Skip to main content Accessibility help
Hostname: page-component-55597f9d44-54vk6 Total loading time: 0.895 Render date: 2022-08-09T17:13:08.100Z Has data issue: true Feature Flags: { "shouldUseShareProductTool": true, "shouldUseHypothesis": true, "isUnsiloEnabled": true, "useRatesEcommerce": false, "useNewApi": true } hasContentIssue true

The Missing Two-Thirds of Evolutionary Theory

Published online by Cambridge University Press:  25 February 2020

Robert N. Brandon
Duke University, North Carolina
Daniel W. McShea
Duke University, North Carolina


In this Element, we extend our earlier treatment of biology's first law. The law says that in any evolutionary system in which there is variation and heredity, there is a tendency for diversity and complexity to increase. The law plays the same role in biology that Newton's first law plays in physics, explaining what biological systems are expected to do when no forces act, in other words, what happens when nothing happens. Here we offer a deeper explanation of certain features of the law, develop a quantitative version of it, and explore its consequences for our understanding of diversity and complexity.
Get access
Online ISBN: 9781108591508
Publisher: Cambridge University Press
Print publication: 26 March 2020

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)


Adamowicz, S. J., Purvis, A., and Wills, M. A.. 2008. Increasing morphological complexity in multiple parallel lineages of the Crustacea. Proceedings of the National Academy of Sciences of the United States of America 105: 4786–91.CrossRefGoogle ScholarPubMed
Bell, G., and Mooers, A. O.. 1997. Size and complexity among multicellular organisms. Biological Journal of the Linnean Society 60: 345–63.CrossRefGoogle Scholar
Bonner, J. T. 1988. The Evolution of Complexity by Means of Natural Selection. Princeton University Press, Princeton.Google Scholar
Bonner, J. T. 2004. Perspective: The size-complexity rule. Evolution 58:1883–90.CrossRefGoogle ScholarPubMed
Bookstein, F. L. 1988. Random walk and the biometrics of morphological characters. Evolutionary Biology 23: 369–98.CrossRefGoogle Scholar
Brandon, R. N. 1990. Adaptation and Environment. Princeton University Press, Princeton.Google Scholar
Brandon, R. N. 2006. The principle of drift: Biology’s first law. Journal of Philosophy 103: 319–35.CrossRefGoogle Scholar
Brandon, R. N., and Antonovics, J.. 1996. The coevolution of organism and environment. Pp. 161–78 in Brandon, R. N. (ed.), Concepts and Methods in Evolutionary Biology. Cambridge University Press, Cambridge.Google Scholar
Bromham, L. 2011. Wandering drunks and general lawlessness in biology: Does diversity and complexity tend to increase in evolutionary systems? Biology and Philosophy 26: 915–33.CrossRefGoogle Scholar
Brunet, T. D. P., and Doolittle, W. F.. 2018. The generality of constructive neutral evolution. Biology and Philosophy 33: 125.CrossRefGoogle Scholar
Buchholtz, E. A., and Wolkovich, E. H.. 2005. Vertebral osteology and complexity in Lagenorhynchus acutus. Marine Mammal Science 21: 411–28.CrossRefGoogle Scholar
Ciampaglio, C. N., Kemp, M., and McShea, D. W.. 2001. Detecting changes in morphospace occupation patterns in the fossil record: Characterization and analysis of measures of disparity. Paleobiology 27: 695715.2.0.CO;2>CrossRefGoogle Scholar
Damuth, J. 1985. Selection among “species”: A formulation in terms of natural functional units. Evolution 39: 1132–46.Google ScholarPubMed
Darwin, C. 1859. On the Origin of Species. John Murray, London.Google Scholar
Darwin, C. 1987. Notebook E. Charles Darwin’s Notebooks, 1836–1844. Barrett, P. H., Gautrey, P. J., Herbert, S., Kohn, D., and Smith, S. (Eds.), Geology, Transmutation of Species, Metaphysical Enquiries. Cornell University Press, Ithaca.Google Scholar
Deline, B., Greenwood, J.M., Clark, J.W., Puttick, M.N., Peterson, K.J., and Donoghue, P.C.J.. 2018. Evolution of metazoan morphological disparity. Proc Natl Acad Sci USA 15(38): E8909E8918.CrossRefGoogle Scholar
Doolittle, W. F. 2012. A ratchet for protein complexity. Nature 481: 270–71.CrossRefGoogle ScholarPubMed
Drury, J. P., Grether, G. F., Garland, T. Jr., and Morlon, H.. 2018. An assessment of phylogenetic tools for analyzing the interplay between interspecific interactions and phenotypic evolution. Systematic Biology 67: 413–27.CrossRefGoogle ScholarPubMed
Eldredge, N. 1985. The Unfinished Synthesis. Oxford University Press, Oxford.Google Scholar
Finnegan, G. C., Hanson-Smith, V., Stevens, T. H., and Thornton, J. W.. 2012. Evolution of increased complexity in a molecular machine. Nature 481: 360–64.Google Scholar
Fleming, L. 2012. Network theory and the formation of groups without evolutionary forces. Evolutionary Biology 39(1): 94105.CrossRefGoogle Scholar
Fleming, L. 2013. The notion of limited perfect adaptedness in Darwin’s principle of divergence. Perspectives on Science 21: 122.CrossRefGoogle Scholar
Fleming, L., and Brandon, R. 2015. Why flying dogs are rare: A general theory of luck in evolutionary transitions. Studies in History and Philosophy of Science, Part C 49: 2431.CrossRefGoogle Scholar
Foote, M. 1994. Morphological disparity in Ordovician-Devonian crinoids and the early saturation of morphological space. Paleobiology 20: 320–44.CrossRefGoogle Scholar
Gingerich, P. D. 1993. Quantification and comparison of evolutionary rates. American Journal of Science 293(A): 453–78.CrossRefGoogle Scholar
Goodman, N. 1955. Fact, Fiction and Forecast. Harvard University Press, Cambridge, MA.Google Scholar
Gould, S. J. 1988. Trends as changes in variance: A new slant on progress and directionality in evolution. Journal of Paleontology 62: 319–29.CrossRefGoogle Scholar
Gould, S. J. 1989. Wonderful Life: The Burgess Shale and the Nature of History. W. W. Norton, New York.Google Scholar
Gould, S. J. 1996. Full House: The Spread of Excellence from Plato to Darwin. Harmony Books, New York.CrossRefGoogle Scholar
Gould, S. J., and Lewontin, R. C.. 1979. The spandrels of San Marco and the panglossian paradigm: A critique of the adaptationist programme. Proceedings of the Royal Society of London, Series B 205: 581–98.Google Scholar
Grant, P. R., and Grant, B. R.. 2006. Evolution of character displacement in Darwin’s finches. Science 313: 224–26.CrossRefGoogle ScholarPubMed
Grant, P. R., and Grant, B. R.. 2008. How and Why Species Multiply: The Radiation of Darwin’s Finches. Princeton University Press, Princeton, NJ.Google Scholar
Gregory, W. K. 1935. Reduplication in evolution. Quarterly Review of Biology 10: 272–90.CrossRefGoogle Scholar
Hansen, T. F., and Martins, E. P.. 1996. Translating between microevolutionary process and macroevolutionary patterns: The correlation structure of interspecific data. Evolution 50: 1404–17.CrossRefGoogle ScholarPubMed
Hempel, C. 1965. Aspects of Scientific Explanation. The Free Press, New York.Google Scholar
Hunt, G. 2006. Fitting and comparing models of phyletic evolution: Random walks and beyond. Paleobiology 32: 578601.CrossRefGoogle Scholar
Hunt, G. 2007. The relative importance of directional change, random walks, and stasis in the evolution of fossil lineages. Proceedings of the National Academy of Sciences of the United States of America 104: 18404–8.CrossRefGoogle ScholarPubMed
Hunt, G., Wicaksono, S. A., Brown, J. E., and Macleod, K.. 2010. Climate-driven body-size trends in the ostracod fauna of the deep Indian Ocean. Palaeontology 53: 1255–68.CrossRefGoogle Scholar
Jablonski, D. 1986. Background and mass extinctions: The alternation of macroevolutionary regimes. Science 231: 129–33.CrossRefGoogle ScholarPubMed
Lande, R. 1976. Natural selection and random genetic drift in phenotypic evolution. Evolution 30: 314–34.CrossRefGoogle ScholarPubMed
Lukeš, J., Archibald, J. M., Keeling, P. J., Doolittle, W. F., and Gray, M. W.. 2011. How a neutral evolutionary ratchet can build cellular complexity. IUBMB Life 63: 528–37.CrossRefGoogle ScholarPubMed
Lynch, M., and Conery, J. S.. 2000. The evolutionary fate and consequence of duplicate genes. Science 290: 1151–55.CrossRefGoogle Scholar
Lynch, M., and Force, A.. 2000. The probability of duplicate gene preservation by subfunctionalization. Genetics 154: 459–73.Google ScholarPubMed
Marcus, J. M. 2005. A partial solution to the C-value paradox. Pp. 97–105 in McLysaght, A. (ed.), Ws on Comparative Genomics. Springer, Berlin.Google Scholar
Maynard Smith, J., and Szathmáry, E.. 1995. The Major Transitions in Evolution. Oxford University Press, Oxford.Google Scholar
McShea, D. W. 1991. Complexity and evolution: What everybody knows. Biology and Philosophy 6: 303–24.CrossRefGoogle Scholar
McShea, D. W. 1993. Evolutionary change in the morphological complexity of the mammalian vertebral column. Evolution 47: 730–40.CrossRefGoogle ScholarPubMed
McShea, D. W. 1994. Mechanisms of large-scale evolutionary trends. Evolution 48: 1747–63.CrossRefGoogle ScholarPubMed
McShea, D. W. 1996. Metazoan complexity and evolution: Is there a trend? Evolution 50: 477–92.Google Scholar
McShea, D. W. 2001. The hierarchical structure of organisms: A scale and documentation of a trend in the maximum. Paleobiology 27: 405–23.2.0.CO;2>CrossRefGoogle Scholar
McShea, D. W. 2002. A complexity drain on cells in the evolution of multicellularity. Evolution 56: 441–52.CrossRefGoogle ScholarPubMed
McShea, D. W. 2005. A universal generative tendency toward increased organismal complexity. Pp. 435–53 in Hallgrimsson, B. and Hall, B. (eds.), Variation: A Central Concept in Biology. Elsevier Academic, Burlington, MA.Google Scholar
McShea, D. W. 2015. Three trends in the history of life: An evolutionary syndrome. Evolutionary Biology 43: 531–42.Google Scholar
McShea, D. W., and Venit, E. P.. 2001. What is a part? Pp. 259–84 in Wagner, G. P. (ed.), The Character Concept in Evolutionary Biology. Academic Press, San Diego, CA.Google Scholar
McShea, D. W., and Brandon, R. N.. 2010. Biology’s First Law. University of Chicago Press, Chicago.CrossRefGoogle Scholar
McShea, D. W., Wang, S. C., and Brandon, R. N.. 2019. A quantitative formulation of biology’s first law. Evolution 73: 1101–15.CrossRefGoogle ScholarPubMed
Mora, C., Tittensor, D. P., Adl, S., Simpson, A. G. B., and Worm, B.. 2011. How many species are there on Earth and in the ocean. PLoS Biology 9: e1001127.CrossRefGoogle ScholarPubMed
Nabi, I. 1981. On the tendencies of motion. Pp. 123–27 in R. Levins and R. Lewontin, The Dialectical Biologist. Harvard University Press, Cambridge, MA.Google Scholar
Nuismer, S. L., and Harmon, L. J.. 2015. Predicting rates of interspecific interaction from phylogenetic trees. Ecology Letters 18: 1727.CrossRefGoogle ScholarPubMed
Odling-Smee, F. J., Laland, K., and Feldman, M. W.. 1996. Niche construction. American Naturalist 147: 641–48.CrossRefGoogle Scholar
O’Malley, M.A., Wideman, J.G., and Ruiz-Trillo, I.. 2016. Losing complexity: The role of simplification in macroevolution. Trends in Ecology and Evolution 31: 608621.CrossRefGoogle ScholarPubMed
Penrose, O. 2005. Foundations of Statistical Mechanics: A Deductive Treatment. Dover, Mineola, NY.Google Scholar
Pfennig, D., and Pfennig, K.. 2012. Evolution’s Wedge: Competition and the Origins of Diversity. University of California Press, Berkeley.CrossRefGoogle Scholar
Raup, D. M. 1977. Stochastic models in evolutionary paleontology. Pp. 5978 in Hallam, A. (ed.), Patterns of Evolution as Illustrated by the Fossil Record. Elsevier, Amsterdam.CrossRefGoogle Scholar
Raup, D. M., and Gould, S. J.. 1974. Stochastic simulation and evolution of morphology – towards a nomothetic paleontology. Systematic Zoology 23: 305–22.CrossRefGoogle Scholar
Revell, L. J., Harmon, L. J., and Collar, D. C.. 2008. Phylogenetic signal, evolutionary process, and rate. Systematic Biology 57: 591601.CrossRefGoogle ScholarPubMed
Roopnarine, P. D., Byars, G., and Fitzgerald, P.. 1999. Anagenetic evolution, stratophenetic patterns, and random walk models. Paleobiology 25: 4157.Google Scholar
Ruse, M. 2009. Monad to Man: The Concept of Progress in Evolutionary Biology. Harvard University Press, Cambridge, MA.Google Scholar
Saunders, P. T., and Ho, M. W. 1976. On the increase in complexity in evolution. Journal of Theoretical Biology 63: 375–84.CrossRefGoogle Scholar
Salmon, W. C. 1971. Statistical Explanation and Statistical Relevance. University of Pittsburgh Press, Pittsburgh, PA.CrossRefGoogle Scholar
Salmon, W. C. 1984. Scientific Explanation and the Causal Structure of the World. Princeton University Press, Princeton, NJ.Google Scholar
Schopf, T. J. M, Raup, D. M., Gould, S. J., and Simberloff, D. S.. 1975. Genomic versus morphologic rates of evolution: Influence of morphologic complexity. Paleobiology 1: 6370.CrossRefGoogle Scholar
Sepkoski, J. J. Jr. 1978. A kinetic model of Phanerozoic taxonomic diversity. I. Analysis of marine orders. Paleobiology 4: 223–51.CrossRefGoogle Scholar
Sheets, H. D., and Mitchell, C. E.. 2001. Why the null matters: Statistical tests, random walks and evolution. Genetica 11213: 105–25.Google ScholarPubMed
Sidor, C. A. 2001. Simplification as a trend in synapsid cranial evolution. Evolution 55: 1419–42.CrossRefGoogle ScholarPubMed
Stanley, S. M. 1973. An explanation for Cope’s Rule. Evolution 27: 116.CrossRefGoogle ScholarPubMed
Stanley, S. M. 1975. A theory of evolution above the species level. Proceedings of the National Academy of Sciences of the United States of America 72: 646–50.CrossRefGoogle ScholarPubMed
Stanley, S. M. 1979. Macroevolution: Pattern and Process. Johns Hopkins University Press, Baltimore.Google Scholar
Sterelny, K. 1999. Bacteria at the high table. Biology and Philosophy 14: 459–70.CrossRefGoogle Scholar
Sterelny, K. 2016. Contingency and history. Philosophy of Science 83: 521–39.CrossRefGoogle Scholar
Stoltzfus, A. 1999. On the possibility of constructive neutral evolution. Journal of Molecular Evolution 49: 169–81.CrossRefGoogle ScholarPubMed
Valentine, J. W., Collins, A. G., and Meyer, C. P.. 1994. Morphological complexity increase in metazoans. Paleobiology 20: 131–42.CrossRefGoogle Scholar
Vlieger, L. 2019. Book review – Biology's First Law: The Tendency for Diversity & Complexity to Increase in Evolutionary Systems. The Inquisitive Biologist (blog). Scholar
Waddington, C. H. 1969. Paradigm for an evolutionary process. Pp. 106–28 in Waddington, C. H. (ed.), Towards a Theoretical Biology, vol. 2. Edinburgh University Press, Edinburgh.Google Scholar
Williston, S. 1914. Water Reptiles of the Past and Present. University of Chicago Press, Chicago.CrossRefGoogle Scholar
Cited by

Save element to Kindle

To save this element to your Kindle, first ensure is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.

Note you can select to save to either the or variations. ‘’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.

Find out more about the Kindle Personal Document Service.

The Missing Two-Thirds of Evolutionary Theory
Available formats

Save element to Dropbox

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.

The Missing Two-Thirds of Evolutionary Theory
Available formats

Save element to Google Drive

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.

The Missing Two-Thirds of Evolutionary Theory
Available formats