Lamarck’s Actual Lamarckism (or How Contemporary Epigenetics is not Lamarckian)

Excerpt from my forthcoming book Epigenetics and Public Policy The Tangled Web of Science and Politics to be released April 2018 by Praeger

Policymakers are going to be increasingly confronted with issues involving epigenetics in any number of domains. In these confrontations, epigenetics is going to be presented in different ways, through different narratives, according to the political agendas of the different groups involved. If recent history serves as a reasonable guide to the future, a reasonable assumption is that the policy narratives promoted by groups which are opposed to epigenetics (e.g., because epigenetics research has produced a result with which they disagree or which is damaging to their position) will often describe epigenetics as Lamarckian. This designation of contemporary epigenetics as Lamarckian is usually intended to portray epigenetics as either anti-Darwinian, or anti-genetics, or simply as unsubstantiated pseudo-science.

For policymakers and those interested in the public policy process to make adequately informed decisions about epigenetics, the nature of this description of epigenetics as Lamarckian needs to contextualized properly. While there are aspects of Lamarckism and contemporary epigenetics which do pertain to each other, there are substantial differences between them. Contemporary epigenetics is also not inconsistent with Darwinian natural selection, and is properly a subset of conventional genetics. Thus, the guilt-by-association intended by this association of epigenetics with Lamarckism is both misleading and not an accurate description of either. Understanding the differences between the two will also make it that much easier to see the political motivations which underlie such characterizations of epigenetics.

Lamarck and the giraffes

A quick demonstration of how Lamarck and Lamarckism are often misconstrued, is the classic example used to describe Lamarckian inheritance of the elongation of giraffe necks as a result of giraffes having to stretch to reach available forage located higher and higher in the trees. The theory for this elongation that is so often attributed to Lamarck is that the physical effects from the constant stretching of the necks by giraffes in one generation was then passed on to their offspring in the next generation as slightly longer necks. Giraffes in these subsequent generations were then able to reach a little higher into the trees, which again 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.[1]

However, it bears mentioning that this prototypical example was not a central aspect of Lamarck’s theoretical exposition of the mechanisms of inheritance. Although Lamarck did advocate for use-inheritance in evolution, the historical and scientific significance of this specific example as a characterization of Lamarck’s thought appears to be greatly exaggerated.  As observed 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.”[2] Granted, pointing out the prevalence of this specific example of the giraffe may not be a definitive or convincing defense of Lamarckism per se, it is at least illustrative of the widespread mischaracterization of the theories of Lamarck.

The true theory of inheritance of Lamarck

Lamarck’s actual theory of biological inheritance, for which he is supposedly so famous or infamous, and against which contemporary epigenetics is so often compared, is elaborated in his master work Philosophie zoologique ou exposition des considérations relatives à l’histoire naturelle des animaux (Zoological Philosophy: Exposition with Regard to the Natural History of Animals) published in 1809. In this book Lamarck proposed two rules or laws in particular which together constituted the first systematic theory of biological evolution: the law of use and disuse of organs, and the law of the inheritance of acquired characteristics:

  1. Use-disuse: In any animal that has not passed its time of development, the more frequent and sustained use of any organ gradually strengthens, increases and develops this organ during this use; while the constant lack of use of such an organ imperceptibly weakens and deteriorates it, gradually diminishing its faculties, until eventually it disappears.
  2. Inheritance of acquired characteristics: All that nature has caused to be acquired or lost by individuals through the predominant use or constant lack of use of such an organ because of the influence of circumstances in which their species has been exposed for a long time is preserved by nature through the generation of new individuals, provided that the acquired changes are common to both sexes [via sexual reproduction], or to those who produced these new individuals [via asexual reproduction].

The second rule, the inheritance of acquired characteristics, is what Lamarck is most known for today, and is what prompts most of the usually derisive comparisons of contemporary epigenetics with Lamarckism. However, there are a couple of very significant aspects of both laws within Lamarck’s original theory which are relevant for understanding the nature of the comparisons of epigenetics with Lamarckism, and for situating epigenetics within the general thrust of conventional evolutionary theory and genetics.

Again, as Stephen Jay Gould points out in his encyclopedic history of evolutionary theory[3], the second law in Lamarck’s theory was not particularly innovative, even for his time. Instead, his first rule, about the use and disuse of organs and body parts as the mechanism for the acquisition of novel characteristics, was Lamarck’s “revolutionary statement” and “one of the great transforming insights in the history of human thought.”[4] Lamarck’s connecting changes in environment and behavior with changes in form is what transforms his theory of inheritance into a revolutionary theory of evolution.

As such, and in what has particular relevance for discussions of genetics and epigenetics today, for Lamarck organisms were not passive tablets onto which environmental influences were carved, but rather changes in the environment provoked changes in behavior which over time resulted in changes in form, which functional changes in morphology were then passed on to offspring. To quote Lamarck at length from Philosophie zoologique:

Whatever the environment may do, it does not work any direct modification whatever in the shape and organization of animals. But great alterations in the environment of animals leads to great alterations in their needs, and these alterations in their needs necessarily lead to others in their activities. Now if the new need becomes permanent, the animals then adopt new habits which last as long as the needs which invoke them.[5]

As Gould points out, this aspect of Lamarck’s theory of evolution is actually quite Darwinian in many fundamental ways, but appears fifty years before Darwin. There are definite differences between the two theories of evolution in the identified mechanisms of change—altered habits establishing new selection pressures for Darwin but inducing heritable changes in morphology for Lamarck—but, at this level at least, both theories occupy the “common ground of functionalism,” just expressing different versions of the same deeper commitment, according to Gould.[6]

What truly distinguishes Lamarck’s actual Lamarckism from Darwinism is therefore not their different theories of inheritance, per se, although this is generally the reason given for comparing epigenetics with Lamarckism, and for subsequently discounting epigenetics. In fact, Darwin even explicitly includes Lamarckian use-disuse inheritance in his account of natural selection, as detailed by Ernst Mayr, one of the architects of the Modern Synthesis:

Curiously few evolutionists have noted that, in addition to natural selection, Darwin admits use and disuse as an important evolutionary mechanism. In this he is perfectly clear. For instance…on page 137 he says that the reduced size of the eyes in moles and other burrowing mammals is “probably due to gradual reduction from disuse, but aided perhaps by natural selection.” In the case of cave animals, when speaking of the loss of eyes he says, “I attribute their loss wholly to disuse” (p. 137). On page 455 he begins unequivocally, “At whatever period of life disuse or selection reduces an organ…” The importance he gives to use or disuse is indicated by the frequency with which he invokes this agent of evolution in the Origin. I find references on pages 11, 43, 134, 135, 136, 137, 447, 454, 455, 472, 479, and 480. (Mayr, E. (1964/1859). “Introduction.” In Charles Darwin On the Origin of Species: a Facsimile of the First Edition. Harvard University Press.)

Instead, according to Gould, the real differences between these theories, and the main reasons for which Lamarck was castigated in his time, were Lamarck’s assertions that evolution was a progressive process of the perfection of organisms, and that life continuously arises from a process of spontaneous generation.

The first of these, Lamarck’s emphasis on evolution as a process of gradual perfection, arose from his own strong commitment to uniformitarianism and gradualism. For Lamarck, because climate and geology only changed continuously and gradually so also must organic evolution be continuous and gradual, but always tending towards greater complexity as more adaptations accrue, culminating in the biological perfection that is humans. This emphasis on the uniformity and gradualness of change is actually what provoked the ire of Lamarck’s most fierce and powerful scientific opponent, Georges Cuvier, often referred to as the ‘Father of Paleontology’, who lauded Lamarck for his anatomical work on invertebrates but excoriated him for his promotion of uniformitarianism (in lieu of the catastrophism which Cuvier endorsed).

The second of these, the proposition of the continuous and spontaneous chemical generation of life at its simplest undifferentiated forms, was Lamarck’s attempt to rebut the question that if evolution was a continual process of complexification, then why were there still organisms with the simplest anatomies? In answer to this question, Lamarck proposed that organic life arose spontaneously from the decomposed chemical residue of more complex organisms which had died. These undifferentiated primal forms were then carved from within by the motions of fluids motivated by a ‘force of life’ leading to the emergence of distinct organisms. In Philosophie zoologique, Lamarck clearly asserts that the functioning of this life-force in spontaneous generation “which induces a corresponding variety in the shapes and structures of animals” was causally distinct from the process of adaptation in response to the environment.[7]

Thus, Lamarck ultimately bases his theory of evolution on two sets of forces: the causal force of the external environment to impel adaptation, and internal forces of differentiation. Of his two proposed forces in evolution, the external and the internal, Lamarck in his time was discounted and denigrated much more for his emphasis on these internal processes of adaptation, both for the antiquated, pre-Lavoisian chemistry he relied upon to explain it and the unexplainable vitalism he expounded as a central component of it. Very few of his contemporary detractors took exception—or as much exception—to his description of the inheritance of acquired characteristics, which, as Gould explains, actually exhibits strong affinities with Darwin’s own theories of inheritance.

Regardless, and notably, today it is Lamarck’s theory of inheritance that is generally painted as being proven wrong on its face by Darwin. This brush is then used to smear contemporary epigenetics as also conflicting with Darwinism and the accepted theory of evolution, and therefore as also necessarily wrong on its face. That epigenetics is so often portrayed as Lamarckian, even though these characterizations of both epigenetics and Lamarckism are factually incorrect, is a telling indicator that the underlying motivations for this ascription are often other than scientific.

[1] Moore, J. N. 1970. Biology: a search for order in complexity. Grand Rapids: Zondervan Pub. House.

[2] Roizen, R. (1971). “The Argument of  Philosophy Zoologique.” http://www.roizen.com/ron/Lamarck.htm.

[3] Gould, S. J. (2002). The structure of evolutionary theory. Harvard University Press.

[4] Ibid. p. 179.

[5] Lamarck, J. B. P. A. (1809/2011). Zoological philosophy: an exposition with regard to the natural history of animals. Hugh Samuel Roger Elliott (Trans.) Cambridge University Press, p. 107.

[6] Gould, S. J. (2002). The structure of evolutionary theory. Harvard University Press, p.179.

[7] Lamarck, J. B. P. A. (1809/2011). Zoological philosophy: an exposition with regard to the natural history of animals. Hugh Samuel Roger Elliott (Trans.) Cambridge University Press, p. 112.

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