History, Part I: A Brief History of Epigenetics

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by Shea Robison (@EpigeneticsGuy)

In the history of modern Western evolutionary theory, the first use of the term epigenetics is generally attributed to Conrad Waddington in an article published in 1942.[1]  In this article Waddington used epigenetics as the name for the study of the causal mechanisms through which genes bring about their phenotypic effects and which necessarily involve adaptive interaction with the environment (although it bears mentioning that the ‘epigenetics’ of Waddington was rooted exclusively in embryology and development, and is not quite the epigenetics of today with its emphasis on non-genetic inheritance, but is better conceived of as “developmental genetics”[2]).  Years before this 1942 article Waddington had proposed the appearance of particular organs as the product of the interactions of the genotype and what he called the “epigenotype” with the external environment.[3]  He then subsequently developed this idea of an epigenotype into the more general notion of epigenetics.

For Waddington, the promotion of the epigenotype as a distinct biological layer and the recognition of epigenetics as distinct processes in biological development were necessary steps for the progress of genetics because this nexus of genome, epigenome and environment had been so maligned by the prevailing gene-centered scientific consensus of genetics, which overlooked important evidence that could contribute to a more complete understanding of biological development.  Importantly, Waddington’s original project in promoting the explicit recognition of this biological layer between the genome and the environment was not to challenge but to extend the conventional understanding of genetics through a more sophisticated approach which bridges the gap between the genotype and the developing phenotype.[4]

As mentioned in the introduction, according to the then and current dominant scientific interpretation of genetics, genes are isolated from their environments; therefore genetic change is not a function of immediate environmental influence, but is rather a result of random mutations and sexual recombination; as a result, adaptations are ultimately a population-level phenomena which result from natural selection.  The countervailing theory that adaptive characteristics acquired during the life of an organism can be passed on to future generations is generally attributed to Jean-Baptise Lamarck (1744-1829), and often referred to as Lamarckism.  The classic example of Lamarckian inheritance is that giraffe necks elongated as a result of giraffes having to stretch to reach available forage located higher and higher in the trees, which reaching physically stretched the necks of giraffes in one generation, which elongated necks were then passed on to their offspring in the next generation.  Because the necks of these subsequent generations were elongated they were able to reach higher into the trees, which raised the height of available forage, thereby requiring even further stretching, and so on, thus resulting in the very long necks of the giraffe species.[5]

However, for all its seemingly intuitive plausibility, because of the preeminence of the ontological commitments of genetics in the Modern Synthesis, this Lamarckian “soft inheritance”[6] is now generally dismissed as a rather quaint pre-Mendelian theory of evolution.  As will be discussed in more detail in the section on epigenetics research, there are many evolutionary scientists and biologists working in epigenetics today who are able to show this blanket dismissal of epigenetics has been misguided.  Even some mainstream scientists dispute the common perception of Lamarck’s thought as an unfair oversimplification that discredits the actual depth of Lamarck’s more comprehensive evolutionary theory,[7] and advocate for the inclusion of at least some Lamarckian concepts.[8]  For example, Stephen Jay Gould praises Lamarck for so strongly emphasizing “the active role of organisms as creators of their environment” as an aspect of contemporary evolutionary theory that is often overlooked, but then stipulates that “this, and only this” is valid Lamarckism.[9]  Regardless, for the most part Lamarckian epigenetics-based ideas have been “decisively” rejected by scientific consensus in favor of Darwinian natural selection for integration with Mendelian genetics to become the Modern Synthesis of evolutionary thought.[10]

As a result of the historical precedents behind the development of the Modern Synthesis,[11] despite all the empirical evidence Waddington and others had been able to marshal in demonstration of the role of the epigenotype in phenotypic plasticity[12] and in non-genetic inheritance,[13] epigenetics was in Waddington’s words still “so completely rejected by the rest of the scientific world that it is hardly considered to be worthy of discussion.”[14]  This blanket rejection of the evidence in favor of epigenetics is for Waddington not the inevitable and justifiable outcome of scientific progress but rather proof of the “extremist” nature of the Modern Synthesists who in their practically exclusive focus on genetic adaptation neglect “the doctrines emerging from other fields of modern biology” which could be combined with genetics to produce significantly different (and ostensibly more comprehensive) conclusions.[15]  Unfortunately for both Waddington and for the Modern Synthesis, the begrudging acceptance of epigenetics has had to wait for another seventy or so years.

I am curious to hear what you think. Leave your comments below and I will respond.

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Next: Epigenetics and the Politics of Science

[1] Waddington C.H. (1942). The epigenotype. Endeavour 1: 18.

[2] Gilbert, S. F. (2012). Commentary: ‘The Epigenotype’ by C.H. Waddington. International Journal of Epidemiology, 41(1), 20-23.

[3]Waddington C.H. (1939). An introduction to modern genetics. Macmillan, New York.

[4] Waddington C.H. (1940). Organisers and Genes. Cambridge: Cambridge University Press; Gilbert, S. F. (2012). Commentary: ‘The Epigenotype’ by C.H. Waddington. International Journal of Epidemiology, 41(1), 20-23; Jablonka, E., & Lamb, M. (2012). Commentary: The epigenotype—a dynamic network view of development. International Journal of Epidemiology, 41(1), 16-20.

[5] Lamarck, Jean-Baptiste. [1809] 2011. Zoological Philosophy: An Exposition with Regard to the Natural History of Animals. Cambridge: Cambridge University Press, 106-127; Moore, J. N. 1970. Biology: a search for order in complexity. Grand Rapids: Zondervan Pub. House.

[6] Mayr, Ernst. 1980. “Prologue: Some Thoughts on the History of the Evolutionary Synthesis.” In The Evolutionary synthesis: perspectives on the unification of biology, eds. William B. Provine and Ernst Mayr. Cambridge: Harvard University Press.

[7] Gershenowitz, H. 1984. “Professor Conway Zirkle’s Vitriolic Attack on Lamarck.” Indian Journal of History of Sciecne 19(3): 261-71.

[8] Gould, S. J. 2002. The structure of evolutionary theory. Cambridge, Mass.: Belknap Press of Harvard University Press, 170-5.

[9] Gould, S. J. 1980. “Shades of Lamarck.” In The panda’s thumb: more reflections in natural history. New York: Norton..

[10] Bowler, Peter J. (2003). Evolution: the History of an Idea (3rd ed.). California: University of California Press, 92-4; 244-5; 333.

[11] Haig D. (2012). The epidemiology of epigenetics. International of Journal of Epidemiology 41:13–16.

[12] Kirpichnikov, V. S. (1947). The problem of nonhereditary adaptive modifications (coincident or organic selection). J. Genet, 48(2), 164-175; Snyder, L. H. (1950). CONCLUDING REMARKS OF THE CHAIRMAN. In Cold Spring Harbor Symposia on Quantitative Biology (Vol. 15, pp. 159-164). Cold Spring Harbor Laboratory Press.

[13] Russell, E. (1942). The Inheritance of Tumors in Drosophila Melano-Gaster, with  Special Reference to an Isogenic Strain of St Sr Tumor 36AL. Genetics 27(622); Waddington, C. H. (1942). Canalization of Development and the Inheritance of Acquired Characters. Nature 150 (3811), 563-565; Mitchell M.B., Mitchell H.K. (1952). A case of “maternal” inheritance in Neurospora crassa. Proc. Natl. Acad. Sci. U.S.A. 38 (5): 442–9; Ephrussi B (1958). The cytoplasm and somatic cell variation. J Cell Comp Physiol 52 Suppl 1:35-53.

[14] Waddington C.H. (1953). The strategy of the genes. George Allen & Unwin, London.

[15] Waddington C.H. (1953). The strategy of the genes. George Allen & Unwin, London.

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6 thoughts on “History, Part I: A Brief History of Epigenetics

  1. […] In this post and this post I discuss the first divergence of epigenetics and genetics in the 1920s, which had both scientific and less-than-scientific components to it, and in this post and this post I discuss some of the political (i.e., non-scientific) reasons for the subsequent…stigmatization (for lack of a better word) of epigenetics until fairly recently. My question through all of these posts is what if these circumstances were different during these  pivotal times? […]

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