Excerpt from my book Epigenetics and Public Policy The Tangled Web of Science and Politics now available from my publisher here and at Amazon
One of the roots of the decades-long delay in the acceptance of epigenetics is found in the divergence of emphasis in biology between the emerging science of genetics and the more established field of embryology in the 1930s and 1940s. As will be discussed, this divergence had material, methodological, and geographical aspects. My contention is that this divergence also had substantial political and ideological aspects which were to become even more apparent in the onset of the Second World War, as these ostensible methodological differences also mirrored these impending political fractures.
This schism between embryology and genetics also complicates the conventional picture of the development of science as a logical, inevitable progression, and of the differences between fields as merely the result of a functional division of labor. Instead, at least in this case, this divergence between embryology and genetics appears to have occurred both for scientific reasons, but also as “a struggle for power and authority.”
These dynamics are not exclusive to genetics but seem to be characteristic of science itself. For example, the sociologist Pierre Bordieu and the historian Steven L. Goldman, in their own analyses of the history of science, identify how what often becomes accepted as science is not obviously and necessarily more valid than what is deemed unscientific; instead, legitimate science is often determined just as much by “those who manage to impose the definition of science [as] having, being and doing what they have, are or do,” which outcomes then become justified by assumption after the fact.
In other words, often there are no clear natural distinctions between different possible interpretations of the same natural phenomena, or no objective ways that nature can be ‘carved at its joints,’ and so what come to be the defining assumptions of a science have to be decided by other means. For example, in this case of the schism between genetics and embryology, it is fair to say that neither side was ‘wrong’ as such about the phenomena in question. What was primarily different was in the focus of each, or where the locus of causation was being placed. A legitimate science of biology built upon the work being done in embryology at this time, with genetics as a subsidiary component, is as conceivable as the genetics with embryology as a subsidiary component which actually did develop. In fact, the recent emergence of contemporary epigenetics, in which both these emphases are combined, indicates what such a science would have looked like. The actual result of this schism in biology, though, was a science of biology with the gene as the primary—and practically exclusive—cause.
All this is not to suggest that the science of genetics as it has developed since this time is therefore somehow not legitimate science. It has been an undoubtedly successful scientific enterprise by any standard. This is rather to say that the gene-centric focus of molecular biology is not the only direction a legitimate science of biology could have taken at this particular juncture, and that there were other equally viable alternative routes. That genetics developed as it did, though, is due to both scientific and political factors, although again this observation should not be construed as a condemnation of genetics.
Bricks in their walls
The fields of genetics and embryology had begun to diverge noticeably from each other by the mid-1920s, and this split became definitive by the 1940s—not that embryology disappeared, but that it was relegated or subordinated to genetics. According to the Nobel-prize winning geneticist T.H. Morgan, “an embryologist who inadvertently founded the gene theory,” in his 1934 book Embryology and Genetics, this split was ostensibly along the lines of focus: Genetics and geneticists focused on the transmission of hereditary traits, while embryology and embryologists focused on the expression of those traits.
However, while this may now seem an inevitable division, why such a split was deemed necessary in the first place, and why it should be along the lines of genetics versus embryology, is not so straightforward. This ambiguity is one indication that extra-scientific factors also played a role in this schism, which in turn influenced the timing of the rejection and the eventual begrudging acceptance of epigenetics, which takes more of an embryological approach. For this reason, the underlying social and political currents of this split are of particular relevance to the focus of this book on the policy implications of epigenetics to be discussed in the final section, which are a product of the novelty of epigenetic explanations in the accepted science of genetics.
Notably, this split was facilitated in large part by the work and the influence of Morgan himself, who set the stage for a distinctly American genetics in the 1920s—which would go on to become the prevailing conception of genetics and biology after World War II coincident with the zenith of American global hegemony. Morgan accomplished this division primarily by promoting the nuclear envelope, or the membrane which surrounds the genetic material in cells, as the primary conceptual and disciplinary boundary between genetics and embryology: what occurred within the envelope was the domain of genetics and what occurred outside was the domain of embryology. However, as the historian of biology Jan Sapp observes, the priority Morgan gave to this membrane, and to the disciplinary distinctions which resulted, were not “an intrinsic logical necessity of scientific thought,” but rather “depended directly on both the technical capacity and the institutional power of the discipline within which they were produced.” 
In particular, Morgan’s physiological distinction also highlighted an important geographical difference as well. Most biologists in Europe at this time did not recognize the priority of the physical boundary of the nuclear envelope as asserted by Morgan, but rather considered it to be just one component of the physiology of genes and the cell and the organism. Peter Bowler in his own history of evolutionary thought also notes this key geographical and cultural difference, observing that in Europe “genetics developed in a much less dogmatic form,” with much more interaction between these different subfields, and much more openness even to “non-Darwinian mechanisms of evolution” than in America in particular.
The European approach to biology, in particular as championed by German scientists, asserted that the cytoplasm—or the non-genetic material within a cell not including the nucleus—played an important role in gene function, especially in providing the building material for the chromosomes and the genes themselves. In this way the external environment and the properties of the cells were seen to have a substantial influence on the functions of the genes within the cells. As such, both development and heredity were implicated in this more holistic focus, such that biologists in Europe did not have to confine themselves to studying either inheritance or development, as evidenced by the career of Waddington described elsewhere.
Morgan himself, as an embryologist, was declaring as late as 1910 that “We have come to look upon the problem of heredity as identical to the problem of development,” which was well within this more European and German approach to genes and development. However, by 1926 Morgan the geneticist was asserting that cell composition and structure could be ignored in relation to the genes, such that the explanations of both inheritance and development could be found exclusively within the genes.
The ability of this gene-centered faction of biology to resist absorption by the more established field of embryology constituted what the historian Scott Gilbert identifies as the “last chapter” in the emergence of a particularly American biology, which was to go on to become the prevailing gene-centered conception of biology more generally following World War II. “When had American biology finished ‘emerging’?” Gilbert asks, “I suspect that stage was reached when it had successfully resisted the last attempts to integrate it into European-dominated traditions of inquiry.”
Thus, beyond the legitimate scientific rationales for this emphasis on the nuclear envelope which in part fomented the schism between embryology and genetics, some of the impetus behind this division of fields also stemmed from geneticists asserting their disciplinary independence from embryology, and from the desire of the American school of genetics in particular to assert its independence from the “European-dominated traditions of inquiry” which prioritized embryology and development over a near-exclusive focus on the genes.
Again, per the guiding model of this project, that the sides in these disciplinary quarrels in biology coincided with the eventual sides taken in the Second World War, and that genetics ultimately emerged as the hegemonic victor in biology at the same time the U.S. emerged as the global hegemon after the war, is not merely coincidental. One of the effects of this distinctly Americanized focus on genes which emerged after the Second World War, and which was further solidified during the Cold War, was the antipathy towards epigenetic explanations like those proposed by C.H. Waddington in the 1940s which integrated genetics with embryology. This longstanding antipathy towards epigenenetics resulting in part from this disciplinary divergence of genetics and embryology from before the war helps to explain the timing of the recent (re)emergence of contemporary epigenetics from within genetics. This long delay in the reintegration of epigenetic explanations into genetics in turn helps to explain the political challenges now presented by epigenetics, which are the focus of this book: If epigenetics had been incorporated into the edifice of modern genetics as it was being constructed through the 1940s-1960s—as it very well could have been, given other social and political circumstances—then epigenetics would not present the conceptual and interpretive issues that it does now.
This intra-disciplinary contest between genetics and embryology was just one field of battle in this clash of science, politics, and ideologies during the interwar years. There were many other arenas in which developments in science mirrored the conflicts between political ideologies leading up to both the Second World War and the subsequent Cold War. Describing the circumstances of this convergence of science and ideology on a global scale from before World War Two through the Cold War, and how they pertain to epigenetics, will be the focus of subsequent chapters.
 Sapp, J. (1983). The struggle for authority in the field of heredity, 1900–1932: New perspectives on the rise of genetics. Journal of the History of Biology, 16(3), 311-342.
 Bourdieu, P. (1999). The specificity of the scientific field and the social conditions of the progress of reason. Sociology of Science 14(6): 19-47.
 Goldman, S.L., 2006. Science wars: What scientists know and how they know it. Teaching Company.
 Bourdieu 1999, p. 24.
 Gilbert, S.F. (1991). Cellular politics: Ernest Everett Just, Richard B. Goldschmidt, and the attempt to reconcile embryology and genetics. In Rainger R, Benson KR, Maienschein J. (eds) The American Development of Biology. Philadelphia: University of Pennsylvania Press. Available at http://10e.devbio.com/article.php?id=26
 Morgan, Thomas Hunt. (1934). Embryology and Genetics. New York, NY: Columbia University Press.
 Sapp 1983.
 Bowler, Peter J. (2003). Evolution: the History of an Idea (3rd ed.). California: University of California Press.
 T. H. Morgan, “Chromosomes and Heredity,” American Naturalist, 1910, 44: 449-496.
 T. H. Morgan, “Genetics and the Physiology of Development,” Am. Nat., 1926, 60:459-515.
 Gilbert, S.F. (1991). Cellular politics: Ernest Everett Just, Richard B. Goldschmidt, and the attempt to reconcile embryology and genetics. In Rainger R, Benson KR, Maienschein J. (eds) The American Development of Biology. Philadelphia: University of Pennsylvania Press, p. 311. (Available at http://10e.devbio.com/article.php?id=26)