Epigenetics is just now emerging into the scientific and public awareness seemingly out of nowhere. The results from epigenetics raise a number of significant science-based doubts about many of the fundamental tenets of modern genetics. These challenges to the orthodoxy of genetics spark a significant amount of skepticism about—and outright antagonism towards—epigenetics. However, this antipathy towards epigenetics is nothing new. Many of the ideas and concepts revealed by contemporary epigenetics have been around for centuries, and this resistance to epigenetics goes back just as far.
While there are justifiable scientific reservations about many of the unorthodox claims from epigenetics, the underlying model of my overall project is that much of this resistance both in the past and in the present comes from other than scientific reasons. In reality, there are likely far more science-based reasons for the inclusion of epigenetics within genetics than for its exclusion, which actually makes this exclusion that much more of a puzzle. Explaining this puzzle is a main focus of mine, and requires delving into this convoluted and colorful common history between epigenetics and genetics.This is where Jean-Baptise Lamarck (1744-1829) enters the picture.
The first extensively developed theory for how adaptive characteristics acquired during the life of an organism can be passed on to future generations was formulated by Lamarck, and is often referred to as Lamarckism.
The classic example of Lamarckian inheritance is that of giraffe necks elongating as a result of giraffes having to stretch to reach available forage located higher and higher in the trees. This elongation from the stretching of the necks of giraffes in one generation was then passed on to their offspring in the next generation. Giraffes in these subsequent generations were then able to reach even higher into the trees, which raised the height of available forage, thereby requiring even further stretching which was then passed on to subsequent generations, and so on, thus resulting in the very long necks of the giraffe species.
However, it bears mentioning that this example was not a central aspect of Lamarck’s theoretical exposition of the mechanisms of inheritance. As described by Ron Roizen, Lamarck’s theoretical treatise regarding inheritance, Philosophy Zoologique, “runs fully 405 pages in its English translation yet it contains only two sentences specifically about giraffes”.Thus, the historical and scientific significance of this specific example as a characterization of Lamarck’s thought appears to be greatly exaggerated.
Also, in judging the validity of Lamarck’s theories, there is the issue of what was known and knowable in Lamarck’s time. As Hugh Samuel Roger Elliott writes in his introduction to Philosophie Zoologique, at the time of Lamarck “many of the known facts of evolution might be accounted for either by use-inheritance or by natural selection. If it is true that acquired characteristic are hereditary, then the giraffe might well have developed his neck through that agency. The hypothesis fits the facts.” However, Elliot goes on to also note that “but so also does the hypothesis of special creation,” and also that “similarly, again, natural selection is equally satisfactory as an a priori hypothesis.” In other words, for Lamarck and those of his time, “the facts are covered by at least three different and mutually exclusive hypotheses,” and without the benefit of a posteriori experiments, for example, Lamarck opted for the a priori validity of use-inheritance. What was required next, Elliott observes, was to verify empirically the mechanisms for such inheritances, which neither Lamarck nor anyone else of his time pursued. Still, concludes Elliot, given the specific circumstances of Lamarck “few indeed are the people who are competent to judge of the correct use of deduction in difficult biological inquiries”.
Given the march of history, Lamarck’s choice now appears clearly as the incorrect choice. There are a couple of reasons for this, in particular Lamarck’s a priori method of reasoning combined with his philosophical orientation–neither of which are or should be considered indicative of contemporary epigenetics. As Michael Ghiselin writes:
Lamarck’s approach to evolution was that of a metaphysician rather than a natural scientist. It invoked a mystical assumption (the notion that organisms sought “perfection” and tended to become increasingly complex and man-like) which could not be treated scientifically and could not be supported or contravened by evidence. For that very reason, Lamarck’s construct was not a proper theory and was not at all comparable to the theory that Darwin would later present in On the Origin of Species. Darwin’s concept was a well articulated body of scientific thought that could be, and was, tested by recourse to facts. Lamarck’s was not.
In other words, making scientific comparisons between Lamarck and Darwin is like making a scientific comparison between…Deepak Chopra and Stephen Jay Gould, which is as fair to Chopra as it is to Lamarck, and as equally unfair to contemporary epigenetics.
Now, while Ghiselin’s point is not to defend Lamarck’s theories of inheritance per se, but rather to demonstrate that “the Lamarck presented in schoolbooks, however, is a fiction — an imaginary figure who has been fashioned from hearsay and wrong guesses, and who has been replicated in countless books by successive teams of plagiarists”, my point is to show to what extent the juxtapositions of Lamarckism against Darwinism as a demonstration of the invalidity of non-selectionist theories of evolution and development are little more than crude straw man arguments. As ‘Lamarckism’ is so often used as an epithet against contemporary epigenetics, as a shorthand means to discount the validity of its claims, I hope the preceding shows just how much Lamarckism as such does not apply to contemporary findings like epigenetic inheritance, and therefore should not be used to try and invalidate such science-based claims.
Still, for a while, Lamarckism competed with Darwinism (Darwin himself actually proposed Lamarck-esque mechanisms for the transmission of acquired traits which Darwin called “pangenesis”). However, this Lamarckian “soft inheritance” is now generally dismissed as a quaint pre-Mendelian theory of evolution in lieu of the Modern Synthesis which locates the source of adaptation exclusively in the random mutations of genes. Again, though, even if actual Lamarckism is seriously flawed (which it likely is), this actually has little significance for contemporary epigenetics. However, that Lamarckism as such has been so unilaterally and uncritically and unfairly applied as an invective against epigenetics is, I think, of substantial significance.
The scientific rationale for the rejection of Lamarckian inheritance is largely provided by experiments such as August Weissmann’s tests of whether mutilations of parents (e.g., cutting off the tails of rats) could be passed on to their offspring, and the transplantation of guinea pig ovaries by Castle and Phillips in 1911, which appeared to verify empirically that adaptations of such characteristics were not inheritable. Even though these experimental protocols did not accurately reflect the mechanisms of inheritance as theorized by Lamarck, the results of these experiments were taken as definitive disproof of the possibility of the inheritance of acquired characteristics. (In other words, in this case as well misinterpretations of Lamarck’s theories are used as evidence of the validity of gene-focused selection-based theories which isolate our biological essences from our environments, and the invalidity of alternative explanations which closely link these essences with our environments.) From these experiments was postulated Weismann’s Barrier, a tissue barrier between those cells involved in forming the body of an organism (somatic) and those cells involved in sexual reproduction (germinal). This barrier allegedly protects the germ cells from any type of environmentally-induced change, which therefore prevents Lamarckian inheritance.
Of particular interest at this point, though, is Hugh Samuel Roger Elliott’s observation that, as of 1914, Weissmann’s postulation of this barrier against use-inheritance was as pure and as dangerous a deduction as was Lamarck’s a priori support for use-inheritance:
But while we remain in our present ignorance as to the causes of development, and of the extraordinary and specific influence which the pituitary, thyroid, reproductive and other glands exert upon remote parts of the body, and indeed of many other remarkable correlations existing between apparently disconnected parts, our empirical knowledge is surely far too slight to offer any kind of firm basis for a large reaching deduction like that of Weissmann.
In other words, for all the experiments of Weismann, the results did not of themselves justify the blanket denial of use-inheritance as such, but still needed further verification as to the mechanisms involved; all that Weismann was able to show was that the mutilation of parents was not inherited by the offspring. Subsequent research has supported the presence of Weissman’s Barrier, but the actual mechanisms of this Barrier are even just now being identified. The recency of these verifications suggests that other mechanisms which operate outside of Weissman’s Barrier may yet be discovered, and there is suggestive evidence that these other epigenetic mechanisms are also being found. In the comments to this post, Abhay Sharma has provided links to recent research that demonstrates the mechanisms of the transmission of information from the soma to germline in plants and mammals.
I suggest that there are underlying ethical and political reasons for the acceptance of the provisional findings of Weissman and the others which fit the emerging paradigm of isolated essences. These early choices as to which line of research to pursue necessarily influenced the subsequent development of the theory. Further discussion of these underlying motivations will be conducted in subsequent posts, but the specific historical trajectory of the development of the Modern Synthesis and of conventional genetics, with the exclusion of epigenetic inheritance, is an important point to keep in mind.
In the 1950s the theoretical importance of this isolation of our biological essences from our environments is revealed again when Francis Crick and James Watson asserted the “central dogma of molecular biology” that DNA is also insulated from the vagaries of the environment. According to the central dogma, “the chemical language of genetic information in the form of DNA sequences can be directly copied into complementary nucleic acid base sequences termed RNA which in turn can then be translated into a protein sequence of amino acids, a quite different chemical language”. This chemical language is noncommutative, though, which means that “genetic information never flows in reverse from a sequence string of amino acids into a complementary sequence of DNA or RNA bases”. In other words, DNA is not influenced by its environments, which means there is no adaptation of DNA, and that genetic variation only happens randomly. Thus, barring very rare and random—i.e., accidental and uncontrollable—genetic mutations, each person is born with a pristine normal copy of the human genome.
This assumed isolation of our biological essences—although arrived at through scientific processes—is a central tenet of the modern theory of genetics. However, this insulation of our essences from our environments also has significant, though often overlooked, ethical implications, especially in light of this blanket and facile (and now highly suspect) dismissal of all non-selectionist theories through comparison with Lamarckism. The motivations behind these comparisons with Lamarckism are one way history, philosophy and ethics enter the ostensibly exclusive scientific domain of genetics. The elaboration of these ethical implications will be the focus of subsequent posts, such as Epigenetics and the Extended Synthesis and The Genetics of the Ethics of the Science of Genetics.
Why has this fundamental misconstrual of Lamarck played such a significant role in the dismissal of epigenetics, if not at least in part for political and/or ethical reasons? I am curious to hear what you think. Leave your comments below and I will respond.
For further discussion of the convergence of politics and science around Lamarck’s time, see also The History of Epigenetics and the Science of Social Progress. For discussion of the politics and science of epigenetics in the 20th century, read A Brief History of Epigenetics: C.H. Waddington, Epigenetics and the Dustbin of History and Epigenetics and the geopolitical history of the 20th century.
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Moore, J. N. 1970. Biology: a search for order in complexity. Grand Rapids: Zondervan Pub. House.
 Lamarck, Jean-Baptiste.  2011. Zoological Philosophy: An Exposition with Regard to the Natural History of Animals. Cambridge: Cambridge University Press, xlii.
 Geison, G. L. (1969). “Darwin and heredity: The evolution of his hypothesis of pangenesis”. J Hist Med Allied Sci XXIV (4): 375–411.
 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.
 E.J. Steele. 1999. Lamarck’s Signature : How Retrogenes Are Changing Darwin’s Natural Selection Paradigm. Basic Books.
 Lamarck, Jean-Baptiste.  2011. Zoological Philosophy: An Exposition with Regard to the Natural History of Animals. Cambridge: Cambridge University Press, xliv.
 Solana, J. (2013). Closing the circle of germline and stem cells: the Primordial Stem Cell hypothesis. EvoDevo, 4(1), 1-17.
 Sharma, A. (2013). Transgenerational epigenetic inheritance: focus on soma to germline information transfer. Progress in biophysics and molecular biology,113(3), 439-446.
 Francis Crick. 1970. “Central Dogma of Molecular Biology.” Nature 227(5258):561-3.
 E.J. Steele. 2000. “The Evidence for Lamarck.” Quadrant 364(44): 47-56.
 E.J. Steele. 2000. “The Evidence for Lamarck.” Quadrant 364(44): 47-56.