jay, Stephen Jay Gould, February 28, 1998, Gulliver's further travels: the necessity and difficulty of a hierarchical theory of selection, Philosophical Transactions of the Royal Society B, 353, 1366, 307–314, 10.1098/rstb.1998.0211, 0962-8436, 1692213, 9533127, JOURNAL, Mayr, Ernst, Ernst Mayr, March 18, 1997, The objects of selection, Proc. Natl. Acad. Sci. U.S.A., 94, 6, 2091–2094, 1997PNAS...94.2091M, 10.1073/pnas.94.6.2091, 0027-8424, 33654, 9122151, Selection can act at multiple levels simultaneously.{{harvnb|Maynard Smith|1998|pp=203–211; discussion 211–217}} An example of selection occurring below the level of the individual organism are genes called transposons, which can replicate and spread throughout a genome.JOURNAL, Hickey, Donal A., 1992, Evolutionary dynamics of transposable elements in prokaryotes and eukaryotes, Genetica, 86, 1–3, 269–274, 10.1007/BF00133725, 0016-6707, 1334911, Selection at a level above the individual, such as group selection, may allow the evolution of cooperation, as discussed below.JOURNAL, Gould, Stephen Jay, Lloyd, Elisabeth A., Elisabeth Lloyd, October 12, 1999, Individuality and adaptation across levels of selection: how shall we name and generalise the unit of Darwinism?, Proc. Natl. Acad. Sci. U.S.A., 96, 21, 11904–11909, 1999PNAS...9611904G, 10.1073/pnas.96.21.11904, 0027-8424, 18385, 10518549,

Genetic hitchhiking

{{Further|Genetic hitchhiking|Hill–Robertson effect|Selective sweep}}Recombination allows alleles on the same strand of DNA to become separated. However, the rate of recombination is low (approximately two events per chromosome per generation). As a result, genes close together on a chromosome may not always be shuffled away from each other and genes that are close together tend to be inherited together, a phenomenon known as linkage.JOURNAL, Lien, Sigbjørn, Szyda, Joanna, Schechinger, Birgit, Rappold, Gudrun, Arnheim, Norm, February 2000, Evidence for Heterogeneity in Recombination in the Human Pseudoautosomal Region: High Resolution Analysis by Sperm Typing and Radiation-Hybrid Mapping, American Journal of Human Genetics, 66, 2, 557–566, 10.1086/302754, 0002-9297, 1288109, 10677316, 3, This tendency is measured by finding how often two alleles occur together on a single chromosome compared to expectations, which is called their linkage disequilibrium. A set of alleles that is usually inherited in a group is called a haplotype. This can be important when one allele in a particular haplotype is strongly beneficial: natural selection can drive a selective sweep that will also cause the other alleles in the haplotype to become more common in the population; this effect is called genetic hitchhiking or genetic draft.JOURNAL, Barton, Nicholas H., Nick Barton, November 29, 2000, Genetic hitchhiking, Philosophical Transactions of the Royal Society B, 355, 1403, 1553–1562, 10.1098/rstb.2000.0716, 0962-8436, 1692896, 11127900, Genetic draft caused by the fact that some neutral genes are genetically linked to others that are under selection can be partially captured by an appropriate effective population size.

Genetic drift

{{Further|Genetic drift|Effective population size}}File:Allele-frequency.png|thumb|Simulation of genetic drift of 20 unlinked alleles in populations of 10 (top) and 100 (bottom). Drift to fixation is more rapid in the smaller population.]]Genetic drift is the random fluctuations of allele frequencies within a population from one generation to the next.{{harvnb|Futuyma|Kirkpatrick|2017|pp=55–66|loc=Chapter 3: Natural Selection and Adaptation}} When selective forces are absent or relatively weak, allele frequencies are equally likely to drift upward or downward at each successive generation because the alleles are subject to sampling error.JOURNAL, Masel, Joanna, October 25, 2011, Genetic drift, Current Biology, 21, 20, R837–R838, 10.1016/j.cub.2011.08.007, 0960-9822, 22032182, 1996CBio....6.1213A, This drift halts when an allele eventually becomes fixed, either by disappearing from the population or replacing the other alleles entirely. Genetic drift may therefore eliminate some alleles from a population due to chance alone. Even in the absence of selective forces, genetic drift can cause two separate populations that began with the same genetic structure to drift apart into two divergent populations with different sets of alleles.JOURNAL, Lande, Russell, 1989, Fisherian and Wrightian theories of speciation, Genome (journal), Genome, 31, 1, 221–227, 10.1139/g89-037, 0831-2796, 2687093, The neutral theory of molecular evolution proposed that most evolutionary changes are the result of the fixation of neutral mutations by genetic drift.JOURNAL, Kimura, Motoo, Motoo Kimura, 1991, The neutral theory of molecular evolution: a review of recent evidence, Journal of Human Genetics, Japanese Journal of Human Genetics, 66, 4, 367–386, 10.1266/jjg.66.367, 0021-504X, 1954033,weblink Hence, in this model, most genetic changes in a population are the result of constant mutation pressure and genetic drift.JOURNAL, Kimura, Motoo, 1989, The neutral theory of molecular evolution and the world view of the neutralists, Genome, 31, 1, 24–31, 10.1139/g89-009, 0831-2796, 2687096, This form of the neutral theory is now largely abandoned, since it does not seem to fit the genetic variation seen in nature.JOURNAL, Kreitman, Martin, Martin Kreitman, August 1996, The neutral theory is dead. Long live the neutral theory, BioEssays, 18, 8, 678–683; discussion 683, 10.1002/bies.950180812, 0265-9247, 8760341, JOURNAL, Leigh, E.G., Jr., November 2007, Neutral theory: a historical perspective, Journal of Evolutionary Biology, 20, 6, 2075–2091, 10.1111/j.1420-9101.2007.01410.x, 1010-061X, 17956380, However, a more recent and better-supported version of this model is the nearly neutral theory, where a mutation that would be effectively neutral in a small population is not necessarily neutral in a large population. Other alternative theories propose that genetic drift is dwarfed by other stochastic forces in evolution, such as genetic hitchhiking, also known as genetic draft.JOURNAL, Gillespie, John H., John H. Gillespie, November 2001, Is the population size of a species relevant to its evolution?, Evolution, 55, 11, 2161–2169, 10.1111/j.0014-3820.2001.tb00732.x, 0014-3820, 11794777, JOURNAL, Neher, Richard A., Shraiman, Boris I., August 2011, Genetic Draft and Quasi-Neutrality in Large Facultatively Sexual Populations, Genetics, 188, 4, 975–996, 10.1534/genetics.111.128876, 0016-6731, 3176096, 21625002, 1108.1635, 2011arXiv1108.1635N, The time for a neutral allele to become fixed by genetic drift depends on population size, with fixation occurring more rapidly in smaller populations.JOURNAL, Otto, Sarah P., Whitlock, Michael C., June 1997, The Probability of Fixation in Populations of Changing Size,weblink Genetics, 146, 2, 723–733, 0016-6731, 1208011, 9178020, 2014-12-18, live,weblink" title="">weblink 2015-03-19, The number of individuals in a population is not critical, but instead a measure known as the effective population size.JOURNAL, Charlesworth, Brian, Brian Charlesworth, March 2009, Fundamental concepts in genetics: effective population size and patterns of molecular evolution and variation, Nature Reviews Genetics, 10, 3, 195–205, 10.1038/nrg2526, 1471-0056, 19204717, The effective population is usually smaller than the total population since it takes into account factors such as the level of inbreeding and the stage of the lifecycle in which the population is the smallest. The effective population size may not be the same for every gene in the same population.JOURNAL, Cutter, Asher D., Choi, Jae Young, August 2010, Natural selection shapes nucleotide polymorphism across the genome of the nematode Caenorhabditis briggsae, Genome Research, 20, 8, 1103–1111, 10.1101/gr.104331.109, 1088-9051, 2909573, 20508143, harv, It is usually difficult to measure the relative importance of selection and neutral processes, including drift.JOURNAL, Mitchell-Olds, Thomas, Willis, John H., Goldstein, David B., David B. Goldstein (geneticist), November 2007, Which evolutionary processes influence natural genetic variation for phenotypic traits?, Nature Reviews Genetics, 8, 11, 845–856, 10.1038/nrg2207, 1471-0056, 17943192, The comparative importance of adaptive and non-adaptive forces in driving evolutionary change is an area of current research.JOURNAL, Nei, Masatoshi, Masatoshi Nei, December 2005, Selectionism and Neutralism in Molecular Evolution, Molecular Biology and Evolution, 22, 12, 2318–2342, 10.1093/molbev/msi242, 0737-4038, 1513187, 16120807,
  • JOURNAL, Nei, Masatoshi, May 2006, Selectionism and Neutralism in Molecular Evolution, Molecular Biology and Evolution, Erratum, 23, 5, 1095, 10.1093/molbev/msk009, 0737-4038,

Gene flow

{{Further|Gene flow|Hybrid (biology)|Horizontal gene transfer}}Gene flow involves the exchange of genes between populations and between species. The presence or absence of gene flow fundamentally changes the course of evolution. Due to the complexity of organisms, any two completely isolated populations will eventually evolve genetic incompatibilities through neutral processes, as in the Bateson-Dobzhansky-Muller model, even if both populations remain essentially identical in terms of their adaptation to the environment.If genetic differentiation between populations develops, gene flow between populations can introduce traits or alleles which are disadvantageous in the local population and this may lead to organisms within these populations evolving mechanisms that prevent mating with genetically distant populations, eventually resulting in the appearance of new species. Thus, exchange of genetic information between individuals is fundamentally important for the development of the Biological Species Concept (BSC).During the development of the modern synthesis, Sewall Wright developed his shifting balance theory, which regarded gene flow between partially isolated populations as an important aspect of adaptive evolution.JOURNAL, Wright, Sewall, Sewall Wright, 1932, The roles of mutation, inbreeding, crossbreeding and selection in evolution,weblink Proceedings of the VI International Congress of Genetrics, 1, 356–366, 2014-12-18, live,weblink" title="">weblink 2014-08-23, However, recently there has been substantial criticism of the importance of the shifting balance theory.JOURNAL, Coyne, Jerry A., Jerry Coyne, Barton, Nicholas H., Turelli, Michael, June 1997, Perspective: A Critique of Sewall Wright's Shifting Balance Theory of Evolution, Evolution, 51, 3, 643–671, 10.2307/2411143, 28568586, 0014-3820, 2411143,

Mutation bias

Mutation bias is usually conceived as a difference in expected rates for two different kinds of mutation, e.g., transition-transversion bias, GC-AT bias, deletion-insertion bias. This is related to the idea of developmental bias.HaldaneJOURNAL, Haldane, J.B.S., A Mathematical Theory of Natural and Artificial Selection, Part V: Selection and Mutation, Mathematical Proceedings of the Cambridge Philosophical Society, Proceedings of the Cambridge Philosophical Society, July 1927, 26, 7, 838–844, 10.1017/S0305004100015644, 1927PCPS...23..838H, and Fisher{{harvnb|Fisher|1930}} argued that, because mutation is a weak pressure easily overcome by selection, tendencies of mutation would be ineffectual except under conditions of neutral evolution or extraordinarily high mutation rates. This opposing-pressures argument was long used to dismiss the possibility of internal tendencies in evolution,JOURNAL, Yampolsky, Lev Y., Stoltzfus, Arlin, December 20, 2001, Bias in the introduction of variation as an orienting factor in evolution, Evolution & Development, 3, 2, 73–83, 10.1046/j.1525-142x.2001.003002073.x, until the molecular era prompted renewed interest in neutral evolution.Noboru SueokaJOURNAL, Sueoka, Noboru, April 1, 1962, On the Genetic Basis of Variation and Heterogeneity of DNA Base Composition, Proc. Natl. Acad. Sci. U.S.A., 48, 4, 582–592, 10.1073/pnas.48.4.582, 13918161, 220819, 1962PNAS...48..582S, and Ernst FreeseJOURNAL, Freese, Ernst, Ernst Freese, On the Evolution of the Base Composition of DNA, July 1962, Journal of Theoretical Biology, 3, 1, 82–101, 10.1016/S0022-5193(62)80005-8, proposed that systematic biases in mutation might be responsible for systematic differences in genomic GC composition between species. The identification of a GC-biased E. coli mutator strain in 1967,JOURNAL, Cox, Edward C., Yanofsky, Charles, Charles Yanofsky, Altered base ratios in the DNA of an Escherichia coli mutator strain, November 1, 1967, Proc. Natl. Acad. Sci. USA, 58, 5, 1895–1902, 10.1073/pnas.58.5.1895, 4866980, 223881, 1967PNAS...58.1895C, along with the proposal of the neutral theory, established the plausibility of mutational explanations for molecular patterns, which are now common in the molecular evolution literature.For instance, mutation biases are frequently invoked in models of codon usage.JOURNAL, Shah, Premal, Gilchrist, Michael A., Explaining complex codon usage patterns with selection for translational efficiency, mutation bias, and genetic drift, June 21, 2011, Proc. Natl. Acad. Sci. U.S.A., 108, 25, 10231–10236, 10.1073/pnas.1016719108, 21646514, 3121864, 2011PNAS..10810231S, Such models also include effects of selection, following the mutation-selection-drift model,JOURNAL, Bulmer, Michael G., Michael Bulmer, The selection-mutation-drift theory of synonymous codon usage, November 1991, Genetics (journal), Genetics, 129, 3, 897–907, 1752426, 1204756, which allows both for mutation biases and differential selection based on effects on translation. Hypotheses of mutation bias have played an important role in the development of thinking about the evolution of genome composition, including isochores.JOURNAL, Fryxell, Karl J., Zuckerkandl, Emile, Emile Zuckerkandl, Cytosine Deamination Plays a Primary Role in the Evolution of Mammalian Isochores, September 2000, Molecular Biology and Evolution, 17, 9, 1371–1383, 10.1093/oxfordjournals.molbev.a026420, 10958853, Different insertion vs. deletion biases in different taxa can lead to the evolution of different genome sizes.JOURNAL, Petrov, Dmitri A., Sangster, Todd A., Johnston, J. Spencer, Hartl, Daniel L., Shaw, Kerry L., February 11, 2000, Evidence for DNA Loss as a Determinant of Genome Size, Science, 287, 5455, 1060–1062, 2000Sci...287.1060P, 10.1126/science.287.5455.1060, 0036-8075, 10669421, 3, JOURNAL, Petrov, Dmitri A., May 2002, DNA loss and evolution of genome size in Drosophila, Genetica, 115, 1, 81–91, 10.1023/A:1016076215168, 0016-6707, 12188050, The hypothesis of Lynch regarding genome size relies on mutational biases toward increase or decrease in genome size.However, mutational hypotheses for the evolution of composition suffered a reduction in scope when it was discovered that (1) GC-biased gene conversion makes an important contribution to composition in diploid organisms such as mammalsJOURNAL, Duret, Laurent, Galtier, Nicolas, Biased Gene Conversion and the Evolution of Mammalian Genomic Landscapes, September 2009, Annual Reviews (publisher), Annual Review of Genomics and Human Genetics, 10, 285–311, 10.1146/annurev-genom-082908-150001, 19630562, and (2) bacterial genomes frequently have AT-biased mutation.JOURNAL, Hershberg, Ruth, Petrov, Dmitri A., Dmitri Petrov, Evidence That Mutation Is Universally Biased towards AT in Bacteria, September 9, 2010, PLOS Genetics, 6, 9, e1001115, 20838599, 2936535, 10.1371/journal.pgen.1001115, Contemporary thinking about the role of mutation biases reflects a different theory from that of Haldane and Fisher. More recent work showed that the original "pressures" theory assumes that evolution is based on standing variation: when evolution depends on the introduction of new alleles, mutational and developmental biases in introduction can impose biases on evolution without requiring neutral evolution or high mutation rates.Several recent studies report that the mutations implicated in adaptation reflect common mutation biasesJOURNAL, Stoltzfus, Arlin, McCandlish, David M., Mutational Biases Influence Parallel Adaptation, Molecular Biology and Evolution, September 2017, 34, 9, 2163–2172, 10.1093/molbev/msx180, 28645195, 5850294, JOURNAL, Payne, Joshua L., Menardo, Fabrizio, Trauner, Andrej, Borrell, Sonia, Gygli, Sebastian M., Loiseau, Chloe, Gagneux, Sebastien, Hall, Alex R., 3, Transition bias influences the evolution of antibiotic resistance in Mycobacterium tuberculosis, May 13, 2019, PLOS Biology, 17, 5, e3000265, 31083647, 6532934, 10.1371/journal.pbio.3000265, JOURNAL, Storz, Jay F., Natarajan, Chandrasekhar, Signore, Anthony V., Witt, Christopher C., McCandlish, David M., Stoltzfus, Arlin, 3, The role of mutation bias in adaptive molecular evolution: insights from convergent changes in protein function, July 22, 2019, Philosophical Transactions of the Royal Society B, 374, 1777, 20180238, 31154983, 6560279, 10.1098/rstb.2018.0238, though others dispute this interpretation.JOURNAL, Svensson, Erik I., Berger, David, The Role of Mutation Bias in Adaptive Evolution, Trends in Ecology & Evolution, May 1, 2019, 34, 5, 422–434, 10.1016/j.tree.2019.01.015, 31003616,


File:Kishony lab-The Evolution of Bacteria on a Mega-Plate.webm|thumb|upright=1.5|thumbtime=106|A visual demonstration of rapid antibiotic resistance evolution by E. coli growing across a plate with increasing concentrations of trimethoprimtrimethoprimEvolution influences every aspect of the form and behaviour of organisms. Most prominent are the specific behavioural and physical adaptations that are the outcome of natural selection. These adaptations increase fitness by aiding activities such as finding food, avoiding predators or attracting mates. Organisms can also respond to selection by cooperating with each other, usually by aiding their relatives or engaging in mutually beneficial symbiosis. In the longer term, evolution produces new species through splitting ancestral populations of organisms into new groups that cannot or will not interbreed.These outcomes of evolution are distinguished based on time scale as macroevolution versus microevolution. Macroevolution refers to evolution that occurs at or above the level of species, in particular speciation and extinction; whereas microevolution refers to smaller evolutionary changes within a species or population, in particular shifts in allele frequency and adaptation.JOURNAL, Scott, Eugenie C., Eugenie Scott, Matzke, Nicholas J., Nick Matzke, May 15, 2007, Biological design in science classrooms, Proc. Natl. Acad. Sci. U.S.A., 104, Suppl. 1, 8669–8676, 2007PNAS..104.8669S, 10.1073/pnas.0701505104, 0027-8424, 17494747, 1876445, In general, macroevolution is regarded as the outcome of long periods of microevolution.JOURNAL, Hendry, Andrew Paul, Kinnison, Michael T., November 2001, An introduction to microevolution: rate, pattern, process, Genetica, 112–113, 1, 1–8, 10.1023/A:1013368628607, 0016-6707, 11838760, Thus, the distinction between micro- and macroevolution is not a fundamental one—the difference is simply the time involved.JOURNAL, Leroi, Armand M., Armand Marie Leroi, March–April 2000, The scale independence of evolution, Evolution & Development, 2, 2, 67–77, 10.1046/j.1525-142x.2000.00044.x, 1520-541X, 11258392,, However, in macroevolution, the traits of the entire species may be important. For instance, a large amount of variation among individuals allows a species to rapidly adapt to new habitats, lessening the chance of it going extinct, while a wide geographic range increases the chance of speciation, by making it more likely that part of the population will become isolated. In this sense, microevolution and macroevolution might involve selection at different levels—with microevolution acting on genes and organisms, versus macroevolutionary processes such as species selection acting on entire species and affecting their rates of speciation and extinction.{{sfn|Gould|2002|pp=657–658}}JOURNAL, Gould, Stephen Jay, July 19, 1994, Tempo and mode in the macroevolutionary reconstruction of Darwinism, Proc. Natl. Acad. Sci. U.S.A., 91, 15, 6764–6771, 1994PNAS...91.6764G, 10.1073/pnas.91.15.6764, 0027-8424, 44281, 8041695, JOURNAL, Jablonski, David, David Jablonski, 2000, Micro- and macroevolution: scale and hierarchy in evolutionary biology and paleobiology, Paleobiology (journal), Paleobiology, 26, sp4, 15–52, 10.1666/0094-8373(2000)26[15:MAMSAH]2.0.CO;2, 0094-8373, A common misconception is that evolution has goals, long-term plans, or an innate tendency for "progress", as expressed in beliefs such as orthogenesis and evolutionism; realistically however, evolution has no long-term goal and does not necessarily produce greater complexity.JOURNAL, Dougherty, Michael J., July 20, 1998, Is the human race evolving or devolving?,weblink Scientific American, 0036-8733, 2015-09-11, live,weblink" title="">weblink 2014-05-06, WEB,weblink Claim CB932: Evolution of degenerate forms, July 22, 2003, Isaak, Mark, TalkOrigins Archive, The TalkOrigins Foundation, Inc., Houston, Texas, 2014-12-19, live,weblink" title="">weblink 2014-08-23, {{harvnb|Lane|1996|p=61}} Although complex species have evolved, they occur as a side effect of the overall number of organisms increasing and simple forms of life still remain more common in the biosphere.JOURNAL, Carroll, Sean B., Sean B. Carroll, February 22, 2001, Chance and necessity: the evolution of morphological complexity and diversity, Nature, 409, 6823, 1102–1109, 2001Natur.409.1102C, 10.1038/35059227, 0028-0836, 11234024, For example, the overwhelming majority of species are microscopic prokaryotes, which form about half the world's biomass despite their small size,JOURNAL, Whitman, William B., Coleman, David C., Wiebe, William J., June 9, 1998, Prokaryotes: The unseen majority, Proc. Natl. Acad. Sci. U.S.A., 95, 12, 6578–6583, 1998PNAS...95.6578W, 10.1073/pnas.95.12.6578, 0027-8424, 33863, 9618454, and constitute the vast majority of Earth's biodiversity.JOURNAL, Schloss, Patrick D., Handelsman, Jo, Jo Handelsman, December 2004, Status of the Microbial Census, Microbiology and Molecular Biology Reviews, 68, 4, 686–691, 10.1128/MMBR.68.4.686-691.2004, 1092-2172, 539005, 15590780, Simple organisms have therefore been the dominant form of life on Earth throughout its history and continue to be the main form of life up to the present day, with complex life only appearing more diverse because it is more noticeable.JOURNAL, Nealson, Kenneth H., January 1999, Post-Viking microbiology: new approaches, new data, new insights, Origins of Life and Evolution of Biospheres, 29, 1, 73–93, 10.1023/A:1006515817767, 0169-6149, 11536899, 1999OLEB...29...73N, Indeed, the evolution of microorganisms is particularly important to modern evolutionary research, since their rapid reproduction allows the study of experimental evolution and the observation of evolution and adaptation in real time.JOURNAL, Buckling, Angus, MacLean, R. Craig, Brockhurst, Michael A., Colegrave, Nick, February 12, 2009, The Beagle in a bottle, Nature, 457, 7231, 824–829, 2009Natur.457..824B, 10.1038/nature07892, 0028-0836, 19212400, JOURNAL, Elena, Santiago F., Lenski, Richard E., Richard Lenski, June 2003, Evolution experiments with microorganisms: the dynamics and genetic bases of adaptation, Nature Reviews Genetics, 4, 6, 457–469, 10.1038/nrg1088, 1471-0056, 12776215,


{{details|Adaptation}}File:Homology vertebrates-en.svg|thumb|upright=1.35|Homologous bones in the limbs of tetrapods. The bones of these animals have the same basic structure, but have been adapted for specific uses.]]Adaptation is the process that makes organisms better suited to their habitat.{{harvnb|Mayr|1982|p=483}}: "Adaptation... could no longer be considered a static condition, a product of a creative past and became instead a continuing dynamic process."The sixth edition of the Oxford Dictionary of Science (2010) defines adaptation as "Any change in the structure or functioning of successive generations of a population that makes it better suited to its environment." Also, the term adaptation may refer to a trait that is important for an organism's survival. For example, the adaptation of horses' teeth to the grinding of grass. By using the term adaptation for the evolutionary process and adaptive trait for the product (the bodily part or function), the two senses of the word may be distinguished. Adaptations are produced by natural selection.JOURNAL, Orr, H. Allen, February 2005, The genetic theory of adaptation: a brief history, Nature Reviews Genetics, 6, 2, 119–127, 10.1038/nrg1523, 1471-0056, 15716908, The following definitions are due to Theodosius Dobzhansky:
  1. Adaptation is the evolutionary process whereby an organism becomes better able to live in its habitat or habitats.{{harvnb|Dobzhansky|1968|pp=1–34}}
  2. Adaptedness is the state of being adapted: the degree to which an organism is able to live and reproduce in a given set of habitats.{{harvnb|Dobzhansky|1970|pp=4–6, 79–82, 84–87}}
  3. An adaptive trait is an aspect of the developmental pattern of the organism which enables or enhances the probability of that organism surviving and reproducing.JOURNAL, Dobzhansky, Theodosius, March 1956, Genetics of Natural Populations. XXV. Genetic Changes in Populations of Drosophila pseudoobscura and Drosophila persimilis in Some Localities in California, Evolution, 10, 1, 82–92, 10.2307/2406099, 0014-3820, 2406099,
Adaptation may cause either the gain of a new feature, or the loss of an ancestral feature. An example that shows both types of change is bacterial adaptation to antibiotic selection, with genetic changes causing antibiotic resistance by both modifying the target of the drug, or increasing the activity of transporters that pump the drug out of the cell.JOURNAL, Nakajima, Akira, Sugimoto, Yohko, Yoneyama, Hiroshi, Nakae, Taiji, June 2002, High-Level Fluoroquinolone Resistance in Pseudomonas aeruginosa Due to Interplay of the MexAB-OprM Efflux Pump and the DNA Gyrase Mutation, Microbiology and Immunology, 46, 6, 391–395, 10.1111/j.1348-0421.2002.tb02711.x, 1348-0421, 12153116, Other striking examples are the bacteria Escherichia coli evolving the ability to use citric acid as a nutrient in a long-term laboratory experiment,JOURNAL, Blount, Zachary D., Borland, Christina Z., Lenski, Richard E., June 10, 2008, Inaugural Article: Historical contingency and the evolution of a key innovation in an experimental population of Escherichia coli, Proc. Natl. Acad. Sci. U.S.A., 105, 23, 7899–7906, 2008PNAS..105.7899B, 10.1073/pnas.0803151105, 0027-8424, 2430337, 18524956, Flavobacterium evolving a novel enzyme that allows these bacteria to grow on the by-products of nylon manufacturing,JOURNAL, Okada, Hirosuke, Negoro, Seiji, Kimura, Hiroyuki, Nakamura, Shunichi, November 10, 1983, Evolutionary adaptation of plasmid-encoded enzymes for degrading nylon oligomers, Nature, 306, 5939, 203–206, 1983Natur.306..203O, 10.1038/306203a0, 0028-0836, 6646204, JOURNAL, Ohno, Susumu, Susumu Ohno, April 1984, Birth of a unique enzyme from an alternative reading frame of the preexisted, internally repetitious coding sequence, Proc. Natl. Acad. Sci. U.S.A., 81, 8, 2421–2425, 1984PNAS...81.2421O, 10.1073/pnas.81.8.2421, 0027-8424, 345072, 6585807, and the soil bacterium Sphingobium evolving an entirely new metabolic pathway that degrades the synthetic pesticide pentachlorophenol.JOURNAL, Copley, Shelley D., June 2000, Evolution of a metabolic pathway for degradation of a toxic xenobiotic: the patchwork approach, Trends (journals), Trends in Biochemical Sciences, 25, 6, 261–265, 10.1016/S0968-0004(00)01562-0, 0968-0004, 10838562, JOURNAL, Crawford, Ronald L., Jung, Carina M., Strap, Janice L., October 2007, The recent evolution of pentachlorophenol (PCP)-4-monooxygenase (PcpB) and associated pathways for bacterial degradation of PCP, Biodegradation (journal), Biodegradation, 18, 5, 525–539, 10.1007/s10532-006-9090-6, 0923-9820, 17123025, An interesting but still controversial idea is that some adaptations might increase the ability of organisms to generate genetic diversity and adapt by natural selection (increasing organisms' evolvability).JOURNAL, Eshel, Ilan, December 1973, Clone-Selection and Optimal Rates of Mutation, Applied Probability Trust, Journal of Applied Probability, 10, 4, 728–738, 10.2307/3212376, 1475-6072, 3212376, {{harvnb|Altenberg|1995|pp=205–259}}JOURNAL, Masel, Joanna, Bergman, Aviv, July 2003, The evolution of the evolvability properties of the yeast prion [PSI+], Evolution, 57, 7, 1498–1512, 10.1111/j.0014-3820.2003.tb00358.x, 0014-3820, 12940355, JOURNAL, Lancaster, Alex K., Bardill, J. Patrick, True, Heather L., Masel, Joanna, February 2010, The Spontaneous Appearance Rate of the Yeast Prion [PSI+] and Its Implications for the Evolution of the Evolvability Properties of the [PSI+] System, Genetics, 184, 2, 393–400, 10.1534/genetics.109.110213, 0016-6731, 2828720, 19917766, JOURNAL, Draghi, Jeremy, Wagner, Günter P., Günter P. Wagner, February 2008, Evolution of evolvability in a developmental model, Evolution, 62, 2, 301–315, 10.1111/j.1558-5646.2007.00303.x, 0014-3820, 18031304, File:Whale skeleton.png|upright=1.35|thumb|left|A baleen whale skeleton. Letters a and b label flipper bones, which were adapted from front leg bones, while c indicates (Vestigiality|vestigial]] leg bones, both suggesting an adaptation from land to sea.JOURNAL, Bejder, Lars, Hall, Brian K., Brian K. Hall, November 2002, Limbs in whales and limblessness in other vertebrates: mechanisms of evolutionary and developmental transformation and loss, Evolution & Development, 4, 6, 445–458, 10.1046/j.1525-142X.2002.02033.x, 1520-541X, 12492145, )Adaptation occurs through the gradual modification of existing structures. Consequently, structures with similar internal organisation may have different functions in related organisms. This is the result of a single ancestral structure being adapted to function in different ways. The bones within bat wings, for example, are very similar to those in mice feet and primate hands, due to the descent of all these structures from a common mammalian ancestor.JOURNAL, Young, Nathan M., HallgrÍmsson, Benedikt, December 2005, Serial homology and the evolution of mammalian limb covariation structure, Evolution, 59, 12, 2691–2704, 10.1554/05-233.1, 0014-3820, 16526515, However, since all living organisms are related to some extent,JOURNAL, Penny, David, Poole, Anthony, December 1999, The nature of the last universal common ancestor, Current Opinion in Genetics & Development, 9, 6, 672–677, 10.1016/S0959-437X(99)00020-9, 0959-437X, 10607605, even organs that appear to have little or no structural similarity, such as arthropod, squid and vertebrate eyes, or the limbs and wings of arthropods and vertebrates, can depend on a common set of homologous genes that control their assembly and function; this is called deep homology.JOURNAL, Hall, Brian K., August 2003, Descent with modification: the unity underlying homology and homoplasy as seen through an analysis of development and evolution, Biological Reviews, 78, 3, 409–433, 10.1017/S1464793102006097, 1464-7931, 14558591, JOURNAL, Shubin, Neil, Neil Shubin, Tabin, Clifford J., Clifford Tabin, Carroll, Sean B., February 12, 2009, Deep homology and the origins of evolutionary novelty, Nature, 457, 7231, 818–823, 2009Natur.457..818S, 10.1038/nature07891, 0028-0836, 19212399, During evolution, some structures may lose their original function and become vestigial structures.JOURNAL, Fong, Daniel F., Kane, Thomas C., Culver, David C., November 1995, Vestigialization and Loss of Nonfunctional Characters, Annual Review of Ecology and Systematics, 26, 249–268, 10.1146/, 1545-2069, Such structures may have little or no function in a current species, yet have a clear function in ancestral species, or other closely related species. Examples include pseudogenes,JOURNAL, ZhaoLei Zhang, Gerstein, Mark, August 2004, Large-scale analysis of pseudogenes in the human genome, Current Opinion in Genetics & Development, 14, 4, 328–335, 10.1016/j.gde.2004.06.003, 0959-437X, 15261647, the non-functional remains of eyes in blind cave-dwelling fish,JOURNAL, Jeffery, May–June 2005, William R., Adaptive Evolution of Eye Degeneration in the Mexican Blind Cavefish, Journal of Heredity, 96, 3, 185–196, 10.1093/jhered/esi028, 0022-1503, 15653557,, wings in flightless birds,JOURNAL, Maxwell, Erin E., Larsson, Hans C.E., May 2007, Osteology and myology of the wing of the Emu (Dromaius novaehollandiae) and its bearing on the evolution of vestigial structures, Journal of Morphology, 268, 5, 423–441, 10.1002/jmor.10527, 0362-2525, 17390336, the presence of hip bones in whales and snakes, and sexual traits in organisms that reproduce via asexual reproduction.JOURNAL, van der Kooi, Casper J., Schwander, Tanja, November 2014, On the fate of sexual traits under asexuality,weblink PDF, Biological Reviews, 89, 4, 805–819, 10.1111/brv.12078, 1464-7931, 24443922, 2015-08-05, live,weblink" title="">weblink 2015-07-23, Examples of vestigial structures in humans include wisdom teeth,JOURNAL, Silvestri, Anthony R., Jr., Singh, Iqbal, April 2003, The unresolved problem of the third molar: Would people be better off without it?,weblink Journal of the American Dental Association, 134, 4, 450–455, 10.14219/jada.archive.2003.0194, 0002-8177, 12733778,weblink" title="">weblink 2014-08-23, dead, the coccyx, the vermiform appendix, and other behavioural vestiges such as goose bumps{{harvnb|Coyne|2009|p=62}}{{harvnb|Darwin|1872|pp=101, 103}} and primitive reflexes.{{harvnb|Gray|2007|p=66}}{{harvnb|Coyne|2009|pp=85–86}}{{harvnb|Stevens|1982|p=87}}However, many traits that appear to be simple adaptations are in fact exaptations: structures originally adapted for one function, but which coincidentally became somewhat useful for some other function in the process.{{sfn|Gould|2002|pp=1235–1236}} One example is the African lizard Holaspis guentheri, which developed an extremely flat head for hiding in crevices, as can be seen by looking at its near relatives. However, in this species, the head has become so flattened that it assists in gliding from tree to tree—an exaptation.{{sfn|Gould|2002|pp=1235–1236}} Within cells, molecular machines such as the bacterial flagellaJOURNAL, Pallen, Mark J., Matzke, Nicholas J., October 2006, From The Origin of Species to the origin of bacterial flagella,weblink PDF, Nature Reviews Microbiology, 4, 10, 784–790, 10.1038/nrmicro1493, 1740-1526, 16953248, 2014-12-25, dead,weblink 2014-12-26, and protein sorting machineryJOURNAL, Clements, Abigail, Bursac, Dejan, Gatsos, Xenia, Perry, Andrew J., Civciristov, Srgjan, Celik, Nermin, Likic, Vladimir A., Poggio, Sebastian, Jacobs-Wagner, Christine, Strugnell, Richard A., Lithgow, Trevor, September 15, 2009, The reducible complexity of a mitochondrial molecular machine, Proc. Natl. Acad. Sci. U.S.A., 106, 37, 15791–15795, 2009PNAS..10615791C, 10.1073/pnas.0908264106, 0027-8424, 19717453, 2747197, 3, evolved by the recruitment of several pre-existing proteins that previously had different functions. Another example is the recruitment of enzymes from glycolysis and xenobiotic metabolism to serve as structural proteins called crystallins within the lenses of organisms' eyes.{{harvnb|Piatigorsky|Kantorow|Gopal-Srivastava|Tomarev|1994|pp=241–250}}JOURNAL, Wistow, Graeme, August 1993, Lens crystallins: gene recruitment and evolutionary dynamism, Trends in Biochemical Sciences, 18, 8, 301–306, 10.1016/0968-0004(93)90041-K, 0968-0004, 8236445, An area of current investigation in evolutionary developmental biology is the developmental basis of adaptations and exaptations.JOURNAL, Johnson, Norman A., Porter, Adam H., November 2001, Toward a new synthesis: population genetics and evolutionary developmental biology, Genetica, 112–113, 1, 45–58, 10.1023/A:1013371201773, 0016-6707, 11838782, This research addresses the origin and evolution of embryonic development and how modifications of development and developmental processes produce novel features.JOURNAL, Baguñà, Jaume, Garcia-Fernàndez, Jordi, 2003, Evo-Devo: the long and winding road,weblink The International Journal of Developmental Biology, 47, 7–8, 705–713, 0214-6282, 14756346, live,weblink" title="">weblink 2014-11-28,
  • JOURNAL, Love, Alan C., March 2003, Evolutionary Morphology, Innovation and the Synthesis of Evolutionary and Developmental Biology, Biology and Philosophy, 18, 2, 309–345, 10.1023/A:1023940220348, 0169-3867, These studies have shown that evolution can alter development to produce new structures, such as embryonic bone structures that develop into the jaw in other animals instead forming part of the middle ear in mammals.JOURNAL, Allin, Edgar F., December 1975, Evolution of the mammalian middle ear, Journal of Morphology, 147, 4, 403–437, 10.1002/jmor.1051470404, 0362-2525, 1202224, It is also possible for structures that have been lost in evolution to reappear due to changes in developmental genes, such as a mutation in chickens causing embryos to grow teeth similar to those of crocodiles.JOURNAL, Harris, Matthew P., Hasso, Sean M., Ferguson, Mark W.J., Fallon, John F., February 21, 2006, The Development of Archosaurian First-Generation Teeth in a Chicken Mutant, Current Biology, 16, 4, 371–377, 10.1016/j.cub.2005.12.047, 0960-9822, 16488870, 1996CBio....6.1213A, It is now becoming clear that most alterations in the form of organisms are due to changes in a small set of conserved genes.JOURNAL, Carroll, Sean B., July 11, 2008, Evo-Devo and an Expanding Evolutionary Synthesis: A Genetic Theory of Morphological Evolution, Cell (journal), Cell, 134, 1, 25–36, 10.1016/j.cell.2008.06.030, 0092-8674, 18614008,


File:Thamnophis sirtalis sirtalis Wooster.jpg|thumb|Common garter snake (Thamnophis sirtalis sirtalis) has evolved resistance to the defensive substance tetrodotoxintetrodotoxin{{Further|Coevolution}}Interactions between organisms can produce both conflict and cooperation. When the interaction is between pairs of species, such as a pathogen and a host, or a predator and its prey, these species can develop matched sets of adaptations. Here, the evolution of one species causes adaptations in a second species. These changes in the second species then, in turn, cause new adaptations in the first species. This cycle of selection and response is called coevolution.JOURNAL, Wade, Michael J., Michael J. Wade, March 2007, The co-evolutionary genetics of ecological communities, Nature Reviews Genetics, 8, 3, 185–195, 10.1038/nrg2031, 1471-0056, 17279094, An example is the production of tetrodotoxin in the rough-skinned newt and the evolution of tetrodotoxin resistance in its predator, the common garter snake. In this predator-prey pair, an evolutionary arms race has produced high levels of toxin in the newt and correspondingly high levels of toxin resistance in the snake.JOURNAL, Geffeney, Shana, Brodie, Edmund D., Jr., Ruben, Peter C., Brodie, Edmund D., III, August 23, 2002, Mechanisms of Adaptation in a Predator-Prey Arms Race: TTX-Resistant Sodium Channels, Science, 297, 5585, 1336–1339, 2002Sci...297.1336G, 10.1126/science.1074310, 0036-8075, 12193784,
  • JOURNAL, Brodie, Edmund D., Jr., Ridenhour, Benjamin J., Brodie, Edmund D., III, October 2002, The evolutionary response of predators to dangerous prey: hotspots and coldspots in the geographic mosaic of coevolution between garter snakes and newts, Evolution, 56, 10, 2067–2082, 10.1554/0014-3820(2002)056[2067:teropt];2, 0014-3820, 12449493,
  • NEWS, Carroll, Sean B., December 21, 2009, Whatever Doesn't Kill Some Animals Can Make Them Deadly,weblink The New York Times, New York, The New York Times Company, 0362-4331, 2014-12-26, live,weblink" title="">weblink 2015-04-23,


{{Further|Co-operation (evolution)}}Not all co-evolved interactions between species involve conflict.JOURNAL, Sachs, Joel L., September 2006, Cooperation within and among species, Journal of Evolutionary Biology, 19, 5, 1415–1418; discussion 1426–1436, 10.1111/j.1420-9101.2006.01152.x, 1010-061X, 16910971,
  • JOURNAL, Nowak, Martin A., Martin Nowak, December 8, 2006, Five Rules for the Evolution of Cooperation, Science, 314, 5805, 1560–1563, 2006Sci...314.1560N, 10.1126/science.1133755, 0036-8075, 3279745, 17158317, Many cases of mutually beneficial interactions have evolved. For instance, an extreme cooperation exists between plants and the mycorrhizal fungi that grow on their roots and aid the plant in absorbing nutrients from the soil.JOURNAL, Paszkowski, Uta, August 2006, Mutualism and parasitism: the yin and yang of plant symbioses, Current Opinion (Elsevier), Current Opinion in Plant Biology, 9, 4, 364–370, 10.1016/j.pbi.2006.05.008, 1369-5266, 16713732, This is a reciprocal relationship as the plants provide the fungi with sugars from photosynthesis. Here, the fungi actually grow inside plant cells, allowing them to exchange nutrients with their hosts, while sending signals that suppress the plant immune system.JOURNAL, Hause, Bettina, Fester, Thomas, May 2005, Molecular and cell biology of arbuscular mycorrhizal symbiosis, Planta (journal), Planta, 221, 2, 184–196, 10.1007/s00425-004-1436-x, 0032-0935, 15871030,
Coalitions between organisms of the same species have also evolved. An extreme case is the eusociality found in social insects, such as bees, termites and ants, where sterile insects feed and guard the small number of organisms in a colony that are able to reproduce. On an even smaller scale, the somatic cells that make up the body of an animal limit their reproduction so they can maintain a stable organism, which then supports a small number of the animal's germ cells to produce offspring. Here, somatic cells respond to specific signals that instruct them whether to grow, remain as they are, or die. If cells ignore these signals and multiply inappropriately, their uncontrolled growth causes cancer.JOURNAL, Bertram, John S., December 2000, The molecular biology of cancer, Molecular Aspects of Medicine, 21, 6, 167–223, 10.1016/S0098-2997(00)00007-8, 0098-2997, 11173079, Such cooperation within species may have evolved through the process of kin selection, which is where one organism acts to help raise a relative's offspring.JOURNAL, Reeve, H. Kern, Hölldobler, Bert, Bert Hölldobler, June 5, 2007, The emergence of a superorganism through intergroup competition, Proc. Natl. Acad. Sci. U.S.A., 104, 23, 9736–9740, 2007PNAS..104.9736R, 10.1073/pnas.0703466104, 0027-8424, 1887545, 17517608, This activity is selected for because if the helping individual contains alleles which promote the helping activity, it is likely that its kin will also contain these alleles and thus those alleles will be passed on.JOURNAL, Axelrod, Robert, Hamilton, W. D., March 27, 1981, The evolution of cooperation, Science, 211, 4489, 1390–1396, 1981Sci...211.1390A, 10.1126/science.7466396, 0036-8075, 7466396, Other processes that may promote cooperation include group selection, where cooperation provides benefits to a group of organisms.JOURNAL, Wilson, Edward O., Hölldobler, Bert, September 20, 2005, Eusociality: Origin and consequences, Proc. Natl. Acad. Sci. U.S.A., 102, 38, 13367–1371, 2005PNAS..10213367W, 10.1073/pnas.0505858102, 0027-8424, 1224642, 16157878,


{{Further|Assortative mating|Panmixia}}File:Speciation modes edit.svg|left|thumb|upright=1.6|The four geographic modes of speciationspeciationSpeciation is the process where a species diverges into two or more descendant species.JOURNAL, Gavrilets, Sergey, October 2003, Perspective: models of speciation: what have we learned in 40 years?, Evolution, 57, 10, 2197–2215, 10.1554/02-727, 0014-3820, 14628909, There are multiple ways to define the concept of "species." The choice of definition is dependent on the particularities of the species concerned.JOURNAL, de Queiroz, Kevin, May 3, 2005, Ernst Mayr and the modern concept of species, Proc. Natl. Acad. Sci. U.S.A., 102, Suppl. 1, 6600–6607, 2005PNAS..102.6600D, 10.1073/pnas.0502030102, 0027-8424, 1131873, 15851674, For example, some species concepts apply more readily toward sexually reproducing organisms while others lend themselves better toward asexual organisms. Despite the diversity of various species concepts, these various concepts can be placed into one of three broad philosophical approaches: interbreeding, ecological and phylogenetic.JOURNAL, Ereshefsky, Marc, Marc Ereshefsky, December 1992, Eliminative pluralism, Philosophy of Science (journal), Philosophy of Science, 59, 4, 671–690, 10.1086/289701, 0031-8248, 188136, The Biological Species Concept (BSC) is a classic example of the interbreeding approach. Defined by evolutionary biologist Ernst Mayr in 1942, the BSC states that "species are groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups."{{harvnb|Mayr|1942|p=120}} Despite its wide and long-term use, the BSC like others is not without controversy, for example because these concepts cannot be applied to prokaryotes,JOURNAL, Fraser, Christophe, Alm, Eric J., Polz, Martin F., Spratt, Brian G., Hanage, William P., February 6, 2009, The Bacterial Species Challenge: Making Sense of Genetic and Ecological Diversity, Science, 323, 5915, 741–746, 2009Sci...323..741F, 10.1126/science.1159388, 0036-8075, 19197054, 3, and this is called the species problem. Some researchers have attempted a unifying monistic definition of species, while others adopt a pluralistic approach and suggest that there may be different ways to logically interpret the definition of a species.Barriers to reproduction between two diverging sexual populations are required for the populations to become new species. Gene flow may slow this process by spreading the new genetic variants also to the other populations. Depending on how far two species have diverged since their most recent common ancestor, it may still be possible for them to produce offspring, as with horses and donkeys mating to produce mules.JOURNAL, Short, Roger Valentine, October 1975, The contribution of the mule to scientific thought, Journal of Reproduction and Fertility. Supplement, 23, 359–364, 0449-3087, 1639439, 1107543, Such hybrids are generally infertile. In this case, closely related species may regularly interbreed, but hybrids will be selected against and the species will remain distinct. However, viable hybrids are occasionally formed and these new species can either have properties intermediate between their parent species, or possess a totally new phenotype.JOURNAL, Gross, Briana L., Rieseberg, Loren H., May–June 2005, The Ecological Genetics of Homoploid Hybrid Speciation, Journal of Heredity, 96, 3, 241–252, 10.1093/jhered/esi026, 0022-1503, 2517139, 15618301, The importance of hybridisation in producing new species of animals is unclear, although cases have been seen in many types of animals,JOURNAL, Burke, John M., Arnold, Michael L., December 2001, Genetics and the fitness of hybrids, Annual Review of Genetics, 35, 31–52, 10.1146/annurev.genet.35.102401.085719, 0066-4197, 11700276, with the gray tree frog being a particularly well-studied example.JOURNAL, Vrijenhoek, Robert C., April 4, 2006, Polyploid Hybrids: Multiple Origins of a Treefrog Species, Current Biology, 16, 7, R245–R247, 10.1016/j.cub.2006.03.005, 0960-9822, 16581499, 1996CBio....6.1213A, Speciation has been observed multiple times under both controlled laboratory conditions (see laboratory experiments of speciation) and in nature.JOURNAL, Rice, William R., Hostert, Ellen E., December 1993, Laboratory Experiments on Speciation: What Have We Learned in 40 Years?, Evolution, 47, 6, 1637–1653, 10.1111/j.1558-5646.1993.tb01257.x, 28568007, 0014-3820, 2410209,
  • JOURNAL, Jiggins, Chris D., Bridle, Jon R., March 2004, Speciation in the apple maggot fly: a blend of vintages?, Trends in Ecology & Evolution, 19, 3, 111–114, 10.1016/j.tree.2003.12.008, 16701238, 0169-5347,
  • WEB,weblink Observed Instances of Speciation, Boxhorn, Joseph, September 1, 1995, TalkOrigins Archive, The TalkOrigins Foundation, Inc., Houston, Texas, 2008-12-26, live,weblink" title="">weblink 2009-01-22,
  • JOURNAL, Weinberg, James R., Starczak, Victoria R., Jörg, Daniele, August 1992, Evidence for Rapid Speciation Following a Founder Event in the Laboratory, Evolution, 46, 4, 1214–1220, 10.2307/2409766, 28564398, 0014-3820, 2409766, In sexually reproducing organisms, speciation results from reproductive isolation followed by genealogical divergence. There are four primary geographic modes of speciation. The most common in animals is allopatric speciation, which occurs in populations initially isolated geographically, such as by habitat fragmentation or migration. Selection under these conditions can produce very rapid changes in the appearance and behaviour of organisms.JOURNAL, Herrel, Anthony, Huyghe, Katleen, Vanhooydonck, Bieke, Backeljau, Thierry, Breugelmans, Karin, Grbac, Irena, Van Damme, Raoul, Irschick, Duncan J., March 25, 2008, Rapid large-scale evolutionary divergence in morphology and performance associated with exploitation of a different dietary resource, Proc. Natl. Acad. Sci. U.S.A., 105, 12, 4792–4795, 2008PNAS..105.4792H, 10.1073/pnas.0711998105, 0027-8424, 2290806, 18344323, 3, JOURNAL, Losos, Jonathan B., Warhelt, Kenneth I., Schoener, Thomas W., May 1, 1997, Adaptive differentiation following experimental island colonization in Anolis lizards, Nature, 387, 6628, 70–73, 1997Natur.387...70L, 10.1038/387070a0, 0028-0836, As selection and drift act independently on populations isolated from the rest of their species, separation may eventually produce organisms that cannot interbreed.JOURNAL, Hoskin, Conrad J., Higgle, Megan, McDonald, Keith R., Moritz, Craig, October 27, 2005, Reinforcement drives rapid allopatric speciation, Nature, 16251964, 437, 7063, 1353–1356, 2005Natur.437.1353H, 10.1038/nature04004, 0028-0836,
The second mode of speciation is peripatric speciation, which occurs when small populations of organisms become isolated in a new environment. This differs from allopatric speciation in that the isolated populations are numerically much smaller than the parental population. Here, the founder effect causes rapid speciation after an increase in inbreeding increases selection on homozygotes, leading to rapid genetic change.JOURNAL, Templeton, Alan R., Alan Templeton, April 1980, The Theory of Speciation VIA the Founder Principle,weblink Genetics, 94, 4, 1011–1038, 6777243, 0016-6731, 1214177, 2014-12-29, live,weblink" title="">weblink 2014-08-23, The third mode is parapatric speciation. This is similar to peripatric speciation in that a small population enters a new habitat, but differs in that there is no physical separation between these two populations. Instead, speciation results from the evolution of mechanisms that reduce gene flow between the two populations. Generally this occurs when there has been a drastic change in the environment within the parental species' habitat. One example is the grass Anthoxanthum odoratum, which can undergo parapatric speciation in response to localised metal pollution from mines.JOURNAL, Antonovics, Janis, Janis Antonovics, July 2006, Evolution in closely adjacent plant populations X: long-term persistence of prereproductive isolation at a mine boundary, Heredity (journal), Heredity, 97, 1, 33–37, 10.1038/sj.hdy.6800835, 0018-067X, 16639420, Here, plants evolve that have resistance to high levels of metals in the soil. Selection against interbreeding with the metal-sensitive parental population produced a gradual change in the flowering time of the metal-resistant plants, which eventually produced complete reproductive isolation. Selection against hybrids between the two populations may cause reinforcement, which is the evolution of traits that promote mating within a species, as well as character displacement, which is when two species become more distinct in appearance.JOURNAL, Nosil, Patrik, Crespi, Bernard J., Gries, Regine, Gries, Gerhard, March 2007, Natural selection and divergence in mate preference during speciation, Genetica, 129, 3, 309–327, 10.1007/s10709-006-0013-6, 16900317, 0016-6707, File:Darwin's finches.jpeg|frame|Geographical isolation of finches on the Galápagos IslandsGalápagos IslandsFinally, in sympatric speciation species diverge without geographic isolation or changes in habitat. This form is rare since even a small amount of gene flow may remove genetic differences between parts of a population.JOURNAL, Savolainen, Vincent, Anstett, Marie-Charlotte, Lexer, Christian, Hutton, Ian, Clarkson, James J., Norup, Maria V., Powell, Martyn P., Springate, David, Salamin, Nicolas, Baker, William J., May 11, 2006, Sympatric speciation in palms on an oceanic island, Nature, 441, 7090, 210–213, 2006Natur.441..210S, 10.1038/nature04566, 0028-0836, 16467788, 3,
  • JOURNAL, Barluenga, Marta, Stölting, Kai N., Salzburger, Walter, Muschick, Moritz, Meyer, Axel, Axel Meyer, February 9, 2006, Sympatric speciation in Nicaraguan crater lake cichlid fish, Nature, 439, 7077, 719–23, 2006Natur.439..719B, 10.1038/nature04325, 0028-0836, 16467837, 3,weblink Generally, sympatric speciation in animals requires the evolution of both genetic differences and nonrandom mating, to allow reproductive isolation to evolve.JOURNAL, Gavrilets, Sergey, March 21, 2006, The Maynard Smith model of sympatric speciation, Journal of Theoretical Biology, 239, 2, 172–182, 10.1016/j.jtbi.2005.08.041, 0022-5193, 16242727,
One type of sympatric speciation involves crossbreeding of two related species to produce a new hybrid species. This is not common in animals as animal hybrids are usually sterile. This is because during meiosis the homologous chromosomes from each parent are from different species and cannot successfully pair. However, it is more common in plants because plants often double their number of chromosomes, to form polyploids.JOURNAL, Wood, Troy E., Takebayashi, Naoki, Barker, Michael S., Mayrose, Itay, Greenspoon, Philip B., Rieseberg, Loren H., August 18, 2009, The frequency of polyploid speciation in vascular plants, Proc. Natl. Acad. Sci. U.S.A., 106, 33, 13875–13879, 2009PNAS..10613875W, 10.1073/pnas.0811575106, 0027-8424, 2728988, 19667210, 3, This allows the chromosomes from each parental species to form matching pairs during meiosis, since each parent's chromosomes are represented by a pair already.JOURNAL, Hegarty, Matthew J., Hiscock, Simon J., May 20, 2008, Genomic Clues to the Evolutionary Success of Polyploid Plants, Current Biology, 18, 10, R435–R444, 10.1016/j.cub.2008.03.043, 0960-9822, 18492478, 1996CBio....6.1213A, An example of such a speciation event is when the plant species Arabidopsis thaliana and Arabidopsis arenosa crossbred to give the new species Arabidopsis suecica.JOURNAL, Jakobsson, Mattias, Hagenblad, Jenny, Tavaré, Simon, Simon Tavaré, Säll, Torbjörn, Halldén, Christer, Lind-Halldén, Christina, Nordborg, Magnus, June 2006, A Unique Recent Origin of the Allotetraploid Species Arabidopsis suecica: Evidence from Nuclear DNA Markers, Molecular Biology and Evolution, 23, 6, 1217–1231, 10.1093/molbev/msk006, 0737-4038, 16549398, 3,weblink This happened about 20,000 years ago,JOURNAL, Säll, Torbjörn, Jakobsson, Mattias, Lind-Halldén, Christina, Halldén, Christer, September 2003, Chloroplast DNA indicates a single origin of the allotetraploid Arabidopsis suecica, Journal of Evolutionary Biology, 16, 5, 1019–1029, 10.1046/j.1420-9101.2003.00554.x, 1010-061X, 14635917, and the speciation process has been repeated in the laboratory, which allows the study of the genetic mechanisms involved in this process.JOURNAL, Bomblies, Kirsten, Kirsten Bomblies, Weigel, Detlef, Detlef Weigel, December 2007, Arabidopsis—a model genus for speciation, Current Opinion in Genetics & Development, 17, 6, 500–504, 10.1016/j.gde.2007.09.006, 0959-437X, 18006296, Indeed, chromosome doubling within a species may be a common cause of reproductive isolation, as half the doubled chromosomes will be unmatched when breeding with undoubled organisms.JOURNAL, Sémon, Marie, Wolfe, Kenneth H., December 2007, Consequences of genome duplication, Current Opinion in Genetics & Development, 17, 6, 505–512, 10.1016/j.gde.2007.09.007, 0959-437X, 18006297, Speciation events are important in the theory of punctuated equilibrium, which accounts for the pattern in the fossil record of short "bursts" of evolution interspersed with relatively long periods of stasis, where species remain relatively unchanged.{{harvnb|Eldredge|Gould|1972|pp=82–115}} In this theory, speciation and rapid evolution are linked, with natural selection and genetic drift acting most strongly on organisms undergoing speciation in novel habitats or small populations. As a result, the periods of stasis in the fossil record correspond to the parental population and the organisms undergoing speciation and rapid evolution are found in small populations or geographically restricted habitats and therefore rarely being preserved as fossils.


{{Further|Extinction}}File:Palais de la Decouverte Tyrannosaurus rex p1050042.jpg|thumb|left|Tyrannosaurus rex. Non-avian dinosaurs died out in the Cretaceous–Paleogene extinction event at the end of the CretaceousCretaceousExtinction is the disappearance of an entire species. Extinction is not an unusual event, as species regularly appear through speciation and disappear through extinction.JOURNAL, Benton, Michael J., Michael Benton, April 7, 1995, Diversification and extinction in the history of life, Science, 268, 5207, 52–58, 1995Sci...268...52B, 10.1126/science.7701342, 0036-8075, 7701342, Nearly all animal and plant species that have lived on Earth are now extinct,JOURNAL, Raup, David M., David M. Raup, March 28, 1986, Biological extinction in Earth history, Science, 231, 4745, 1528–1533, 1986Sci...231.1528R, 10.1126/science.11542058, 0036-8075, 11542058, and extinction appears to be the ultimate fate of all species.JOURNAL, Avise, John C., Hubbell, Stephen P., Stephen P. Hubbell, Ayala, Francisco J., August 12, 2008, In the light of evolution II: Biodiversity and extinction, Proc. Natl. Acad. Sci. U.S.A., 105, Suppl. 1, 11453–11457, 2008PNAS..10511453A, 10.1073/pnas.0802504105, 0027-8424, 2556414, 18695213, These extinctions have happened continuously throughout the history of life, although the rate of extinction spikes in occasional mass extinction events.JOURNAL, Raup, David M., July 19, 1994, The role of extinction in evolution, Proc. Natl. Acad. Sci. U.S.A., 91, 15, 6758–6763, 1994PNAS...91.6758R, 10.1073/pnas.91.15.6758, 0027-8424, 44280, 8041694, The Cretaceous–Paleogene extinction event, during which the non-avian dinosaurs became extinct, is the most well-known, but the earlier Permian–Triassic extinction event was even more severe, with approximately 96% of all marine species driven to extinction. The Holocene extinction event is an ongoing mass extinction associated with humanity's expansion across the globe over the past few thousand years. Present-day extinction rates are 100–1000 times greater than the background rate and up to 30% of current species may be extinct by the mid 21st century.JOURNAL, Novacek, Michael J., Cleland, Elsa E., May 8, 2001, The current biodiversity extinction event: scenarios for mitigation and recovery, 10.1073/pnas.091093698, Proc. Natl. Acad. Sci. U.S.A., 98, 10, 5466–5470, 2001PNAS...98.5466N, 0027-8424, 33235, 11344295, Human activities are now the primary cause of the ongoing extinction event;JOURNAL, Pimm, Stuart, Stuart Pimm, Raven, Peter, Peter H. Raven, Peterson, Alan, Şekercioğlu, Çağan H., Ehrlich, Paul R., Paul R. Ehrlich, July 18, 2006, Human impacts on the rates of recent, present and future bird extinctions, Proc. Natl. Acad. Sci. U.S.A., 103, 29, 10941–10946, 2006PNAS..10310941P, 10.1073/pnas.0604181103, 0027-8424, 1544153, 16829570, 3, JOURNAL, Barnosky, Anthony D., Anthony David Barnosky, Koch, Paul L., Feranec, Robert S., Wing, Scott L., Shabel, Alan B., October 1, 2004, Assessing the Causes of Late Pleistocene Extinctions on the Continents, Science, 306, 5693, 70–75, 2004Sci...306...70B, 10.1126/science.1101476, 0036-8075, 15459379, 3,, global warming may further accelerate it in the future.JOURNAL, Lewis, Owen T., January 29, 2006, Climate change, species–area curves and the extinction crisis, Philosophical Transactions of the Royal Society B, 361, 1465, 163–171, 10.1098/rstb.2005.1712, 0962-8436, 1831839, 16553315, Despite the estimated extinction of more than 99 percent of all species that ever lived on Earth,{{harvnb|Stearns|Stearns|1999|p=X}} about 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described.WEB,weblink Researchers find that Earth may be home to 1 trillion species, May 2, 2016, National Science Foundation, Arlington County, Virginia, 2016-05-06, live,weblink 2016-05-04, The role of extinction in evolution is not very well understood and may depend on which type of extinction is considered. The causes of the continuous "low-level" extinction events, which form the majority of extinctions, may be the result of competition between species for limited resources (the competitive exclusion principle). If one species can out-compete another, this could produce species selection, with the fitter species surviving and the other species being driven to extinction. The intermittent mass extinctions are also important, but instead of acting as a selective force, they drastically reduce diversity in a nonspecific manner and promote bursts of rapid evolution and speciation in survivors.JOURNAL, Jablonski, David, May 8, 2001, Lessons from the past: Evolutionary impacts of mass extinctions, Proc. Natl. Acad. Sci. U.S.A., 98, 10, 5393–5398, 2001PNAS...98.5393J, 10.1073/pnas.101092598, 0027-8424, 33224, 11344284, {{Clear}}

Evolutionary history of life

{{align|right|{{Life timeline}}}}{{See also|Timeline of evolutionary history of life}}

Origin of life

{{Further|Abiogenesis|Earliest known life forms|Panspermia|RNA world hypothesis}}The Earth is about 4.54 billion years old.WEB,weblink Age of the Earth, July 9, 2007, United States Geological Survey, 2015-05-31, live,weblink" title="">weblink 2005-12-23, {{harvnb|Dalrymple|2001|pp=205–221}}JOURNAL, Manhesa, Gérard, Allègre, Claude J., Claude Allègre, Dupréa, Bernard, Hamelin, Bruno, May 1980, Lead isotope study of basic-ultrabasic layered complexes: Speculations about the age of the earth and primitive mantle characteristics, Earth and Planetary Science Letters, 47, 3, 370–382, 1980E&PSL..47..370M, 10.1016/0012-821X(80)90024-2, 0012-821X, The earliest undisputed evidence of life on Earth dates from at least 3.5 billion years ago,JOURNAL, Schopf, J. William, J. William Schopf, Kudryavtsev, Anatoliy B., Czaja, Andrew D., Tripathi, Abhishek B., October 5, 2007, Evidence of Archean life: Stromatolites and microfossils, Precambrian Research, 158, 141–155, 3–4, 10.1016/j.precamres.2007.04.009, 0301-9268, 2007PreR..158..141S, {{harvnb|Raven|Johnson|2002|p=68}} during the Eoarchean Era after a geological crust started to solidify following the earlier molten Hadean Eon. Microbial mat fossils have been found in 3.48 billion-year-old sandstone in Western Australia.NEWS, Borenstein, Seth, November 13, 2013, Oldest fossil found: Meet your microbial mom,weblink Excite, Yonkers, New York, Mindspark Interactive Network, Associated Press, 2015-05-31, live,weblink" title="">weblink June 29, 2015, NEWS, Pearlman, Jonathan, November 13, 2013, Oldest signs of life on Earth found,weblink The Daily Telegraph, London, Telegraph Media Group, 2014-12-15, live,weblink" title="">weblink 2014-12-16, JOURNAL, Noffke, Nora, Christian, Daniel, Wacey, David, Hazen, Robert M., Robert Hazen, November 16, 2013, Microbially Induced Sedimentary Structures Recording an Ancient Ecosystem in the ca. 3.48 Billion-Year-Old Dresser Formation, Pilbara, Western Australia, Astrobiology (journal), Astrobiology, 13, 12, 1103–1124, 2013AsBio..13.1103N, 10.1089/ast.2013.1030, 1531-1074, 3870916, 24205812, Other early physical evidence of a biogenic substance is graphite in 3.7 billion-year-old metasedimentary rocks discovered in Western GreenlandJOURNAL, Ohtomo, Yoko, Kakegawa, Takeshi, Ishida, Akizumi, Nagase, Toshiro, Rosing, Minik T., 3, January 2014, Evidence for biogenic graphite in early Archaean Isua metasedimentary rocks, Nature Geoscience, 7, 1, 25–28, 2014NatGe...7...25O, 10.1038/ngeo2025, 1752-0894, as well as "remains of biotic life" found in 4.1 billion-year-old rocks in Western Australia.NEWS, Borenstein, Seth, Hints of life on what was thought to be desolate early Earth,weblink 19 October 2015, Excite, Yonkers, NY, Mindspark Interactive Network, Associated Press, dead,weblink" title="">weblink 23 October 2015, 8 October 2018, JOURNAL, Bell, Elizabeth A., Boehnike, Patrick, Harrison, T. Mark, Mao, Wendy L., November 24, 2015, Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon,weblink Proc. Natl. Acad. Sci. U.S.A., 112, 47, 14518–14521, 10.1073/pnas.1517557112, 0027-8424, 2015-12-30, 26483481, 4664351, 2015PNAS..11214518B, live,weblink" title="">weblink 2015-11-06, Commenting on the Australian findings, Stephen Blair Hedges wrote, "If life arose relatively quickly on Earth, then it could be common in the universe."NEWS, Schouten, Lucy, October 20, 2015, When did life first emerge on Earth? Maybe a lot earlier than we thought,weblink The Christian Science Monitor, Boston, Massachusetts, Christian Science Publishing Society, 0882-7729,weblink" title="">weblink 2016-03-22, live, 2018-07-11, In July 2016, scientists reported identifying a set of 355 genes from the last universal common ancestor (LUCA) of all organisms living on Earth.NEWS, Wade, Nicholas, Nicholas Wade, Meet Luca, the Ancestor of All Living Things,weblink July 25, 2016, The New York Times, New York, The New York Times Company, 0362-4331, 2016-07-25, live,weblink" title="">weblink July 28, 2016, More than 99 percent of all species, amounting to over five billion species,{{harvnb|McKinney|1997|p=110}} that ever lived on Earth are estimated to be extinct.NEWS, Novacek, Michael J., November 8, 2014, Prehistory's Brilliant Future,weblink The New York Times, New York, The New York Times Company, 0362-4331, 2014-12-25, live,weblink" title="">weblink 2014-12-29, Estimates on the number of Earth's current species range from 10 million to 14 million,JOURNAL, Mora, Camilo, Tittensor, Derek P., Adl, Sina, Simpson, Alastair G.B., Worm, Boris, Boris Worm, 3, August 23, 2011, How Many Species Are There on Earth and in the Ocean?, PLOS Biology, 9, 8, e1001127, 10.1371/journal.pbio.1001127, 1545-7885, 3160336, 21886479, {{harvnb|Miller|Spoolman|2012|p=62}} of which about 1.9 million are estimated to have been named{{harvnb|Chapman|2009}} and 1.6 million documented in a central database to date,WEB,weblink Species 2000 & ITIS Catalogue of Life, 2016 Annual Checklist, 2016, Roskov, Y., Abucay, L., Orrell, T., Nicolson, D., Flann, C., Bailly, N., Kirk, P., Bourgoin, T., DeWalt, R.E., Decock, W., De Wever, A., 4, Species 2000, Naturalis Biodiversity Center, Leiden, Netherlands, 2405-884X, 2016-11-06, live,weblink" title="">weblink 2016-11-12, leaving at least 80 percent not yet described.Highly energetic chemistry is thought to have produced a self-replicating molecule around 4 billion years ago, and half a billion years later the last common ancestor of all life existed. The current scientific consensus is that the complex biochemistry that makes up life came from simpler chemical reactions.JOURNAL, Peretó, Juli, March 2005, Controversies on the origin of life,weblink International Microbiology, 8, 1, 23–31, 1139-6709, 15906258, dead,weblink" title="">weblink 2015-08-24, The beginning of life may have included self-replicating molecules such as RNAJOURNAL, Joyce, Gerald F., Gerald Joyce, July 11, 2002, The antiquity of RNA-based evolution, Nature, 418, 6894, 214–221, 2002Natur.418..214J, 10.1038/418214a, 0028-0836, 12110897, and the assembly of simple cells.JOURNAL, Trevors, Jack T., Psenner, Roland, December 2001, From self-assembly of life to present-day bacteria: a possible role for nanocells, FEMS Microbiology Reviews, 25, 5, 573–582, 10.1111/j.1574-6976.2001.tb00592.x, 1574-6976, 11742692,

Common descent

{{Further|Common descent|Evidence of common descent}}All organisms on Earth are descended from a common ancestor or ancestral gene pool.JOURNAL, Theobald, Douglas L., May 13, 2010, A formal test of the theory of universal common ancestry, Nature, 465, 7295, 219–222, 2010Natur.465..219T, 10.1038/nature09014, 0028-0836, 20463738, Current species are a stage in the process of evolution, with their diversity the product of a long series of speciation and extinction events.JOURNAL, Bapteste, Eric, Walsh, David A., June 2005, Does the 'Ring of Life' ring true?, Trends (journals), Trends in Microbiology, 13, 6, 256–261, 10.1016/j.tim.2005.03.012, 0966-842X, 15936656, The common descent of organisms was first deduced from four simple facts about organisms: First, they have geographic distributions that cannot be explained by local adaptation. Second, the diversity of life is not a set of completely unique organisms, but organisms that share morphological similarities. Third, vestigial traits with no clear purpose resemble functional ancestral traits. Fourth, organisms can be classified using these similarities into a hierarchy of nested groups, similar to a family tree.{{harvnb|Darwin|1859|p=1}}File:Ape skeletons.png|upright=1.45|thumb|left|The hominoids are descendants of a common ancestor.]] Modern research has suggested that, due to horizontal gene transfer, this "tree of life" may be more complicated than a simple branching tree since some genes have spread independently between distantly related species.JOURNAL, Doolittle, W. Ford, Bapteste, Eric, February 13, 2007, Pattern pluralism and the Tree of Life hypothesis, Proc. Natl. Acad. Sci. U.S.A., 104, 7, 2043–2049, 2007PNAS..104.2043D, 10.1073/pnas.0610699104, 0027-8424, 1892968, 17261804, JOURNAL, Kunin, Victor, Goldovsky, Leon, Darzentas, Nikos, Ouzounis, Christos A., July 2005, The net of life: Reconstructing the microbial phylogenetic network, Genome Research, 15, 7, 954–959, 10.1101/gr.3666505, 1088-9051, 15965028, 1172039, To solve this problem and others, some authors prefer to use the "Coral of life" as a metaphor or a mathematical model to illustrate the evolution of life. This view dates back to an idea briefly mentioned by Darwin but later abandoned.{{harvnb|Darwin|1837|p=25}}Past species have also left records of their evolutionary history. Fossils, along with the comparative anatomy of present-day organisms, constitute the morphological, or anatomical, record.JOURNAL, Jablonski, David, June 25, 1999, The Future of the Fossil Record, Science, 284, 5423, 2114–2116, 10381868, 10.1126/science.284.5423.2114, 0036-8075, By comparing the anatomies of both modern and extinct species, paleontologists can infer the lineages of those species. However, this approach is most successful for organisms that had hard body parts, such as shells, bones or teeth. Further, as prokaryotes such as bacteria and archaea share a limited set of common morphologies, their fossils do not provide information on their ancestry.More recently, evidence for common descent has come from the study of biochemical similarities between organisms. For example, all living cells use the same basic set of nucleotides and amino acids.JOURNAL, Mason, Stephen F., September 6, 1984, Origins of biomolecular handedness, Nature, 311, 5981, 19–23, 1984Natur.311...19M, 10.1038/311019a0, 0028-0836, 6472461, The development of molecular genetics has revealed the record of evolution left in organisms' genomes: dating when species diverged through the molecular clock produced by mutations.JOURNAL, Wolf, Yuri I., Rogozin, Igor B., Grishin, Nick V., Koonin, Eugene V., Eugene Koonin, September 1, 2002, Genome trees and the tree of life, Trends in Genetics, 18, 9, 472–479, 10.1016/S0168-9525(02)02744-0, 0168-9525, 12175808, For example, these DNA sequence comparisons have revealed that humans and chimpanzees share 98% of their genomes and analysing the few areas where they differ helps shed light on when the common ancestor of these species existed.JOURNAL, Varki, Ajit, Ajit Varki, Altheide, Tasha K., December 2005, Comparing the human and chimpanzee genomes: searching for needles in a haystack, Genome Research, 15, 12, 1746–1758, 10.1101/gr.3737405, 1088-9051, 16339373,,

Evolution of life

{{PhylomapA|size=320px|align=right|caption=Evolutionary tree showing the divergence of modern species from their common ancestor in the centre.JOURNAL, Ciccarelli, Francesca D., Doerks, Tobias, von Mering, Christian, Creevey, Christopher J., Snel, Berend, Bork, Peer, Peer Bork, March 3, 2006, Toward Automatic Reconstruction of a Highly Resolved Tree of Life, Science, 311, 5765, 1283–1287, 2006Sci...311.1283C, 10.1126/science.1123061, 0036-8075, 16513982, 3,weblink live,weblink" title="">weblink 2016-03-04,, The three domains are coloured, with bacteria blue, archaea green and eukaryotes red.}}Prokaryotes inhabited the Earth from approximately 3–4 billion years ago.JOURNAL, Cavalier-Smith, Thomas, Thomas Cavalier-Smith, June 29, 2006, Cell evolution and Earth history: stasis and revolution, Philosophical Transactions of the Royal Society B, 361, 1470, 969–1006, 10.1098/rstb.2006.1842, 0962-8436, 1578732, 16754610, JOURNAL, Schopf, J. William, June 29, 2006, Fossil evidence of Archaean life, Philosophical Transactions of the Royal Society B, 361, 1470, 869–885, 10.1098/rstb.2006.1834, 0962-8436, 1578735, 16754604,
  • JOURNAL, Altermann, Wladyslaw, Kazmierczak, Józef, November 2003, Archean microfossils: a reappraisal of early life on Earth, Research in Microbiology, 154, 9, 611–617, 10.1016/j.resmic.2003.08.006, 0923-2508, 14596897, No obvious changes in morphology or cellular organisation occurred in these organisms over the next few billion years.JOURNAL, Schopf, J. William, July 19, 1994, Disparate rates, differing fates: tempo and mode of evolution changed from the Precambrian to the Phanerozoic, Proc. Natl. Acad. Sci. U.S.A., 91, 15, 6735–6742, 1994PNAS...91.6735S, 10.1073/pnas.91.15.6735, 0027-8424, 44277, 8041691, The eukaryotic cells emerged between 1.6–2.7 billion years ago. The next major change in cell structure came when bacteria were engulfed by eukaryotic cells, in a cooperative association called endosymbiosis.JOURNAL, Poole, Anthony M., Penny, David, January 2007, Evaluating hypotheses for the origin of eukaryotes, BioEssays, 29, 1, 74–84, 10.1002/bies.20516, 0265-9247, 17187354, JOURNAL, Dyall, Sabrina D., Brown, Mark T., Johnson, Patricia J., Patricia J. Johnson, April 9, 2004, Ancient Invasions: From Endosymbionts to Organelles, Science, 304, 5668, 253–257, 2004Sci...304..253D, 10.1126/science.1094884, 0036-8075, 15073369, The engulfed bacteria and the host cell then underwent coevolution, with the bacteria evolving into either mitochondria or hydrogenosomes.JOURNAL, Martin, William, October 2005, The missing link between hydrogenosomes and mitochondria, Trends in Microbiology, 13, 10, 457–459, 10.1016/j.tim.2005.08.005, 0966-842X, 16109488, Another engulfment of cyanobacterial-like organisms led to the formation of chloroplasts in algae and plants.JOURNAL, Lang, B. Franz, Gray, Michael W., Burger, Gertraud, December 1999, Mitochondrial genome evolution and the origin of eukaryotes, Annual Review of Genetics, 33, 351–397, 10.1146/annurev.genet.33.1.351, 0066-4197, 10690412,
  • JOURNAL, McFadden, Geoffrey Ian, December 1, 1999, Endosymbiosis and evolution of the plant cell, Current Opinion in Plant Biology, 2, 6, 513–519, 10.1016/S1369-5266(99)00025-4, 1369-5266, 10607659,
The history of life was that of the unicellular eukaryotes, prokaryotes and archaea until about 610 million years ago when multicellular organisms began to appear in the oceans in the Ediacaran period.JOURNAL, DeLong, Edward F., Edward DeLong, Pace, Norman R., Norman R. Pace, August 1, 2001, Environmental Diversity of Bacteria and Archaea, Systematic Biology, 50, 4, 470–478, 10.1080/106351501750435040, 1063-5157, 12116647,weblink live,weblink" title="">weblink 2016-02-22,, The evolution of multicellularity occurred in multiple independent events, in organisms as diverse as sponges, brown algae, cyanobacteria, slime moulds and myxobacteria.JOURNAL, Kaiser, Dale, A. Dale Kaiser, December 2001, Building a multicellular organism, Annual Review of Genetics, 35, 103–123, 10.1146/annurev.genet.35.102401.090145, 0066-4197, 11700279, In January 2016, scientists reported that, about 800 million years ago, a minor genetic change in a single molecule called GK-PID may have allowed organisms to go from a single cell organism to one of many cells.NEWS, Zimmer, Carl, Carl Zimmer, Genetic Flip Helped Organisms Go From One Cell to Many,weblink January 7, 2016, The New York Times, New York, The New York Times Company, 0362-4331, 2016-01-07, live,weblink" title="">weblink 2016-01-07, Soon after the emergence of these first multicellular organisms, a remarkable amount of biological diversity appeared over approximately 10 million years, in an event called the Cambrian explosion. Here, the majority of types of modern animals appeared in the fossil record, as well as unique lineages that subsequently became extinct.JOURNAL, Valentine, James W., James W. Valentine, Jablonski, David, Erwin, Douglas H., Douglas Erwin, March 1, 1999, Fossils, molecules and embryos: new perspectives on the Cambrian explosion,weblink Development (journal), Development, 126, 5, 851–859, 0950-1991, 9927587, 2014-12-30, live,weblink" title="">weblink 2015-03-01, Various triggers for the Cambrian explosion have been proposed, including the accumulation of oxygen in the atmosphere from photosynthesis.JOURNAL, Ohno, Susumu, January 1997, The reason for as well as the consequence of the Cambrian explosion in animal evolution, Journal of Molecular Evolution, 44, Suppl. 1, S23–S27, 10.1007/PL00000055, 0022-2844, 9071008, 1997JMolE..44S..23O,
  • JOURNAL, Valentine, James W., Jablonski, David, Morphological and developmental macroevolution: a paleontological perspective,weblink 2003, The International Journal of Developmental Biology, 47, 7–8, 517–522, 0214-6282, 14756327, 2014-12-30, live,weblink" title="">weblink 2014-10-24,
About 500 million years ago, plants and fungi colonised the land and were soon followed by arthropods and other animals.JOURNAL, Waters, Elizabeth R., December 2003, Molecular adaptation and the origin of land plants, Molecular Phylogenetics and Evolution, 29, 3, 456–463, 10.1016/j.ympev.2003.07.018, 1055-7903, 14615186, Insects were particularly successful and even today make up the majority of animal species.JOURNAL, Mayhew, Peter J., Peter Mayhew (biologist), August 2007, Why are there so many insect species? Perspectives from fossils and phylogenies, Biological Reviews, 82, 3, 425–454, 10.1111/j.1469-185X.2007.00018.x, 1464-7931, 17624962, Amphibians first appeared around 364 million years ago, followed by early amniotes and birds around 155 million years ago (both from "reptile"-like lineages), mammals around 129 million years ago, homininae around 10 million years ago and modern humans around 250,000 years ago.JOURNAL, Carroll, Robert L., Robert L. Carroll, May 2007, The Palaeozoic Ancestry of Salamanders, Frogs and Caecilians, Zoological Journal of the Linnean Society, 150, Supplement s1, 1–140, 10.1111/j.1096-3642.2007.00246.x, 1096-3642, JOURNAL, Wible, John R., Rougier, Guillermo W., Novacek, Michael J., Asher, Robert J., June 21, 2007, Cretaceous eutherians and Laurasian origin for placental mammals near the K/T boundary, Nature, 447, 7147, 1003–1006, 2007Natur.447.1003W, 10.1038/nature05854, 0028-0836, 17581585, JOURNAL, Witmer, Lawrence M., Lawrence Witmer, July 28, 2011, Palaeontology: An icon knocked from its perch, Nature, 475, 7357, 458–459, 10.1038/475458a, 0028-0836, 21796198, However, despite the evolution of these large animals, smaller organisms similar to the types that evolved early in this process continue to be highly successful and dominate the Earth, with the majority of both biomass and species being prokaryotes.


Concepts and models used in evolutionary biology, such as natural selection, have many applications.JOURNAL, Bull, James J., James J. Bull, Wichman, Holly A., November 2001, Applied evolution, Annual Review of Ecology and Systematics, 32, 183–217, 10.1146/annurev.ecolsys.32.081501.114020, 1545-2069, Artificial selection is the intentional selection of traits in a population of organisms. This has been used for thousands of years in the domestication of plants and animals.JOURNAL, Doebley, John F., Gaut, Brandon S., Smith, Bruce D., Bruce D. Smith, December 29, 2006, The Molecular Genetics of Crop Domestication, Cell, 127, 7, 1309–1321, 10.1016/j.cell.2006.12.006, 0092-8674, 17190597, More recently, such selection has become a vital part of genetic engineering, with selectable markers such as antibiotic resistance genes being used to manipulate DNA. Proteins with valuable properties have evolved by repeated rounds of mutation and selection (for example modified enzymes and new antibodies) in a process called directed evolution.JOURNAL, Jäckel, Christian, Kast, Peter, Hilvert, Donald, June 2008, Protein Design by Directed Evolution, Annual Review of Biophysics, 37, 153–173, 10.1146/annurev.biophys.37.032807.125832, 1936-122X, 18573077, Understanding the changes that have occurred during an organism's evolution can reveal the genes needed to construct parts of the body, genes which may be involved in human genetic disorders.JOURNAL, Maher, Brendan, April 8, 2009, Evolution: Biology's next top model?, Nature, 458, 7239, 695–698, 10.1038/458695a, 0028-0836, 19360058, For example, the Mexican tetra is an albino cavefish that lost its eyesight during evolution. Breeding together different populations of this blind fish produced some offspring with functional eyes, since different mutations had occurred in the isolated populations that had evolved in different caves.JOURNAL, Borowsky, Richard, January 8, 2008, Restoring sight in blind cavefish, Current Biology, 18, 1, R23–R24, 10.1016/j.cub.2007.11.023, 0960-9822, 18177707, 1996CBio....6.1213A, This helped identify genes required for vision and pigmentation.JOURNAL, Gross, Joshua B., Borowsky, Richard, Tabin, Clifford J., January 2, 2009, Barsh, Gregory S., A novel role for Mc1r in the parallel evolution of depigmentation in independent populations of the cavefish Astyanax mexicanus, PLOS Genetics, 5, 1, e1000326, 10.1371/journal.pgen.1000326, 1553-7390, 2603666, 19119422, Evolutionary theory has many applications in medicine. Many human diseases are not static phenomena, but capable of evolution. Viruses, bacteria, fungi and cancers evolve to be resistant to host immune defences, as well as pharmaceutical drugs.JOURNAL, Merlo, Lauren M.F., Pepper, John W., Reid, Brian J., Maley, Carlo C., Carlo Maley, December 2006, Cancer as an evolutionary and ecological process, Nature Reviews Cancer, 6, 12, 924–935, 10.1038/nrc2013, 1474-175X, 17109012, JOURNAL, Pan, Dabo, Weiwei Xue, Wenqi Zhang, Huanxiang Liu, Xiaojun Yao, October 2012, Understanding the drug resistance mechanism of hepatitis C virus NS3/4A to ITMN-191 due to R155K, A156V, D168A/E mutations: a computational study, Biochimica et Biophysica Acta, Biochimica et Biophysica Acta (BBA) - General Subjects, 1820, 10, 1526–1534, 10.1016/j.bbagen.2012.06.001, 0304-4165, 22698669, 3, JOURNAL, Woodford, Neil, Ellington, Matthew J., January 2007, The emergence of antibiotic resistance by mutation., Clinical Microbiology and Infection, 13, 1, 5–18, 10.1111/j.1469-0691.2006.01492.x, 1198-743X, 17184282, These same problems occur in agriculture with pesticideJOURNAL, Labbé, Pierrick, Berticat, Claire, Berthomieu, Arnaud, Unal, Sandra, Bernard, Clothilde, Weill, Mylène, Lenormand, Thomas, November 16, 2007, Forty Years of Erratic Insecticide Resistance Evolution in the Mosquito Culex pipiens, PLOS Genetics, 3, 11, e205, 10.1371/journal.pgen.0030205, 1553-7390, 18020711, 3, 2077897, and herbicideJOURNAL, Neve, Paul, October 2007, Challenges for herbicide resistance evolution and management: 50 years after Harper, Weed Research, 47, 5, 365–369, 10.1111/j.1365-3180.2007.00581.x, 0043-1737, resistance. It is possible that we are facing the end of the effective life of most of available antibioticsJOURNAL, Rodríguez-Rojas, Alexandro, Rodríguez-Beltrán, Jerónimo, Couce, Alejandro, Blázquez, Jesús, August 2013, Antibiotics and antibiotic resistance: A bitter fight against evolution, International Journal of Medical Microbiology, 303, 6–7, 293–297, 10.1016/j.ijmm.2013.02.004, 1438-4221, 23517688,weblink and predicting the evolution and evolvabilityJOURNAL, Schenk, Martijn F., Szendro, Ivan G., Krug, Joachim, de Visser, J. Arjan G.M., June 28, 2012, Quantifying the Adaptive Potential of an Antibiotic Resistance Enzyme, PLOS Genetics, 8, 6, e1002783, 10.1371/journal.pgen.1002783, 1553-7390, 22761587, 3386231, of our pathogens and devising strategies to slow or circumvent it is requiring deeper knowledge of the complex forces driving evolution at the molecular level.JOURNAL, Read, Andrew F., Lynch, Penelope A., Thomas, Matthew B., April 7, 2009, How to Make Evolution-Proof Insecticides for Malaria Control, PLOS Biology, 7, 4, e1000058, 10.1371/journal.pbio.1000058, 1545-7885, 19355786, 3279047, In computer science, simulations of evolution using evolutionary algorithms and artificial life started in the 1960s and were extended with simulation of artificial selection.JOURNAL, Fraser, Alex S., Alex Fraser (scientist), January 18, 1958, Monte Carlo Analyses of Genetic Models, Nature, 181, 4603, 208–209, 1958Natur.181..208F, 10.1038/181208a0, 0028-0836, 13504138, Artificial evolution became a widely recognised optimisation method as a result of the work of Ingo Rechenberg in the 1960s. He used evolution strategies to solve complex engineering problems.{{harvnb|Rechenberg|1973}} Genetic algorithms in particular became popular through the writing of John Henry Holland.{{harvnb|Holland|1975}} Practical applications also include automatic evolution of computer programmes.{{harvnb|Koza|1992}} Evolutionary algorithms are now used to solve multi-dimensional problems more efficiently than software produced by human designers and also to optimise the design of systems.JOURNAL, Jamshidi, Mo, August 15, 2003, Tools for intelligent control: fuzzy controllers, neural networks and genetic algorithms, Philosophical Transactions of the Royal Society A, 361, 1809, 1781–1808, 2003RSPTA.361.1781J, 10.1098/rsta.2003.1225, 1364-503X, 12952685,

Social and cultural responses

{{Further|Social effects of evolutionary theory|1860 Oxford evolution debate|Creation–evolution controversy|Objections to evolution|Evolution in fiction}}File:Editorial cartoon depicting Charles Darwin as an ape (1871).jpg|upright|thumb|As evolution became widely accepted in the 1870s, caricatures of Charles Darwin with an ape or Browne|2003|pp=376–379}}In the 19th century, particularly after the publication of On the Origin of Species in 1859, the idea that life had evolved was an active source of academic debate centred on the philosophical, social and religious implications of evolution. Today, the modern evolutionary synthesis is accepted by a vast majority of scientists. However, evolution remains a contentious concept for some theists.For an overview of the philosophical, religious and cosmological controversies, see:
  • {{harvnb|Dennett|1995}}
For the scientific and social reception of evolution in the 19th and early 20th centuries, see:
  • BOOK, Johnston, Ian C., Ian C. Johnston, 1999, Section Three: The Origins of Evolutionary Theory,weblink ... And Still We Evolve: A Handbook for the Early History of Modern Science,weblink 3rd revised, Nanaimo, BC, Liberal Studies Department, Vancouver Island University, Malaspina University-College, 2015-01-01, live,weblink" title="">weblink 2016-04-16,
  • {{harvnb|Bowler|2003}}
  • JOURNAL, Zuckerkandl, Emile, Emile Zuckerkandl, December 30, 2006, Intelligent design and biological complexity, Gene (journal), Gene, 385, 2–18, 17011142, 10.1016/j.gene.2006.03.025, 0378-1119,
While various religions and denominations have reconciled their beliefs with evolution through concepts such as theistic evolution, there are creationists who believe that evolution is contradicted by the creation myths found in their religions and who raise various objections to evolution.JOURNAL, Ross, Marcus R., Marcus R. Ross, May 2005, Who Believes What? Clearing up Confusion over Intelligent Design and Young-Earth Creationism,weblink Journal of Geoscience Education, 53, 3, 319–323, 1089-9995, 2008-04-28, 2005JGeEd..53..319R, 10.5408/1089-9995-53.3.319, live,weblink" title="">weblink 2008-05-11,, JOURNAL, Hameed, Salman, December 12, 2008, Bracing for Islamic Creationism,weblink Science, 322, 5908, 1637–1638, 10.1126/science.1163672, 0036-8075, 19074331, dead,weblink" title="">weblink 2014-11-10, As had been demonstrated by responses to the publication of Vestiges of the Natural History of Creation in 1844, the most controversial aspect of evolutionary biology is the implication of human evolution that humans share common ancestry with apes and that the mental and moral faculties of humanity have the same types of natural causes as other inherited traits in animals.{{harvnb|Bowler|2003}} In some countries, notably the United States, these tensions between science and religion have fuelled the current creation–evolution controversy, a religious conflict focusing on politics and public education.JOURNAL, Miller, Jon D., Scott, Eugenie C., Okamoto, Shinji, August 11, 2006, Public Acceptance of Evolution, Science, 313, 5788, 765–766, 10.1126/science.1126746, 0036-8075, 16902112, While other scientific fields such as cosmologyJOURNAL, Spergel, David Nathaniel, David Spergel, Verde, Licia, Peiris, Hiranya V., Komatsu, Eiichiro, Nolta, Michael R., Bennett, Charles L., Charles L. Bennett, Halpern, Mark, Hinshaw, Gary, Jarosik, Norman, 2003, First-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Determination of Cosmological Parameters, The Astrophysical Journal, The Astrophysical Journal Supplement Series, 148, 1, 175–194, astro-ph/0302209, 2003ApJS..148..175S, 10.1086/377226, 3, and Earth scienceJOURNAL, Wilde, Simon A., Valley, John W., Peck, William H., Graham, Colin M., January 11, 2001, Evidence from detrital zircons for the existence of continental crust and oceans on the Earth 4.4 Gyr ago, Nature, 409, 6817, 175–178, 10.1038/35051550, 0028-0836, 11196637, also conflict with literal interpretations of many religious texts, evolutionary biology experiences significantly more opposition from religious literalists.The teaching of evolution in American secondary school biology classes was uncommon in most of the first half of the 20th century. The Scopes Trial decision of 1925 caused the subject to become very rare in American secondary biology textbooks for a generation, but it was gradually re-introduced later and became legally protected with the 1968 Epperson v. Arkansas decision. Since then, the competing religious belief of creationism was legally disallowed in secondary school curricula in various decisions in the 1970s and 1980s, but it returned in pseudoscientific form as intelligent design (ID), to be excluded once again in the 2005 Kitzmiller v. Dover Area School District case.JOURNAL, Branch, Glenn, Glenn Branch, March 2007, Understanding Creationism after Kitzmiller, BioScience, 57, 3, 278–284, 10.1641/B570313, 0006-3568, 1985BioSc..35..499W, The debate over Darwin's ideas did not generate significant controversy in China.JOURNAL, Xiaoxing Jin, March 2019, Translation and transmutation: the Origin of Species in China, The British Journal for the History of Science, Cambridge, Cambridge University Press on behalf of The British Society for the History of Science, 52, 1, 117–141, 30587253, 10.1017/S0007087418000808,

See also

{{Wikipedia books|Evolution}}{{div col|colwidth=30em}} {{div col end}}




  • BOOK, Altenberg, Lee, Lee Altenberg, 1995, Genome growth and the evolution of the genotype-phenotype map, Banzhaf, Wolfgang, Eeckman, Frank H., Evolution and Biocomputation: Computational Models of Evolution, Lecture Notes in Computer Science, 899, 205–259, Berlin; New York, Springer Science+Business Media, Springer-Verlag Berlin Heidelberg, 10.1007/3-540-59046-3_11, 0302-9743, 978-3-540-59046-0, 95005970, 32049812, harv,,
  • BOOK, Ayala, Francisco J., Francisco J. Ayala, Avise, John C., John Avise, 2014, Essential Readings in Evolutionary Biology, Baltimore, Maryland, Johns Hopkins University Press, 978-1-4214-1305-1, 2013027718, 854285705, harv,
  • BOOK, Birdsell, John A., Wills, Christopher, Christopher Wills, 2003, The Evolutionary Origin and Maintenance of Sexual Recombination: A Review of Contemporary Models, MacIntyre, Ross J., Clegg, Michael T., Evolutionary Biology, Evolutionary Biology, 33, New York, Springer Science+Business Media, 978-1-4419-3385-0, 0071-3260, 751583918, harv,
  • BOOK, Bowler, Peter J., Peter J. Bowler, 1989, The Mendelian Revolution: The Emergence of Hereditarian Concepts in Modern Science and Society, Baltimore, Maryland, Johns Hopkins University Press, 978-0-8018-3888-0, 89030914, 19322402, harv,
  • BOOK, Bowler, Peter J., Peter J. Bowler, 2003, Evolution: The History of an Idea, 3rd completely rev. and expanded, Berkeley, California, University of California Press, 978-0-520-23693-6, 2002007569, 49824702, harv,
  • BOOK, Browne, Janet, Janet Browne, 2003, Charles Darwin: The Power of Place, 2, London, Random House, Pimlico, 978-0-7126-6837-8, 94006598, 52327000, harv,
  • BOOK, Burkhardt, Frederick, Frederick Burkhardt, Smith, Sydney, 1991, The Correspondence of Charles Darwin, The Correspondence of Charles Darwin, 7: 1858–1859, Cambridge, Cambridge University Press, 978-0-521-38564-0, 84045347, 185662993, harv,
  • BOOK, Carroll, Sean B., Sean B. Carroll, Grenier, Jennifer K., Weatherbee, Scott D., 2005, From DNA to Diversity: Molecular Genetics and the Evolution of Animal Design, 2nd, Malden, Massachusetts, Wiley-Blackwell, Blackwell Publishing, 978-1-4051-1950-4, 2003027991, 53972564, harv,
  • BOOK, Chapman, Arthur D., 2009, Numbers of Living Species in Australia and the World, 2nd,weblink 2016-11-06, live,weblink" title="">weblink 2016-12-25, Canberra, Department of the Environment, Water, Heritage and the Arts: Australian Biological Resources Study, 978-0-642-56860-1, 780539206, harv,
  • BOOK, Coyne, Jerry A., Jerry Coyne, 2009, Why Evolution is True, New York, Viking Press, Viking, 978-0-670-02053-9, 2008033973, 233549529, harv,weblink
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  • BOOK, Dawkins, Richard, Richard Dawkins, 1990, The Blind Watchmaker, Penguin Science, London, Penguin Books, 978-0-14-014481-9, 60143870, harv, The Blind Watchmaker,
  • BOOK, Dennett, Daniel, Daniel Dennett, 1995, Darwin's Dangerous Idea: Evolution and the Meanings of Life, New York, Simon & Schuster, 978-0-684-80290-9, 94049158, 31867409, harv, Darwin's Dangerous Idea,
  • BOOK, Dobzhansky, Theodosius, Theodosius Dobzhansky, 1968, On Some Fundamental Concepts of Darwinian Biology, Dobzhansky, Theodosius, Hecht, Max K., Steere, William C., Evolutionary Biology. Volume 2, 1–34, 1st, New York, Appleton-Century-Crofts, 10.1007/978-1-4684-8094-8_1, 24875357, harv, 978-1-4684-8096-2,
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  • BOOK, Moore, Randy, Decker, Mark, Cotner, Sehoya, 2010, Chronology of the Evolution-Creationism Controversy, Santa Barbara, California, Greenwood Publishing Group, Greenwood Press/ABC-CLIO, 978-0-313-36287-3, 2009039784, 422757410, harv,weblink
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  • BOOK, Odum, Eugene P., Eugene Odum, 1971, Fundamentals of Ecology,weblink registration, 3rd, Philadelphia, Pennsylvania, Saunders (imprint), Saunders, 978-0-7216-6941-0, 76081826, 154846, harv,
  • BOOK, Okasha, Samir, 2006, Evolution and the Levels of Selection, Oxford; New York, Oxford University Press, 978-0-19-926797-2, 2006039679, 70985413, harv,
  • BOOK, Panno, Joseph, The Cell: Evolution of the First Organism, 2005, Facts on File science library, New York, Infobase Publishing, Facts on File, 978-0-8160-4946-2, 2003025841, 53901436, harv,
  • BOOK, Piatigorsky, Joram, Kantorow, Marc, Gopal-Srivastava, Rashmi, Tomarev, Stanislav I., 1994, Recruitment of enzymes and stress proteins as lens crystallins, Jansson, Bengt, Jörnvall, Hans, Rydberg, Ulf, Terenius, Lars, Vallee, Bert L., 3, Toward a Molecular Basis of Alcohol Use and Abuse, Exs, Experientia, 71, 241–50, Basel; Boston, Birkhäuser, Birkhäuser Verlag, 10.1007/978-3-0348-7330-7_24, 978-3-7643-2940-2, 94010167, 30030941, 8032155, harv,
  • BOOK, Pigliucci, Massimo, Massimo Pigliucci, Müller, Gerd B., Gerd B. Müller, 2010, Evolution, the Extended Synthesis,weblink live,weblink" title="">weblink 2015-09-18, Cambridge, Massachusetts, MIT Press, 978-0-262-51367-8, 2009024587, 804875316, harv,
  • BOOK, Pocheville, Arnaud, Danchin, Étienne, 2017, Chapter 3: Genetic assimilation and the paradox of blind variation,weblink Huneman, Philippe, Walsh, Denis M., Challenging the Modern Synthesis, New York, Oxford University Press, 978-0-19-937717-6, 2017448929, 1001337947, harv,
  • BOOK, Provine, William B., Will Provine, 1971, The Origins of Theoretical Population Genetics,weblink registration, Chicago History of Science and Medicine, 2nd, Chicago, Illinois, University of Chicago Press, 978-0-226-68464-2, 2001027561, 46660910, harv,
  • BOOK, Provine, William B., 1988, Progress in Evolution and Meaning in Life, Nitecki, Matthew H., Evolutionary Progress, Chicago, Illinois, University of Chicago Press, 978-0-226-58693-9, 88020835, 18380658, harv, "This book is the result of the Spring Systematics Symposium held in May, 1987, at the Field Museum in Chicago"
  • BOOK, Quammen, David, David Quammen, 2006, The Reluctant Mr. Darwin: An Intimate Portrait of Charles Darwin and the Making of His Theory of Evolution, Great Discoveries, 1st, New York, Atlas Books/W.W. Norton & Company, 978-0-393-05981-6, 2006009864, 65400177, harv,weblink
  • BOOK, Raven, Peter H., Peter H. Raven, Johnson, George B., George B. Johnson, 2002, Biology,weblink registration, 6th, Boston, Massachusetts, McGraw-Hill Education, McGraw-Hill, 978-0-07-112261-0, 2001030052, 45806501, harv,
  • BOOK, Ray, John, John Ray, 1686, Historia Plantarum, History of Plants, I, Londini, Typis Mariæ Clark, agr11000774, 2126030, harv,
  • BOOK, Rechenberg, Ingo, Ingo Rechenberg, 1973, Evolutionsstrategie; Optimierung technischer Systeme nach Prinzipien der biologischen Evolution, PhD thesis, Problemata, German, 15, Afterword by Manfred Eigen, Stuttgart-Bad Cannstatt, Frommann-Holzboog, 978-3-7728-0373-4, 74320689, 9020616, harv,
  • BOOK, Ridley, Matt, Matt Ridley, 1993, The Red Queen: Sex and the Evolution of Human Nature, New York, Viking, 978-0-670-84357-2, 636657988, harv, The Red Queen: Sex and the Evolution of Human Nature,
  • BOOK, Stearns, Beverly Peterson, Stearns, Stephen C., Stephen C. Stearns, 1999, Watching, from the Edge of Extinction,weblink registration, New Haven, Connecticut, Yale University Press, 978-0-300-08469-6, 98034087, 803522914, harv,
  • BOOK, Stevens, Anthony, Anthony Stevens (Jungian analyst), 1982, Archetype: A Natural History of the Self, London, Routledge, Routledge & Kegan Paul, 978-0-7100-0980-7, 84672250, 10458367, harv,
  • BOOK, Voet, Donald, Donald Voet, Voet, Judith G., Judith G. Voet, Pratt, Charlotte W., Charlotte W. Pratt, 2016, Fundamentals of Biochemistry: Life at the Molecular Level, Fifth, Hoboken, New Jersey, Wiley (publisher), John Wiley & Sons, 978-1-11-891840-1, 2016002847, 939245154, harv,
  • BOOK, West-Eberhard, Mary Jane, Mary Jane West-Eberhard, 2003, Developmental Plasticity and Evolution, Oxford; New York, Oxford University Press, 978-0-19-512235-0, 2001055164, 48398911, harv,
  • BOOK, Wiley, E. O., Edward O. Wiley, Lieberman, Bruce S., 2011, Phylogenetics: Theory and Practice of Phylogenetic Systematics, 2nd, Hoboken, New Jersey, Wiley-Blackwell, 978-0-470-90596-8, 2010044283, 741259265, 10.1002/9781118017883, harv,
  • BOOK, Wright, Sewall, Sewall Wright, 1984, Genetic and Biometric Foundations, Evolution and the Genetics of Populations, 1, Chicago, Illinois, University of Chicago Press, 978-0-226-91038-3, 67025533, 246124737, harv,

Further reading

{{further|Bibliography of biology}}{hide}Library resources box
|lcheading=Evolution (Biology)
Introductory reading
  • BOOK, Barrett, Paul H., Weinshank, Donald J., Gottleber, Timothy T., 1981, A Concordance to Darwin's Origin of Species, First Edition, Ithaca, New York, Cornell University Press, 978-0-8014-1319-3, 80066893, 610057960,
  • BOOK, Carroll, Sean B., 2005, Endless Forms Most Beautiful: The New Science of Evo Devo and the Making of the Animal Kingdom, illustrations by Jamie W. Carroll, Josh P. Klaiss, Leanne M. Olds, 1st, New York, W.W. Norton & Company, 978-0-393-06016-4, 2004029388, 57316841,weblink
  • BOOK, Charlesworth, Brian, Brian Charlesworth, Charlesworth, Deborah, Deborah Charlesworth, 2003, Evolution: A Very Short Introduction, Very Short Introductions, Oxford; New York, Oxford University Press, 978-0-19-280251-4, 2003272247, 51668497,
  • BOOK, Gould, Stephen Jay, 1989, Wonderful Life: The Burgess Shale and the Nature of History, 1st, New York, W.W. Norton & Company, 978-0-393-02705-1, 88037469, 18983518, Wonderful Life (book),
  • BOOK, Jones, Steve, Steve Jones (biologist), 1999, Almost Like a Whale: The Origin of Species Updated, London; New York, Doubleday (publisher), Doubleday, 978-0-385-40985-8, 2002391059, 41420544, Almost Like a Whale,
    • BOOK, Jones, Steve, 2000, Darwin's Ghost: The Origin of Species Updated,weblink registration, 1st, New York, Random House, 978-0-375-50103-6, 99053246, 42690131, 2, American version.
  • BOOK, Mader, Sylvia S., Biology, 2007, Significant contributions by Murray P. Pendarvis, 9th, Boston, Massachusetts, McGraw-Hill Education, McGraw-Hill Higher Education, 978-0-07-246463-4, 2005027781, 61748307,
  • BOOK, Maynard Smith, John, 1993, The Theory of Evolution, Canto, Cambridge; New York, Cambridge University Press, 978-0-521-45128-4, 93020358, 27676642, The Theory of Evolution,
  • BOOK, Pallen, Mark J., 2009, The Rough Guide to Evolution, Rough Guides Reference Guides, London; New York, Rough Guides, 978-1-85828-946-5, 2009288090, 233547316,
Advanced reading
  • BOOK, Barton, Nicholas H., Nick Barton, Briggs, Derek E.G., Derek Briggs, Eisen, Jonathan A., Jonathan Eisen, Goldstein, David B., Patel, Nipan H., 2007, Evolution, Cold Spring Harbor, New York, Cold Spring Harbor Laboratory Press, 978-0-87969-684-9, 2007010767, 86090399, 3,
  • BOOK, Coyne, Jerry A., Orr, H. Allen, H. Allen Orr, 2004, Speciation, Sunderland, Massachusetts, Sinauer Associates, 978-0-87893-089-0, 2004009505, 55078441,
  • BOOK, Bergstrom, Carl T., Carl Bergstrom, Dugatkin, Lee Alan, 2012, Evolution, 1st, New York, W.W. Norton & Company, 978-0-393-91341-5, 2011036572, 729341924,
  • BOOK, Gould, Stephen Jay, 2002, The Structure of Evolutionary Theory, Cambridge, Massachusetts, Belknap Press of Harvard University Press, 978-0-674-00613-3, 2001043556, 47869352,weblink
  • BOOK, Hall, Brian K., Olson, Wendy, 2003, Keywords and Concepts in Evolutionary Developmental Biology, Cambridge, Massachusetts, Harvard University Press, 978-0-674-00904-2, 2002192201, 50761342,
  • BOOK, Kauffman, Stuart A., Stuart Kauffman, 1993, The Origins of Order: Self-organization and Selection in Evolution,weblink New York; Oxford, Oxford University Press, 978-0-19-507951-7, 91011148, 895048122,
  • BOOK, Maynard Smith, John, Szathmáry, Eörs, Eörs Szathmáry, 1995, The Major Transitions in Evolution, Oxford; New York, W.H. Freeman Spektrum, 978-0-7167-4525-9, 94026965, 30894392, The Major Transitions in Evolution,
  • BOOK, Mayr, Ernst, 2001, What Evolution Is,weblink registration, New York, Basic Books, 978-0-465-04426-9, 2001036562, 47443814,
  • BOOK, Minelli, Alessandro, Alessandro Minelli, 2009, Forms of Becoming: The Evolutionary Biology of Development, Translation by Mark Epstein, Princeton, New Jersey; Oxford, Princeton University Press, 978-0-691-13568-7, 2008028825, 233030259,

External links

{{Spoken Wikipedia|Evolution.ogg|2005-04-18}} {{Sister project links|evolution|voy=no}}
General information

Experiments concerning the process of biological evolution

Online lectures
{{Evolution|state=uncollapsed}}{{Big History}}{{Breakthrough of the Year}}{{Featured article}}{{Authority control}}

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