Epigenetics and the Extended Synthesis


by Shea Robison (@EpigeneticsGuy)

Epigenetics is just one aspect of what is being called the Extended Synthesis of evolutionary biology[1], in distinction to what is referred to as the Modern Synthesis of evolutionary biology. This Modern Synthesis is the fusion of Mendelian genetics with Darwinian evolution as interpreted through the theory and practice of population (i.e., statistical) genetics[2]. This integration of ideas is called the Modern Synthesis because until the synthesizing work of Theodosius Dobzhansky and others during the 1920s, 1930s and 1940s, Mendelian genetics and Darwinian evolution were actually competing and seemingly irreconcilable paradigms[3].

The major tenets of the Modern Synthesis can be summarized as 1) that populations contain genetic variation which arises by random (i.e., not adaptively directed) mutation and recombination; 2) that populations evolve by changes in gene frequency through random genetic drift, gene flow, and especially natural selection; 3) and that most individual phenotypic effects are very slight, so that most phenotypic changes are very gradual[4].

The most salient aspects of the Modern Synthesis in the context of this post are first, the emphasis on populations and not on individuals in describing variation; second, the emphasis on randomness as the source of variation; third, the lack of adaptiveness (i.e., lack of responsiveness to the immediate environment) which results from this assumption of randomness as the source of variation; and, finally, that phenotypic variation is very slight and very gradual. Epigenetics poses significant challenges to each of these basic. assumptions

While each of these tenets was derived through scientific methods, for all their scientific pretenses each of these assumptions have a long non-scientific history which predates their incorporation as tenets of the Modern Synthesis. These tenets and their attendant assumptions constitute a very specific ethical framework which allows certain interpretations of behaviors and outcomes and excludes others. However, this framework and these ethical implications of these scientific assumptions are often not recognized as such. What is this underlying ethical framework of genetics and what are the politics which result from this framework will be discussed, but the main point is that these ‘scientific’ assumptions are actually the doorway through which ethics and politics steal into the henhouse of science.

The Extended Synthesis in one sense, as indicated by the name, is properly understood as the extension of the Modern Synthesis and not its replacement. As explained by Massimo Pigliucci:

Let me again be clear on a fundamental point underlying this whole discussion: one can reasonably argue that none of this contradicts any tenet of the [Modern Synthesis], although it seems to me at least reasonable to concede that the new concepts and empirical findings…may eventually force a shift of emphasis away from the population genetic-centered view of evolution that characterizes the [Modern Synthesis][5].

In this sense at least the Extended Synthesis and its constituent parts are not fundamental challenges to genetics. In particular, according to Pigliucci, this shift of emphasis merely involves the incorporation into conventional genetics and developmental biology of concepts such as evolvability, phenotypic plasticity, epigenetics, complexity and the nonlinearity of adaptation in high-dimension adaptive landscapes[6].

However, this point of view does not consider the ethical implications of these extensions of conventional genetics. At the level of science, it is probable that these ideas can eventually be incorporated into the theoretical structure of genetics without too much difficulty, but this does not consider the possible ethical and political issues that might be involved. In fact, there are likely far more science-based reasons for their inclusion than for their exclusion, which actually makes the exclusion of fields like epigenetics from genetics that much more of a puzzle: If there are so many science-based reasons for the inclusion of epigenetics within genetics, why has it been so maligned for so long? A plausible answer is that there are even stronger non-scientific reasons for this exclusion of epigenetics, and my working theory in this post is that these non-scientific reasons are a function of key differences in the ‘hidden’ ethical commitments of epigenetics and conventional genetics. Thus, again the focus of this post is on first revealing the unseen ethical commitments behind conventional genetics, then elaborating the ethical commitments of epigenetics, and analyzing the political implications of these new ethical challenges presented by the (re)emergence of epigenetics.

Also, at this point I do not know if the other components of the Extended Synthesis share the same background ethical commitments as epigenetics and therefore constitute a coherent ethical whole as does the Modern Synthesis, or if the ethical commitments of these different components are unique from each other, or much else about the ethical landscape of the Extended Synthesis. My assumption is that the underlying ethics of these other components of the Extended Synthesis will at the least be more similar to those of epigenetics than of conventional genetics, but this is work that will have to wait.

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

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[1] Pigliucci, M. & Muller, G. (2010). Evolution: The Extended Synthesis. Cambridge, Mass.: MIT Press.

[2] Mayr, E. (1980). The Evolutionary synthesis: perspectives on the unification of biology. Cambridge, Mass.: Harvard University Press.

[3] Burian, R. (2005). The Epistemology of Development, Evolution, and Genetics. Cambridge: Cambridge University Press. See also Bowler, P. J. (1983). The Eclipse of Darwinism. Baltimore: The Johns Hopkins University Press; Bowler, P. J. (1988). The Non-Darwinian Revolution. Baltimore, MD: Johns Hopkins University Press; Bowler, P. J. (1989). The Mendelian Revolution. Baltimore, MD: Johns Hopkins University Press; Depew, D. J., and B. H. Weber (1995). Darwinism Evolving : Systems Dynamics and the Genealogy of Natural Selection. Cambridge, MA: MIT Press; Gayon, J. (1998). Darwinism’s Struggle for Survival: Heredity and the Hypothesis of Natural Selection. Translated by M. Cobb. Cambridge: Cambridge University Press; Provine, W. B. (1971). The Origins of Theoretical Population Genetics. Chicago: Chicago University Press.

[4] Futuyama, Douglas (1986). Evolutionary Biology. Sunderland, MA: Sinauer: 12.

[5] Pigliucci, Massimo (2007). “Do We Need an Extended Evolutionary Synthesis?” Evolution 61(12): 2743-2749.

[6] Pigliucci, Massimo (2007). “Do We Need an Extended Evolutionary Synthesis?” Evolution 61(12): 2743-2749.


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