Inheritance and the Whole Organism

In 1923 Wilhelm Johannsen, the Danish plant physiologist and pioneering geneticist who had earlier given biologists the word “gene”, expressed concern about the way genes were being conceived as neat, cleanly separable causal units. He made the following curious remark, which remains today as intriguing as ever, despite its never having prompted much serious discussion within the field of genetics as a whole:

Personally I believe in a great central ‘something’ as yet not divisible into separate factors. The pomace-flies in Morgan’s splendid experiments continue to be pomace flies even if they lose all “good” genes necessary for a normal fly-life, or if they be possessed with all the “bad” genes, detrimental to the welfare of this little friend of the geneticists (Johannsen 1923, p. 137).

The pomace-fly, of course, was the fruit fly (Drosophila melanogaster) that Thomas Hunt Morgan, in his Princeton University laboratory, was famously converting into a “model organism” for genetic studies. Thanks to procedures for mutating genes, controlling the mating of the flies, and tracing the inheritance of traits, this was the fateful period during which “genetic” was becoming synonymous with “heritable”. The fact that whole cells — and not merely genes — pass between generations was progressively losing its significance in the minds of biologists interested in inheritance and evolution. They could, after all, now see cause and effect displayed in the relation between mutated segments of chromosomes and changes in eye color or defective body parts.

Johannsen realized that this new genetic work was based on the assumed existence of separate and independent causes of traits, and therefore left untouched what might easily be seen as the central problem of inheritance: the faithful reproduction of kind, or type — that is, the maintenance of the integral unity that harmonizes all the particular traits and parts of an organism and expresses that organism’s characteristic way of being. While mutated genes might result in (typically pathological) differences in certain narrowly conceived traits, this sort of change never reached through to the fundamental identity of the organism. Whatever the introduced variations (mutations), the pomace-flies always remained pomace-flies.

Johannsen’s problem arises because we can hardly help recognizing the distinctive unity of a living being — a unity we have difficulty equating to any particular parts. Rather, the organism seems in some way responsible for its parts. We never see an organism being constructed or assembled from already-existing parts. In its development it works to bring them about — to differentiate them out of a prior unity. Every organism is the power to do this work, and the power is not derivable from its results. If some of its parts become deformed, the organism works out of its unity to compensate for the deformities, doing so according to the way of being of its own kind.

But what sort of genetically investigated differences was Johannsen dismissing as disconnected from the problem of the whole? In his brilliant, and still decisively relevant¹ 1930 book, The Interpretation of Development and Heredity, the British marine biologist E. S. Russell took up Johannsen’s concern. “When we say that a child shows a hereditary likeness to its father”, Russell wrote, “we mean that it resembles its father more closely than it does the average of the population. The likeness is observable in respect of those [rather incidental] individual characteristics that distinguish the father from the rest of the race” (emphasis added). Much the same can be said of the child’s resemblance to its mother.

It’s also possible that there will be no particular resemblance to either parent. “But yet in all three cases the child would show the characteristics of its species and its race — it would be a human child, distinguishable as belonging to the same racial type as its parents”. As Russell then noted, this general resemblance in type, whereby all members of a species share an entire manner of development and way of being, can hardly be understood by referring to the inheritance of this or that inessential variation wherein a parent happens to differ from most other members of the species. But such inessential variations have been a main focus of geneticists’ investigations for the past century.

The distinction between a fundamental, shared nature, on one hand, and individual peculiarities that occur within that shared nature, on the other, has practical implications for genetic research:

The broad general resemblances of type give no hold for experimental or statistical treatment, and have accordingly on the whole been ignored. But it is this general hereditary resemblance which constitutes the main problem. [The gene theory] deals only with differences between closely allied forms, and with the modes of inheritance of these differences; it leaves the main problem quite untouched as to why, for example, from a pair of Drosophila only Drosophila arise. It takes for granted the inheritance of Johannsen’s “great central something” — the general hereditary equipment of the species (Russell 1930, pp. 269-70).

We could also add here that the species’ capacity to produce variations in offspring was drastically understated by the methods the researchers employed — a problem that continues to this day. These laboratory methods, by keeping conditions as uniform as possible, enabled geneticists to isolate more or less reliably reproducible “causes”. This strengthened their conviction that biological causation could be approached on the model of the physical sciences. In other words, the experiments were designed, perhaps unintentionally, so as to reinforce pre-existing beliefs about the nature of biological causation. After all, without reliable, unambiguous, isolated causes and effects, how could one come up with a publishable paper?

What this overlooks is that every organism is a thoroughly holistic (contextual) being whose entire business might be seen as the continual redefining of its own part-relations, or causal interactions, in response to different environments. Keeping those environments constant in the laboratory was a way of repressing the full expression of the organism’s character as it might have manifested under varying circumstances — a unity that could not be summed up in terms of a set of discrete and fixed causes and effects.

A vast (and almost overwhelming) amount of research today has had to be aimed at elucidating the context-dependent activity of organisms that was overlooked earlier. As a result, “context-dependent” is now a byword of genetic and molecular biological investigations (Chapter 6). And yet the pathological tendency of the earlier work, compulsively driven as it was by the effort to isolate unambiguous causes, continues to distort these newer investigations (Chapter 9).

You might think that, given the broad fact of infertility between different types, biologists would have cast around for new approaches to the problem of an organism’s inherent governing nature, even if it required quite different methods from those they were trained in. (See Chapter 12 for examples of alternative methods.) What is at stake, after all, is our understanding, not only of the organism, but also of evolution. We certainly cannot answer all the questions we have about fundamental evolutionary change — for example, questions relating to the origin of basic body plans — merely by looking at how specific gene variants correlate with differences between closely allied forms of the same general type.

The picture I have been developing in this book shows us that organisms are in fact coherent, qualitative, story-telling wholes that inform and define their own parts. The parts, being so informed, share in each other’s identity and become inseparable features of a larger unity. Some such picture has been acknowledged by many biologists throughout the history of their discipline. If the picture is accurate, then the power to maintain this larger unity across generations — which also suggests a power to transform the unity — would seem to be central to our understanding of heredity and evolutionary change.

This is truly decisive. Have biologists in our day lost sight of the whole organism because of their fixation upon the molecular parts known as genes? And have they lost sight of evolutionary dynamics because of their fixation upon the hereditary transmission of genes rather than entire living cells?

Russell laid direct hold of this matter when he considered what it meant to realize that the activity of an organism cannot be reduced to the actions of its individual parts. If it is truly the case that the organism as a whole plays a governing role whereby it continually informs its parts with its own character and “catches them up” within its own powers of activity, then the performance of the whole “can be [hereditarily] transmitted only by a whole, i.e. by the egg in its entirety, which already at the very beginning of development is the new individual” (Russell 1930, p. 283).

Russell then cited a 1903 comment by the German botanist F. Noll (who was writing before the word “gene” came into usage):

If the egg-cell of a lime tree is already a young lime tree, there is no need of any idioplasm, germ-plasm, pangens, or heredity-substance to render possible its development into a lime tree; the egg-cell as a whole is the heredity-substance (Russell 1930, pp. 287-88).

Amid this diversifying whirl of cell lineages in a human embryo, where our genomes are simultaneously being summoned into the service of wildly different cellular phenotypes, we can hardly help asking: What is the unifying and coordinating source, or power, through which all the radically diverse differentiating cells are formed into coherent tissues, organs, organ systems, and the stable, functional unity of an entire human being?

To get a grip on the organizational challenge, think first of the “humble” yet extremely dynamic and context-sensitive “hair follicle niche” we looked at in Chapter 6. Then consider the unthinkable number of distinct niches, many of them microscopically small, in the liver, or in the kidney, or in the brain, pancreas, bone marrow, and every other part of the body. They are all extraordinarily complex. Vast numbers of such interpenetrating contexts, while mutually shaping each other, must somehow come under a global coordinating power reflecting the form and life of one human being.

The interactions within and between all these niches, organs, and organ systems look as though they are virtually infinite. Furthermore, environmental conditions and bodily activity are continually changing in an endlessly varying manner. As a result, those “virtually infinite” interactions, including the patterns of gene usage in billions of cells, are only momentary. They must be capable of being reorganized minute by minute and hour by hour.

Further, the task of global coordination goes far beyond what we normally think of as coordination. For the parts being coordinated are always in the process of becoming more or less different parts. We are never speaking merely about the coordination of existing parts, but also about their transformation — and, ultimately, their coming into, or passing out of, existence.

Is all this not one angle from which to view Johannsen’s “great central something”? Yet, a century after his comment few have gained the courage to contemplate this coordinating/creating power so evident in every organism, let alone to ask about its relation to inheritance. For example, regarding the wise and living capacities through which the unity of the organism is sustained, and through which the materials of inheritance are caught up into a gamete: do we not have every right to question whether these capacities can themselves be accounted for by the materials that take form through their agency?

That may seem a strange question. But there is nothing wrong with acknowledging the constrictive boundaries of our current understanding. At present we scarcely know how to speak about such matters. But we shouldn’t have difficulty at least holding on to the observationally sound idea of the unity, wholeness, and distinctive character of every organism. Only by starting with what we observe can we work toward a deeper understanding. And one thing I believe we can say is this: the wholeness and character of an organism is most fully visible in its powers of directive activity, not in the material results of this activity.

On the face of it, the failure of biologists to explore the powerful explanatory potentials of the organism’s more-than-genetic, whole-cell capacity for directed change seems to reflect one of the most egregious and crippling blockages of thought in all the history of science. You may recall the question put forward in Chapter 17 when we were looking at cell differentiation: Why should a forward-looking, adaptive power, manifest in all organic activity and vividly demonstrated in all the cell lineages of our bodies, cease altogether at just one decisive point: namely, the point where the germ cell lineage contributes a gamete to the next generation?³

If anyone is appealing to mysticism or magic, presumably it is those who posit such an otherwise unexplained hiatus in the organism’s routine management of its differentiating cells. These all participate in the organism’s power to move directively toward a future state that is not at all rigidly determined by its current state. It is clear that every cell, every embryo, and (as the paleontological record so strongly suggests) every population of organisms possesses a nature that not only reflects its material past, but also contains its own characteristic potentials for adaptive self-transformation.⁴

Think of it this way: if an organism is so thoroughly holistic that changing any one thing will change many other things, then (on the gene-centered/mutational view) evolution in the direction of greater overall fitness would require a virtually impossible combination of beneficial mutations to different parts of the organism all at once, so that they might all be selected together.⁵ Such seems to be the prevailing view, anyway.

Lewontin’s “quasi-independent” criterion has been picked up by others, sometimes in order to make jabs against the idea of holism. Philosopher of biology Kim Sterelny, for example, has written that “It is hard to change developmental sequences if the development of any characteristic is linked to the development of many characteristics. For a change is likely to ramify, having many effects on the developed phenotype, and some of these are nearly certain to be deleterious”:

Thus, to the extent that development is holistic, the more complex the organism, and the more it has been elaborated over evolutionary time, the less significant further change there can be in that lineage. The point that adaptive change would be impossible if development were holistic has been made before. Lewontin, for example, has pointed out that such change requires traits to be “quasi-independent” … (Sterelny 2001).

But there is something strange here. This argument from Lewontin and Sterelny emerges from the assumption that evolution is rooted in genetic mutations that are more or less random, and therefore likely to conflict with one another. In other words, it is rooted in an assumption that the organism does not function integrally, coherently, and holistically. Then the argument is turned against the idea of holism that has already been denied by assumption. That’s not much of an argument.

If an organism’s life and development is holistic in the manner that has so long been recognized, why should we suddenly lose sight of this holism as soon as we turn our attention to its implications for evolution and inheritance?

Why, for example, should we abandon our faith in an organism’s holistic capacities when it comes to the preparation of a coherent inheritance for its offspring? And why should we lose sight of the developing organism’s remarkable capacity to integrate and reconcile as far as possible its various physical resources — or, for that matter, the even more stunning capacity of two gametes to organize their separate lineage inheritances (each containing many “mutations” relative to the other) into a single, viable zygote?

It seems that the very idea of holism is so alien to biologists that the attempt to think it is aborted before it gets very far. This is all the more odd given that many of those repelled by the idea of holism in general are also (and with justification) enamored of the inescapably holistic idea of phenotypic plasticity — the organism’s ability to alter itself in order to adapt to a particular environment. If organisms are phenotypically plastic, then their different internal systems — for example, those involved in bone growth, muscle growth, and nerve growth — must be tightly integrated, so that they can respond adaptively and mutually to changes in each other. “Phenotypic plasticity”, we read in one enthusiastic author, “pre-adapts lineages to evolutionary change, by connecting the development of distinct organ systems”:

Limb development requires simultaneous and co-ordinated development in other organs and tissue systems: cartilage, muscle tissue and attachment points, innervation of soft tissues; circulatory connections to tissues and bone marrow. If bone structure or muscle mass is plastic, responding to signals from the environment, co-ordinated systems must be plastic too, responding to signals from the systems developing with them … This same sensitivity of integration to the contingencies of development will make functional integration possible in the face of genetically-caused changes in crucial organ systems.

The author of these remarks (Sterelny 2009) happens also to be the author of the comment above about the problem holism presents for evolutionary change. It’s as though, when one’s attention turns to evolution, one is obligated to begin thinking of change as if it were brought about, not by the character and agency of the organism, but by random disturbances to a mere aggregate of particulate genes that somehow map to and determine the organism’s phenotype.

And, yes, it is then very hard to imagine a set of scattershot changes that would, in harmony, alter the intricately interwoven, holistic way of being of an organism. But once we have acknowledged an organism’s holistic nature — and, in particular, its capacity for holistic, adaptive change — why should we so quickly forget it, especially when, in evolutionary theory, we are actually addressing the issue of holism?

Perhaps Sterelny changed his mind between the writing of those two articles. In any case, I am not here saying anything about the degree of “quasi-independence” some organismal traits might have. Nor am I suggesting that evolution is equally possible for all species. For all we know, physically evident evolution may no longer be occurring in humans — or not occurring nearly as much as in previous evolutionary eras. It might be argued, after all, that in humans a major evolutionary transition is placing the power to direct evolution into our own hands. And this looks more like an evolution of consciousness than a further bodily evolution.⁶

As for “quasi-independent” traits and holism, I think Samuel Taylor Coleridge, writing during the first half of the nineteenth century, put the question into the right perspective:

“The living power will be most intense in that individual which, as a whole, has the greatest number of integral parts presupposed in it; when moreover, these integral parts, together with a proportional increase of their interdependence, as parts, have themselves most the character of wholes in the sphere occupied by them” (Coleridge 1848).

Or, re-phrased: Life will be fullest in the individual that most fully integrates the greatest number of parts; and when those parts are themselves most like wholes. We can glimpse the unity underlying these apparently contrary principles when we realize how, in human society, an ever stronger and more centered self is required if we want that self to contribute ever more strongly and selflessly to the good of the larger society.

Or think of your heart or brain. These wonderfully “perfected” organs, while possessing the strongest possible identity and wholeness in their own right, are — as an expression and extension of their wholeness — bound together with everything else that goes on in the body. No part of our bodies can be separated from the circulatory and nervous systems, just as the functioning of the heart and the brain cannot be separated from the other parts of our bodies.

In other words, the potential for holism and the potential for a (relatively) independent perfection of parts are two sides of the same coin. An overall, deeper holism depends on a greater independence and perfection of parts in their own right, and a greater independence and perfection of parts depends on a deeper holism. The two principles do not push in opposite directions, but are complementary, with each requiring the other.

Coleridge’s remark derived, I believe, from a straightforward observation of living beings and required no evolutionary theorizing. He was, of course, writing before Darwin’s Origin. And he was willing to look at whole organisms as they actually presented themselves. There is nothing in evolution that contradicts the most profound holism of organic life, which is in turn what makes evolution possible.

Notes

1. On the relevance of Russell’s work today, see “Heredity, Development and Evolution: The Unmodern Synthesis of E. S. Russell” by Maurizio Esposito (2013). For a view of Russell along with W. E. Ritter, Kurt Goldstein, Agnes Arber, and J. H. Woodger, see “A Reflection on Biological Thought: Whatever Happened to the Organism?” by Robin W. Bruce (2014).

2. Hybridization does in fact sometimes occur between distinctly different species (within limits) and, as I mentioned in Chapter 19, it is possible that this contributes to rather dramatic evolutionary change. But such hybridization is likely to generate massive genetic and cellular reorganization, far too extensive and global to allow for conventional genetic approaches. So one is still facing the unsolved “problem of the whole” — the problem that genetic analyses were designed to steer clear of by focusing on particular genes causing particular trait differences under well-defined conditions.

3. Evolutionists are interested in germline (heritable) genetic mutations as the primary basis for evolutionary change. Yet no one will quarrel with the fact that we lack any such germline mutational basis for the very great changes that can occur in the differentiating cell lineages of a complex, multicellular organism. But some biologists do reasonably ask whether there are non-germline (“somatic”) mutations along the various paths of cellular differentiation, and whether these play some role in the processes of differentiation. The question is being actively explored today.

Even before the matter is elucidated, however, we can say this much: to whatever degree somatic mutations do occur and are important to cell differentiation, the fact would show only that the organism manages and directs its own genetic mutations. Why? Because cell differentiation (and development in general) are such obviously directive processes, and are universally recognized as such. If mutations turn out to be an essential part of these processes, it will show that they do not play their roles in a random manner, but rather find their place within the larger coordinated activity.

4. I have never heard an evolutionary biologist even acknowledge the possible legitimacy of an inquiry into the heritable, whole-cell, transformative capacity of germ cells or gametes. They certainly do not seem inclined to cite evidence for anything of the kind, or even to pay much attention to the fact that the development and specialization of the germ cell lineage is at least as dramatic and well-directed as the differentiation of any other forward-looking cell lineage in complex organisms (and all differentiating cell lineages are forward-looking).

But, just as important, the claim of “no evidence” for more-than-genetic, whole-cell inheritance, when it is made, usually reveals itself as spectacularly circular, being based on the argument that, whatever the whole-cell transformation we witness in germ cell lineages, we don’t see corresponding changes in the genetic sequence. That’s the argument that surfaces so often when the question of transgenerational epigenetic inheritance is raised. In other words, an insistent assumption that all heritable change must take the form of germline genetic mutations — or at least be closely analogous to them — is being used to refute the claim that there is more-than-genetic, whole-cell, heritable change. (See Chapter 22, for a discussion of the curious idea that evolutionary change depends on the stability — unchanging nature — of already achieved mutations.)

When confronted with the problem of the character of the whole cell, biologists have a tendency to cite the impossibility of carrying out their usual analyses wherever one insists on speaking of “wholes”. (See the immediately following section.) And so there has never been a major research program aimed at tracking how whole-cell inheritance might play into evolution. The most obvious possibility is the least considered — not because it is faulty, but only because it is difficult.

5. See Lewontin 1978 and Levins and Lewontin 1985. In the latter work the authors wrote:

By quasi-independence we mean that there exists a large variety of paths by which a given character may change; although some of these paths may give rise to countervailing changes in other organs and in other aspects of the ecological relations of the organism, in a reasonable proportion of cases the countervailing effects will not be of sufficient magnitude to overcome the increase in fitness from the adaptation. In genetic terms, quasi-independence means that a variety of mutations may occur, all with the same effect on the primary character but with different effects on other characters, and that some set of these changes will not be at a net disadvantage (p.80).

6. German philosopher, Dieter Wandschneider, has commented that “In a world in which sickness can effectively be cured, clinics and spas are at people’s disposal, artificial limbs are applied, and replacement organs are implanted, the biological principle of [Darwin, in its modern form] has been ‘unhinged’”:

One could object that the human species changes biologically even today — for example, in muscle structure, susceptibility to sickness, and life span. That cannot be denied. But these changes are manifestations of the “self-domestication” of man and thus consequences of civilization, which as such are not the results of natural selection. On the contrary, they are expressions of an evolution that is now taking place under completely different conditions, namely those of cultural evolution (Wandschneider 2005, p. 204).

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Steve Talbott :: Inheritance and the Whole Organism