Epigenesis in relation to evolutionary phenomena

According to Piaget:

"... biologists today, like Julian Huxley and Waddington with their "synthetic theory" of species, are making phylogenesis depend in part on ontogenesis, and not only the inverse. Indeed genes are not actually static elements but, rather factors identical or analogous to enzymes, whose nature is revealed by their activity, interdependently and subject to a whole set of regulations throughout the entire process of embryogenetic growth in interaction with the environment. The result of this is that the information supplied by the genotype is not only transmitted but also transformed in the course of all this development, so that the essential system is no longer the genotype in isolation but a total ‘epigenetic system’."⁷

Thus, even on the genetical level, the notions of interactionism and constructivism - which Piaget considers characteristic of epistemological activity in general - are thought to apply. Instead of treating the genotype in isolation - which had been the tendency of classical mutationsits - and as something mysteriously removed from the observable phenotypic variations in a given race or species, modern genetics construed the collection of genotypes as a relational totality or genetic system (known as a genome) in which there were genes capable of performing different, but complementary, functions of a structural and regulatory nature.

In other words, some of the genes were of the traditional sort, so to speak, and conveyed or transmitted structural information concerning such things as the physiological or morphological properties of different biological dimensions of a given organism. On the other hand, there were other genes which were concerned with regulating the organizational properties of the genetic system as a whole - both in terms of the way structural genes transmit their information, as well as in terms of the way in which the genetic system responds to, and interacts with, the environment. Considered as a whole, structural and regulatory genes represent a series of processes that encompass a range of qualities (such as transmission, variation, deep structure and surface structures) said to be characteristic of genetic phenomena.

In addition to conceiving of the hereditary mechanism as a dynamic, interacting totality, Piaget also describes how there is a growing tendency - to which he subscribes - in modern biology, when considering the issue of the basic genetic unit, to switch the emphasis, or focus, from the genome to the genetic pool or population.

Attendant to this switch in focus, from the genotype to the genetic pool, there is also a change in emphasis concerning the "reaction norm". The ‘reaction norm’ refers to the set of possible phenotypes that can be generated from a genotype - given variations in the environment to which the genotype responds by way of altering the genetic system (either in a structural or regulatory manner) such that phenotypic variations subsequently appear. With the aforementioned change in emphasis and focus in certain facets of biological investigation, the notion of "reaction norm" (while still appropriate and meaningful in the context of individual genotypes) also came to be used as a way of referring to the set of phenotypic possibilities represented by the mixture of genotypes existing in any given population.

Seen from the perspective of the interaction of genomes and population, evolution consists of the complex series of transformations that occur on two levels - each of which affects the other level. These levels are: (1) the responses of the individual genotype to the surrounding environment - which itself represents a contribution to the genetic pool; (2) the responses of the population as a whole to the surrounding environment, which includes the influence of a variety of structural and regulatory possibilities generated internally by individual genotypic reaction norms within the population.

Moreover, just as there is a set of equilibration principles which co-ordinate the activity of the genome or collection of genotypic possibilities within the hereditary mechanism of a given organism, so too, according to Piaget, there is a set of organizational principles that are auto-regulatory in nature with respect to the genetic pool as a whole. For Piaget, this set of organizational principles represents both the source, as well as the result, of evolution in general. (e.g., see his discussion on pages 278-284 in Biology and Knowledge).

Using the genome/genetic pool interactionist approach outlined above, Piaget plans to analyze what he considers to be the three possible ways for theoretically accounting - in evolutionary terms - for the relationship between organism and environment. These three ways are:

"(1) environment takes control of the organism and molds it throughout its working existence, affecting even its hereditary structures, which easily submit to its influence;

"or (2) it is the organism that imposes certain independent hereditary structures on the environment, the environment merely eliminating such structures as prove unsuitable or nourishing those it finds congenial;

"or (3) there are interactions between organism and environment such that both factors remain on an equal footing of cooperation and importance."⁸

However, since Piaget is primarily interested in establishing the biological underpinnings of epistemological processes, he also needs to draw up a corresponding set of possibilities with respect to the sorts of biological structures and functions (which, presumably, can be accounted for by one, or more, of the three foregoing theoretical frameworks) in which knowledge can be rooted. Thus:

"There are, in effect, three possible kinds of knowledge: (1) the kind that is linked with hereditary mechanisms (instinct, perception), which may or may not exist in man but which correspond in biological terms to the sphere of characteristics transmitted by the genome; (2) knowledge born of experience, which thus corresponds in biology to phenotypic accommodation; and (3) the logico-mathematical kind of knowledge which is brought about by operational co-ordinations (functions, etc.) and corresponds, in biology, to regulation systems of any scale..."⁹

However, before Piaget discusses these kinds of knowledge, he wants to lay the foundations for them by demonstrating how an epigenetic approach can provide a tenable means of accounting for evolutionary development . If successful, then, epigenetic principles also might serve as a prototypic example, in general, for explaining a large variety of transformational processes - including the transition from organic structures and functions to cognitive systems.

When Piaget mentions evolutionary theory in the context of the sort of organism/environment relationships that can be construed in terms of the environment's taking control of the organism, he, generally, has in mind: (a) Lamarck's (or a Lamarckian-like) theory in which the exercise of various organs during the course of development influenced the direction and nature of such development; (b) the way in which the changes brought about by the exercising of organs during development were fixed in hereditary as acquired characteristics; and, (c) the manner in which the environment - in terms of its physical properties - forced or selected the exercising of particular organs that led to the fixing of such hereditary characteristics.

For Lamarck, the biological organism was, largely, a passive or malleable entity that was molded according to the nature of the influences and pressures existing in the different features of the immediate environment and the effect such forces had on various organs in a given organism. Although Piaget does acknowledge the importance of the role played by the environment in modifying the hereditary mechanism and credits Lamarck for having seen its significance in the evolutionary context, he nonetheless criticizes Lamarck for, among other things, having overestimated the passivity (or having underestimated the activity) of the biological organism in bringing about evolutionary change - which is to say, that even though the organism is influenced by external influences, such influences are assimilated to various action schemata that exist prior to the organism's present encounter with the environment.

Furthermore, Piaget notes that on the basis of Lamarck's emphasis on the organism's supposed passivity, one would tend to expect the organism to be malleable to an indefinite extent according to the direction and nature of the environmental factor which was affecting the modification in, say, a given organ's functioning. Yet, nowhere, according to Piaget, does one see evidence of such malleability.

Instead, one finds that, generally speaking, the limit situation with respect to malleability is a function of the reaction norm that is, it is a function of the range of phenotypic possibilities associated with both the individual genotype as well as the population consisting of mixed genotypes. Consequently, as far as Piaget is concerned:

"... what is lacking in the Lamarckian interpretation is the explicit recognition of the fact that the effects of these exercises (i.e., of the organs) are always relative, not only to the environment, but to the genotypic structure (pure or impure) of the lineages being studied. To sum up, where Lamarck sees nothing but the effect of environment... there are really interactions between external factors and the genome."¹⁰

At the opposite extreme from the Lamarckian penchant for emphasizing the significance of the environment in effecting evolutionary change, is the tendency of those theorists who play up the importance of an organism's endogenous factors in bringing about such change. For Piaget, the most notable of such theories is the mutationist school of thought.

According to this approach to evolution, genotypes are generally considered to be static or invariable hereditary structures except in instances in which variations (due to certain factors internal to the organism) in these structures are introduced on a, supposedly, random basis. The term for such variations is, naturally, mutation.

Moreover, the classical mutationists contend that the role of environment as an evolutionary agent is after the fact and, consequently, has no real evolutionary significance. In other words, since evolutionary change is a function of random variations or mutations and the role of the environment is restricted to a post facto selection of certain of these variations which it favors, evolutionary transformation per se is, in the mutationist conception, unrelated to environmental considerations and dependent only on the random variations.

One objection Piaget has to the mutationist position is that such a theory tends to treat the hereditary mechanism in an atomistic fashion. Thus, genes are considered to be so many separate boxes that open up only on those occasions when it releases a new mutation which its internal processes have mysteriously produced and immediately thereafter seals itself off from external influences.

This atomistic conception of the gene effectively isolates the gene from all possibility of interaction with the environment. As a result, one neglects the considerable evidence compiled by Waddington, Julian Huxley and others concerning the complex relationship between genome and environment that is said, by such investigators, to be responsible for evolutionary change.

Moreover, the mutationist view is in considerable contrast to the cybernetic features which Piaget has argued are characteristic of biological phenomena on every level - from the hereditary to the cognitive. Therefore, for Piaget, the mutationist position appears strangely inconsistent with what seems to be a persistent feature of biological activity in general.

In addition to the foregoing sorts of objections to the mutationist position, Piaget cites another kind of argument. much later in Biology and Knowledge during a discussion of instinctual phenomena. Piaget argues:

"But if it is not considered in any way incompatible with survival that evolution should wait some thousands of centuries to endow a horse with a tail and a mare made of hairs and not feathers, it becomes rather difficult to envisage how long it would take to ingrain the instincts of reproduction, nest-building, and so on among species whose very existence depends on cognitive precision in relation to those instinctive mechanisms. We need only take one example the eye in vertebrates'.¹¹This is not indispensable as a means of acquiring knowledge but it is indubitably useful. Bleuler's calculations showed that if the mutations necessary for the formation of this organ had been brought about simultaneously or co-jointly, they would have had a probability of only 1 in 10¹², in other words, practically none. On the other hand, if it had been a question of successive mutations, in which new ones were simply added to preceding mutations so that a cumulative effect was achieved, then it would have taken as many generations as would correspond to the age of the world or even exceed it."¹³

Of course, Piaget acknowledges that such calculations are dependent on a number of variables (such as the age of the' earth, rates of mutation, population sizes, and so on) that have¹⁴been assigned numerical values based on a certain amount of approximation and guess work. However, even if one were to dramatically readjust the calculations in the direction of estimations more favorable to the mutationist position'' (which may not be at all justifiable except in a logically heuristic sense) and, thereby, reduced the probability to, say, 1 in 10¹⁵, one is still talking about a very, very small probability.

While one might be willing to admit the logical, and even empirical, possibility of such a small probability of occurrence becoming a reality on occasion, the boundaries of credulity are distorted beyond recognition or reasonableness at the suggestion that numerous events of such small probability should have happened with such frequency. Indeed, seemingly, one is forced to seriously consider the possibility that such a combination of happy coincidences might be the result of operative factors other than random mutations.

Any position that arrives at a conclusion contrary to the foregoing appears to be demanding that the individual take a great deal on faith. To believe that such a series of random coincidences occurred on a regular basis appears to be a rather far-fetched exploitation of the notion of logical possibility, and, as such, is far removed from any kind of empirical evidence capable of pointing to its 'likelihood' or plausibility.

7. Ibid., p 81.[Back to Text]

8. Ibid., p 99.[Back to Text]

9. Ibid., p 100.[Back to Text]

10. Ibid., p 106.[Back to Text]

11. Ibid., pp 273-274.[Back to Text]

12. Ibid., p 279.[Back to Text]

13. Ibid.[Back to Text]

14. Piaget discusses, in several places in Biology and Knowledge, the idea of population genetics (e.g., see pp. 277-285). Following a trend in certain areas of biological research, Piaget develops the view that population and individual are interdependently involved with each other (although Piaget tends to attribute a greater importance to population over individual; see top of page 281) in interchanges concerning genetic information - information that is ultimately a function of the populations's and individual responses (usually of a sort that seeks to re-establish equilibrium) to tensions in the environment. In this regard, he speaks of hereditary modifications through a "probability of action" involving all possible crossings in the population's genetic pool and which is drawn upon as the population's response (and, therefore, the individual's response) to the different tensions produced by the environment.

In my opinion, however, the whole population genetics movement is seriously misguided to the extent it attempts to supplant the individual in favor of the population. The possibilities inherent in the population are little more than what is given to it by the individuals of the population in both a negative and positive sense - "negative" referring to the limitations which are inherent in a given species and "positive" referring to the flexibility and scope of possibilities inherent in the species.

In either case, it remains to be seen how the population, per se, can generate anything new that was not already inherent in the contributions of the various individuals to the genetic pool. Mutations may cause the appearance of something new but mutations appear, on the one hand, independent of the population concept and, on the other hand, mutations only can bring about a change in terms of acting upon the givens and, therefore, the change is going to be functionally related to, and not independent of, what it acts upon.

In short, the population cannot produce something totally outside the structures on which it works. Population is limited to the possibilities of modification at hand which are defined by the nature of the potential inherent in the organisms which give expression to the population.[Back to Text]

15. Natural selection does not determine what chance events in an organism will generate. Natural selection only reinforces, as it were, those chance mutations that are' capable of surviving in the given environment to which the notion of natural selection gives expression.