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The genetic theory of adaptation: a brief history

Nature Reviews Genetics volume 6, pages 119–127 (2005)Cite this article

Key Points

  • Early evolutionists believed that the genetic basis of adaptation was micromutational.

  • This view was supported by Ronald Fisher's classical mathematical analysis (of 1930) of his 'geometric model' of adaptation.

  • Beginning in the 1980s, studies of quantitative trait loci and microbial experimental evolution revealed that adaptation sometimes involves a modest number of genes, some of which have surprisingly large effects. These experimental findings pose a serious challenge to evolutionary theory.

  • So far, phenotype-based and DNA sequence-based models of adaptation have yielded surprisingly similar results, indicating the possibility of a robust theory of adaptation.

  • Phenotypic models of adaptation show that the genes that cause adaptation should have approximately exponentially distributed effects; that is, involve many genes that have small effect and a few genes that have large effect.

  • DNA sequence models of adaptation indicate that adaptation should involve mutations of relatively large fitness effects and that adaptation is characterized by a pattern of diminishing returns, in which early substitutions have large fitness effects and later ones have smaller effects.

  • Current theories of adaptation adequately explain certain qualitative patterns that characterize genetic data on adaptation; however, it is not yet clear if these theories can explain these data quantitatively.

Abstract

Theoretical studies of adaptation have exploded over the past decade. This work has been inspired by recent, surprising findings in the experimental study of adaptation. For example, morphological evolution sometimes involves a modest number of genetic changes, with some individual changes having a large effect on the phenotype or fitness. Here I survey the history of adaptation theory, focusing on the rise and fall of various views over the past century and the reasons for the slow development of a mature theory of adaptation. I also discuss the challenges that face contemporary theories of adaptation.

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Figure 1: Adaptation in Fisher's geometric model.
Figure 2: A fitness landscape.
Figure 3: The distribution of fitnesses at a locus.

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References

  1. Fisher, R. A. The Genetical Theory of Natural Selection (Oxford Univ. Press, Oxford, 1930). One of the founding documents of modern evolutionary biology. It includes Fisher's classical discussions of his geometric model of adaptation.

    Book  Google Scholar 

  2. Darwin, C. R. The Origin of Species (J. Murray, London, 1859).

    Google Scholar 

  3. Mayr, E. The Growth of Biological Thought (Harvard Univ. Press, Cambridge, Massachusetts, 1982).

    Google Scholar 

  4. Maynard Smith, J. (ed.) Evolution Now: a Century After Darwin (W. H. Freeman and Co., San Francisco, 1982).

    Google Scholar 

  5. Pearson, K. Mathematical contributions to the theory of evolution: on the law of ancestral heredity. Proc. R. Soc. Lond. 62, 386–412 (1898).

    Google Scholar 

  6. Weldon, W. F. R. Attempt to measure the death-rate due to the selective destruction of Carcinus moenas with respect to a particular dimension. Proc. R. Soc. Lond. 58, 360–379 (1895).

    Google Scholar 

  7. Provine, W. B. The Origins of Theoretical Population Genetics (Univ. Chicago Press, Chicago, 1971).

    Google Scholar 

  8. Morgan, T. H. Evolution and Adaptation (Macmillan, New York, 1903).

    Google Scholar 

  9. Bateson, W. Mendel's Principles of Genetics (Cambridge Univ. Press, Cambridge, 1913).

    Google Scholar 

  10. Punnett, R. C. Mimicry in Butterflies (Cambridge Univ. Press, Cambridge, 1915).

    Google Scholar 

  11. Turner, J. R. G. Fisher's evolutionary faith and the challenge of mimicry. Oxford Surv. Evol. Biol. 2, 159–196 (1985).

    Google Scholar 

  12. Bateson, W. in Darwin and Modern Science (ed. Seward, A. C.) 85–101 (Cambridge Univ. Press, Cambridge, 1909).

    Google Scholar 

  13. Fisher, R. A. The correlations between relatives on the supposition of Mendelian inheritance. Trans. R. Soc. Edinb. 52, 399–433 (1918).

    Google Scholar 

  14. Bulmer, M. G. The Mathematical Theory of Quantitative Genetics (Oxford Univ. Press, Oxford, 1980).

    Google Scholar 

  15. Barton, N. H. & Turelli, M. Evolutionary quantitative genetics: how little do we know? Annu. Rev. Genetics 23, 337–370 (1989).

    CAS  Google Scholar 

  16. Turner, J. R. G. in The Probabilistic Revolution Vol. 2 (eds. Kruger, L., Gigerenzer, G. & Morgan, M. S.) 313–354 (The MIT Press, Cambridge, Massachusetts, 1987).

    Google Scholar 

  17. Dobzhansky, T. Genetics and the Origin of Species (Columbia Univ. Press, New York, 1937).

    Google Scholar 

  18. Muller, H. J. Eugenics, Genetics and the Family: Proceedings of the Second International Congress of Eugenics Vol. 1 (ed. History, A. M.) (William and Wilkens, Baltimore, 1923).

    Google Scholar 

  19. Muller, H. J. in The New Systematics (ed. Huxley, J. S.) 185–268 (Clarendon Press, Oxford, 1940).

    Google Scholar 

  20. Muller H. J. The Darwinian and modern conceptions of natural selection. Proc. Am. Phil. Soc. 93, 459–470 (1949).

    CAS  Google Scholar 

  21. Mather, K. Polygenic inheritance and natural selection. Biol. Rev. 18, 32–64 (1943).

    Google Scholar 

  22. Mather, K. Biometrical Genetics (Dover, New York, 1949).

    Google Scholar 

  23. Huxley, J. Evolution as a Process (Unwin Bros, Woking; London, 1954).

    Google Scholar 

  24. Huxley, J. Evolution, the Modern Synthesis (George Allen & Unwin, London, 1942).

    Google Scholar 

  25. Orr, H. A. & Coyne, J. A. The genetics of adaptation revisited. Am. Nat. 140, 725–742 (1992).

    CAS  PubMed  Google Scholar 

  26. Tanksley, S. D. Mapping polygenes. Annu. Rev. Genet. 27, 205–233 (1993).

    CAS  PubMed  Google Scholar 

  27. Falconer, D. S. & Mackay, T. F. C. Introduction to Quantitative Genetics (Longman, Harlow, England, 1996).

    Google Scholar 

  28. Kearsey, M. J. & Farquhar, G. L. QTL analysis in plants; where are we now? Heredity 80, 137–142 (1998).

    PubMed  Google Scholar 

  29. Orr, H. A. The genetics of species differences. Trends Ecol. Evol. 16, 343–350 (2001).

    Google Scholar 

  30. Mackay, T. F. C. Quantitative trait loci in Drosophila. Nature Rev. Genet. 2, 11–20 (2001).

    CAS  PubMed  Google Scholar 

  31. Holder, K. & Bull, J. Profiles of adaptation in two similar viruses. Genetics 159, 1393–1404 (2001).

    CAS  PubMed  PubMed Central  Google Scholar 

  32. Bull, J. J. et al. Exceptional convergent evolution in a virus. Genetics 147, 1497–1507 (1997).

    CAS  PubMed  PubMed Central  Google Scholar 

  33. Wichman, H. A., Badgett, M. R., Scott, L. A., Boulianne, C. M. & Bull, J. J. Different trajectories of parallel evolution during viral adaptation. Science 285, 422–424 (1999).

    CAS  PubMed  Google Scholar 

  34. Riehle, M. M., Bennett, A. F. & Long, A. D. Genetic architecture of thermal adaptation in Escherichia coli. Proc. Natl Acad. Sci. USA 98, 525–530 (2001).

    CAS  PubMed  PubMed Central  Google Scholar 

  35. Anderson, J. et al. Mode of selection and experimental evolution of antifungal drug resistance in Saccharomyces cerevisiae. Genetics 163, 1287–1298 (2003).

    CAS  PubMed  PubMed Central  Google Scholar 

  36. Fisher, R. A. Darwinian evolution of mutations. Eugen. Rev. 14, 31–34 (1922).

    CAS  PubMed  PubMed Central  Google Scholar 

  37. Kimura, M. The Neutral Theory of Molecular Evolution (Cambridge Univ. Press, Cambridge, 1983).

    Google Scholar 

  38. Orr, H. A. The population genetics of adaptation: the distribution of factors fixed during adaptive evolution. Evolution 52, 935–949 (1998). A theoretical study of the genetic basis of phenotypic evolution using Fisher's geometric model of adaptation. This study argues that previous claims about adaptation based on Fisher's model were partly mistaken.

    PubMed  Google Scholar 

  39. Orr, H. A. The evolutionary genetics of adaptation: a simulation study. Genet. Res. 74, 207–214 (1999).

    CAS  PubMed  Google Scholar 

  40. Barton, N. The geometry of natural selection. Nature 395, 751–752 (1998).

    CAS  PubMed  Google Scholar 

  41. Barton, N. H. & Keightley, P. D. Understanding quantitative genetic variation. Nature Rev. Genet. 3, 11–21 (2002).

    CAS  PubMed  Google Scholar 

  42. Peck, J. R., Barreau, G. & Heath, S. C. Imperfect genes, Fisherian mutation and the evolution of sex. Genetics 145, 1171–1199 (1997).

    CAS  PubMed  PubMed Central  Google Scholar 

  43. Rice, S. A geometric model for the evolution of development. J. Theor. Biol. 143, 319–342 (1990).

    Google Scholar 

  44. Hartl, D. & Taubes, C. H. Compensatory nearly neutral mutations: selection without adaptation. J. Theor. Biol. 182, 303–309 (1996).

    CAS  PubMed  Google Scholar 

  45. Hartl, D. L. & Taubes, C. H. Towards a theory of evolutionary adaptation. Genetica 102/103, 525–533 (1998).

    Google Scholar 

  46. Poon, A. & Otto, S. P. Compensating for our load of mutations: freezing the meltdown of small populations. Evolution 54, 1467–1479 (2000).

    CAS  PubMed  Google Scholar 

  47. Barton, N. H. The role of hybridization in evolution. Mol. Ecol. 10, 551–568 (2001).

    CAS  PubMed  Google Scholar 

  48. Orr, H. A. Adaptation and the cost of complexity. Evolution 54, 13–20 (2000).

    CAS  PubMed  Google Scholar 

  49. Welch, J. J. & Waxman, D. Modularity and the cost of complexity. Evolution 57, 1723–1734 (2003).

    PubMed  Google Scholar 

  50. Maynard Smith, J. The Scientist Speculates: an Anthology of Partly-Baked Ideas (ed. Good, I. J.) 252–256 (Basic Books, New York, 1962). This introduced the idea of adaptation through a 'sequence space'. Although Maynard Smith considered protein spaces, his ideas had a key role in later thinking about adaptative walks through DNA sequence spaces.

    Google Scholar 

  51. Maynard Smith, J. Natural selection and the concept of a protein space. Nature 225, 563–564 (1970).

    Google Scholar 

  52. Kimura, M. Evolutionary rate at the molecular level. Nature 217, 624–626 (1968).

    CAS  PubMed  Google Scholar 

  53. King, J. L. & Jukes, T. H. Non-Darwinian evolution: random fixation of selectively neutral mutations. Science 164, 788–798 (1969).

    CAS  PubMed  Google Scholar 

  54. Ohta, T. Molecular Evolution and Polymorphism (ed. Kimura, M.) 148–167 (Natl Inst. Genet., Mishima, 1977).

    Google Scholar 

  55. Kimura, M. Model of effectively neutral mutations in which selective constraint is incorporated. Proc. Natl Acad. Sci. USA 76, 3440–3444 (1979).

    CAS  PubMed  PubMed Central  Google Scholar 

  56. Ohta, T. The nearly neutral theory of molecular evolution. Annu. Rev. Ecol. Syst. 23, 263–286 (1992).

    Google Scholar 

  57. Gould, S. J. & Lewontin, R. C. The spandrels of San Marco and the Panglossian paradigm: a critique of the adaptationist program. Proc. R. Soc. Lond. B 205, 581–598 (1979).

    CAS  PubMed  Google Scholar 

  58. Kauffman, S. & Levin, S. Towards a general theory of adaptive walks on rugged landscapes. J. Theor. Biol. 128, 11–45 (1987). This paper introduced the idea of adaptation over fitness landscapes of varying ruggedness. Although it largely focused on 'random' landscapes, the paper gave rise to a large literature on landscapes of different ruggedness.

    CAS  PubMed  Google Scholar 

  59. Kauffman, S. A., Weinberger, E. D. & Perelson, A. S. in Theoretical Immunology: Part One (ed. Perelson, A. S.) 349–382 (Addison-Wesley, New York, 1988).

    Google Scholar 

  60. Kauffman, S. A. The Origins of Order (Oxford Univ. Press, New York, 1993).

    Google Scholar 

  61. Weinberger, E. A more rigorous derivation of some properties of uncorrelated fitness landscapes. J. Theor. Biol. 134, 125–129 (1988).

    Google Scholar 

  62. Weinberger, E. Correlated and uncorrelated fitness landscapes and how to tell the difference. Biol. Cybern. 63, 325–336 (1990).

    Google Scholar 

  63. Weinberger, E. D. Local properties of Kauffman's N-k model: a tunably rugged energy landscape. Phys. Rev. A 44, 6399–6413 (1991).

    CAS  PubMed  Google Scholar 

  64. Macken, C. A. & Perelson, A. S. Protein evolution on rugged landscapes. Proc. Natl Acad. Sci. USA 86, 6191–6195 (1989).

    CAS  PubMed  PubMed Central  Google Scholar 

  65. Macken, C. A., Hagan, P. S. & Perelson, A. S. Evolutionary walks on rugged landscapes. SIAM J. Appl. Math. 51, 799–827 (1991).

    Google Scholar 

  66. Flyvbjerg, H. & Lautrup, B. Evolution in a rugged fitness landscape. Phys. Rev. A 46, 6714–6723 (1992).

    CAS  PubMed  Google Scholar 

  67. Fontana, W. et al. RNA folding and combinatory landscapes. Phys. Rev. E 47, 2083–2099 (1993).

    CAS  Google Scholar 

  68. Stadler, P. F. & Happel, R. Random field models for fitness landscapes. J. Math. Biol. 38, 435–478 (1999).

    Google Scholar 

  69. Macken, C. A. & Stadler, P. F. in 1993 Lectures in Complex Systems (eds Nadel, L. & Stein, D. L.) 43–86 (Addison-Wesley, Reading, Massachusetts, 1995).

    Google Scholar 

  70. Wright, S. Evolution in Mendelian populations. Genetics 16, 97–159 (1931).

    CAS  PubMed  PubMed Central  Google Scholar 

  71. Wright, S. The roles of mutation, inbreeding, crossbreeding, and selection in evolution. Proc. Sixth Intl Cong. Genet. 1, 356–366 (1932).

    Google Scholar 

  72. Gavrilets, S. Fitness Landscapes and the Origin of Species (Princeton Univ. Press, Princeton, 2004).

    Google Scholar 

  73. Perelson, A. S. & Macken, C. A. Protein evolution on partially correlated landscapes. Proc. Natl Acad. Sci. USA 92, 9657–9661 (1995).

    CAS  PubMed  PubMed Central  Google Scholar 

  74. Anderson, P. W. in Emerging Synthesis in Science: Proceedings of the Founding Workshop of the Santa Fe Institute (ed. Pines, D.) (Santa Fe Inst., Santa Fe, 1985).

    Google Scholar 

  75. Gillespie, J. H. A simple stochastic gene substitution model. Theor. Popul. Biol. 23, 202–215 (1983).

    CAS  PubMed  Google Scholar 

  76. Gillespie, J. H. Molecular evolution over the mutational landscape. Evolution 38, 1116–1129 (1984). This is Gillespie's most extensive discussion of the use of extreme value theory in the study of molecular evolution.

    CAS  PubMed  Google Scholar 

  77. Gillespie, J. H. The Causes of Molecular Evolution (Oxford Univ. Press, Oxford, 1991).

    Google Scholar 

  78. Gumbel, E. J. Statistics of Extremes (Columbia Univ. Press, New York, 1958).

    Google Scholar 

  79. Leadbetter, M. R., Lindgren, G. & Rootzen, H. Extremes and Related Properties of Random Sequences and Processes (Springer, New York, 1983).

    Google Scholar 

  80. Embrechts, P. (ed.) Extremes and Integrated Risk Management (Risk Books, London, 2000).

    Google Scholar 

  81. Stadler, P. F. Biological Evolution and Statistical Physics (eds Lassig, M. & Valleriani, A.) 183–204 (Springer, Berlin, 2002).

    Google Scholar 

  82. Glick, N. Breaking records and breaking boards. Am. Math. Monthly 85, 2–26 (1978).

    Google Scholar 

  83. Arnold, B. C., Balakrishnan, N. & Nagaraja, H. N. Records (John Wiley and Sons, New York, 1998).

    Google Scholar 

  84. Gillespie, J. H. Is the population size of a species relevant to its evolution? Evolution 55, 2161–2169 (2003).

    Google Scholar 

  85. Gillespie, J. H. Natural selection and the molecular clock. Mol. Biol. Evol. 3, 138–155 (1986).

    CAS  PubMed  Google Scholar 

  86. Gillespie, J. H. Molecular evolution and the neutral allele theory. Oxford Surv. Evol. Biol. 4, 10–37 (1989).

    Google Scholar 

  87. Gerrish, P. The rhythm of microbial adaptation. Nature 413, 299–302 (2001).

    CAS  PubMed  Google Scholar 

  88. Orr, H. A. The distribution of fitness effects among beneficial mutations. Genetics 163, 1519–1526 (2003).

    CAS  PubMed  PubMed Central  Google Scholar 

  89. Rozen, D. E., de Visser, J. A. G. M. & Gerrish, P. J. Fitness effects of fixed benefical mutations in microbial populations. Curr. Biol. 12, 1040–1045 (2002).

    CAS  PubMed  Google Scholar 

  90. Orr, H. A. The population genetics of adaptation: the adaptation of DNA sequences. Evolution 56, 1317–1330 (2002). This paper brought the extreme value theory to bear on several key questions in the study of DNA sequence adaptation.

    CAS  PubMed  Google Scholar 

  91. Orr, H. A. The probability of parallel adaptation. Evolution (in the press).

  92. Orr, H. A. Theories of adaptation: what they do and don't say. Genetica (in the press).

  93. Imhof, M. & Schlotterer, C. Fitness effects of advantageous mutations in evolving Escherichia coli populations. Proc. Natl Acad. Sci. USA 98, 1113–1117 (2001).

    CAS  PubMed  PubMed Central  Google Scholar 

  94. Sanjuan, R., Moya, A. & Elena, S. F. The distribution of fitness effects caused by single-nucleotide substitutions in an RNA virus. Proc. Natl Acad. Sci. USA 101, 8396–8401 (2004).

    CAS  PubMed  PubMed Central  Google Scholar 

  95. Liu, J. et al. Genetic analysis of a morphological shape difference in the male genitalia of Drosophila simulans and D. mauritiana. Genetics 142, 1129–1145 (1996).

    CAS  PubMed  PubMed Central  Google Scholar 

  96. Fisher, R. A. The Genetical Theory of Natural Selection: a Complete Variorum Edition (Oxford Univ. Press, Oxford, 2000).

    Google Scholar 

  97. Colosimo, P. F. et al. The genetic architecture of parallel armor plate reduction in threespine sticklebacks. PLoS Biol. 2, e109 (2004).

    PubMed  PubMed Central  Google Scholar 

  98. Cresko, W. A. et al. Parallel genetic basis for repeated evolution of armor loss in Alaskan threespine stickleback populations. Proc. Natl Acad. Sci. USA 101, 6050–6055 (2004).

    CAS  PubMed  PubMed Central  Google Scholar 

  99. Shapiro, M. D. et al. Genetic and developmental basis of evolutionary pelvic reduction in threespine sticklebacks. Nature 428, 717–723 (2004). Experimental analysis that identified a candidate gene, Pitx1 , that has an important role in the morphological adaptation of marine sticklebacks to lake environments.

    CAS  PubMed  Google Scholar 

  100. Sucena, E. & Stern, D. L. Divergence of larval morphology between Drosophila sechellia and its sibling species caused by cis-regulatory evolution of ovo/shaven-baby. Proc. Natl Acad. Sci. USA 97, 4530–4534 (2000).

    CAS  PubMed  PubMed Central  Google Scholar 

  101. White, S. & Doebley, J. Of genes and genomes and the origin of maize. Trends Genet. 14, 327–332 (1998).

    CAS  PubMed  Google Scholar 

  102. Wang, R. -L., Stec, A., Hey, J., Lukens, L. & Doebley, J. The limits of selection during maize domestication. Nature 398, 236–239 (1999).

    CAS  PubMed  Google Scholar 

  103. Doebley, J. The genetics of maize evolution. Annu. Rev. Genet. 38, 37–59 (2004). A comprehensive and up-to-date review of Doebley's classical studies of the genetic basis of maize domestication.

    CAS  PubMed  Google Scholar 

  104. Bradshaw, H. D., Wilbert, S. M., Otto, K. G. & Schemske, D. W. Genetic mapping of floral traits associated with reproductive isolation in monkeyflowers (Mimulus). Nature 376, 762–765 (1995).

    CAS  Google Scholar 

  105. Bradshaw, H. D., Otto, K. G., Frewen, B. E., McKay, J. K. & Schemske, D. W. Quantitative trait loci affecting differences in floral morphology between two species of Monkeyflower (Mimulus). Genetics 149, 367–382 (1998). An early and important QTL analysis that implicates the major genes in the natural adaptation of plant species to their pollinators.

    CAS  PubMed  PubMed Central  Google Scholar 

  106. Bradshaw, H. D. & Schemske, D. W. Allele substitution at a flower colour locus produces a pollinator shift in monkeyflowers. Nature 426, 176–178 (2003).

    CAS  PubMed  Google Scholar 

  107. Leigh, E. G. Ronald Fisher and the development of evolutionary theory. II. Influences of new variation on evolutionary process. Oxford Surv. Evol. Biol. 4, 212–264 (1987).

    Google Scholar 

  108. Otto, S. P. & Jones, C. D. Detecting the undetected: estimating the total number of loci underlying a trait in QTL analyses. Genetics 156, 2093–2107 (2000).

    CAS  PubMed  PubMed Central  Google Scholar 

  109. David, H. A. Order Statistics (John Wiley and Sons, New York, 1970).

    Google Scholar 

  110. Weissman, I. Estimation of parameters and large quantiles based on the kth largest observations. J. Am. Stat. Assoc. 73, 812–815 (1978).

    Google Scholar 

  111. Coyne, J. A. & Orr, H. A. Speciation (Sinauer Associates Inc., Sunderland, Massachusetts, 2004).

    Google Scholar 

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Acknowledgements

This work was supported by a grant from the US National Institutes of Health.

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  1. Department of Biology, University of Rochester, Rochester, 14627, New York, USA

    H. Allen Orr

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Glossary

STANDING GENETIC VARIATION

Allelic variation that is currently segregating within a population; as opposed to alleles that appear by new mutation events.

FITNESS

A quantity that is proportional to the mean number of viable, fertile progeny produced by a genotype.

DEFICIENCY MAPPING

A type of genetic mapping that uses chromosomal deletions to 'uncover' recessive alleles that affect a trait.

COMPLEMENTATION TESTS

The use of genetically defined knockout mutations to identify loci that affect a trait.

BIOMETRIC

An approach to the study of phenotypes that emphasizes quantitative measurements (such as of body size) and statistical analysis.

CONTINUOUS CHARACTER

A trait (such as body size) that varies smoothly (continuously) in magnitude; as opposed to discrete characters.

EPISTATIC INTERACTION

Any non-additive interaction between two or more mutations at different loci, such that their combined effect on a phenotype deviates from the sum of their individual effects.

ADDITIVE GENETIC VARIANCE

The part of the total genetic variation that is due to the main (or additive) effects of alleles on a phenotype; as opposed to the dominance and epistatic variances. The additive variance determines the degree of resemblance between relatives and therefore the response to selection.

QUANTITATIVE TRAIT LOCUS

(QTL). A mapped chromosomal region that has a detectable effect on a phenotypic difference between two populations or species. A QTL does not necessarily correspond to a single gene, but can reflect several linked genes.

MICROBIAL EXPERIMENTAL EVOLUTION

An experimental approach that involves the 'real time' adaptation of microbes (typically bacteria, phage or yeast) to defined laboratory conditions.

COMPENSATORY EVOLUTION

Evolution in which a second substitution compensates for the deleterious effects of an earlier substitution.

MUTATION LOAD

The decrease in population fitness below its ideal value owing to recurrent deleterious mutation.

MODULARITY

The idea that organisms are broken developmentally into roughly independent modules, such that mutations affecting traits in one module do not affect traits in other modules.

SHIFTING BALANCE THEORY

A largely verbal theory of evolution which maintains that the interaction between natural selection, genetic drift and migration is more important that the action of any single force. Sewall Wright argued that this theory helped to explain how species could effectively search for the global, and not merely local, optimum.

AFFINITY MATURATION

An increase in the affinity of an antibody for an antigen which is seen as an immune response improves.

SPIN GLASSES

Magnetic objects that are disordered and in which adjacent dipoles can either 'point' in the same direction or in opposite directions.

MOLECULAR CLOCK

The empirical finding that a particular type of protein or DNA sequence evolves at a nearly constant rate through time.

POISSON PROCESS

A simple statistical process in which there is a small and constant probability of change during each short interval of time.

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Orr, H. The genetic theory of adaptation: a brief history. Nat Rev Genet 6, 119–127 (2005). https://doi.org/10.1038/nrg1523

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