Evolution Writ Small

One might think that the natural place to look for an understanding adequate to the evolutionary history of life would be the powers of self-transformation we observe in the evolving organisms themselves. But it can be dangerous to look in a clear-eyed manner at the creative potentials of living beings. One risks having to acknowledge the evident wisdom and agency so vividly on display. In an era of institutionalized materialism, any suggestion that these inner powers are vital to the entire evolutionary story can only produce the sort of discomfort associated with a taboo.

On the other hand, Stephen Jay Gould ran afoul of no taboo when he effectively ascribed this same wisdom and agency to natural selection. Countering the questions we heard voiced in Chapter 16 about what sort of creative principle could explain the “arrival of the fittest”, he asked (referring to several giants of twentieth-century evolutionary biology), “Why was natural selection compared to a composer by Dobzhansky; to a poet by Simpson; to a sculptor by Mayr; and to, of all people, Mr. Shakespeare by Julian Huxley?”

The answer, Gould said, is that the allusions to poetry, musical composition, and sculpture helpfully underscore the “creativity of natural selection”:

The essence of Darwinism lies in its claim that natural selection creates the fit. Variation is ubiquitous and random in direction. It supplies the raw material only. Natural selection directs the course of evolutionary change. It preserves favorable variants and builds fitness gradually.¹

On its face, this argument for Darwinism was a puzzling one. Its answer to the question how variation arises amounted to saying nothing more than “It is everywhere” (“variation is ubiquitous”) — which, one might have thought, only added urgency to the need for an explanation. The suggestion seems to be that, because organisms are so expert and prolific at producing new possibilities of life, the evolutionist can simply take their powers of achievement for granted without actually looking at them. Because organisms so abundantly provide what is needed (“raw materials”) for the transformation of life, we are somehow free to declare natural selection the transforming agent. It need only preserve all those wonderfully effective new variants, and they will somehow integrate themselves into the almost infinitely differentiated unity of a living being. We need not concern ourselves with those powers of integration and unity. After all, what could they have to do with evolution?

How easy it is, apparently, to forget that the so-called “raw materials” being preserved are never merely raw materials! At the first appearance of any substantive change, the creative work has already been accomplished — if indeed the change is truly beneficial to a living being. We find ourselves looking, not at random raw materials, but at a whole harmoniously transforming itself as a whole, where everything tends to affect everything else.

In this way, whatever we may have falsely isolated in our minds as a “new feature” is incorporated into the tightly interwoven complexity of an organism’s life. The only power we know to be capable of such incorporation is that of the organism telling its own story, a story always reflecting the qualitative, unified character and dynamic developmental potentials of a particular species.

This harmonious incorporation of new features, founded upon whole-cell inheritance and manifested in whole-organism processes of development, is where we see creative evolutionary change originating. The spreading of an already-existing change through a population is an entirely different matter.

So Gould’s response shows us that one of the evolutionist’s strategies for coping with taboo agency is immediately to turn the question, “How does creative change arise?” into the different question, “How does creative change, once arisen, spread through a population?” The switch of topics is not hidden, but occurs in plain sight. Only a habit of blindsight relative to the organism’s agency seems able to explain such an obvious evasion of a real biological question.

None of this means we need to doubt whatever is true in the idea of natural selection (which may be very little that bears directly on evolution). Selective mortality certainly occurs throughout all domains of life. Not every organism lives out a full life. But the mere elimination of problematic traits (or defective organisms) through mortality is not the same thing as positively and viably transforming the integral unity that a particular organism is.

The point is not terribly subtle. There is simply nothing in the idea of natural selection itself that points to the creative capacities necessary for producing new adaptive features — for producing, say, a four-chambered heart (with all its organism-wide implications) from a three-chambered one. There is only the living being whose agency and activity natural selection necessarily assumes and which evolutionists have unconsciously transferred to a mystical “mechanism” of selection somehow operated by the inanimate world.

So, if we do not accept this subterfuge, we are left with the main question for this chapter: What do organisms show us, directly, compellingly, and uncontroversially, about their own powers of organic transformation? Much of the first half of this book contributes to an answer, especially at the physiological and molecular levels of observation. But in the present, evolutionary context, it will be well to look at the organism from a new angle.

As researchers hone their ability to investigate single cells, they are finding that even neighboring cells, “identical” in type and occupying the same tissue or niche, reveal great heterogeneity. Every cell is, in whatever degree, “doing its own thing”.

Strikingly, however, the cell is not only doing its own thing; it is also heeding the “voice” of the surrounding context, which is in turn an expression of the unity of a particular kind of organism. So each cell is disciplined by the needs of its immediate cellular neighborhood as well as those of the entire developing organism, which in turn is conditioned by the larger environment. Every organism — even a single-celled one — is a remarkable diversity within an overall, integral unity.

In humans there are, for example, cells (neurons) that send out extensions of themselves up to a meter or more in length, while being efficient at passing electrical pulses through the body. There are contractile cells that give us our muscle power. There are the crystalline-transparent fiber cells of the lens of the eye; their special proteins must last a lifetime because the nucleus and some other subcellular entities (prerequisites for protein production) are discarded when the fibers reach maturity. There are cells that become hard as bone; as easily replaceable as skin; as permeable as the endothelial cells lining capillaries; and as delicately sensitive as the various hair cells extending into the fluids of the inner ear, where they play a role in our hearing, balance, and spatial orientation.

Many of these cells are as visibly and functionally different, in their own way, as the phenotypes of any two organisms known to us. This, you might think, would interest the evolutionary biologist. It has drawn the attention of a few who — if they do venture to comment about it — tend to be widely ignored on the point. One such is the much-awarded biochemist, cell biologist, and cancer researcher, Mina Bissell, who remarked in an interview with Cell magazine, “Your nose and mouth are completely different and yet they have the same DNA. So what on earth is telling the DNA what to do?” (Bissell 2020).

The question is as old as it is decisive. A hundred years ago, as we heard in Chapter 7 (“Epigenetics: A Brief Introduction”), the pre-eminent biologist, Frank Lillie, who served as president of the National Academy of Sciences, said that “those who desire to make genetics the basis of physiology of development will have to explain how an unchanging complex [DNA] can direct the course of an ordered developmental stream” (Lillie 1927, pp. 367-68). I can’t say there’s much evidence yet that evolutionary biologists feel they should bother with the question.

A gamete is at least as specialized as any other cell of the body. At the same time, this gamete, along with the entire lineage leading up to it, must retain the potential to yield the totipotent zygote. That is, despite its commitment to a highly specialized, reproductive function unlike that of any other cell type in the body, the germline cell must at the same time preserve within itself the flexibility and freedom that will be required for its role as progenitor for every cellular lineage of a new organism.

It is an extraordinary mandate, and our bodies must focus extraordinary powers of development upon it. For example, the chromosomes of both sperm and egg will have been modified by epigenetic “marks” (Chapter 7, “Epigenetics: A Brief Introduction”), ensuring that certain genes in the offspring will be active, or repressed, depending on which parent the gene was inherited from. Other widespread marks imposed by the parents will (for the most part) be erased immediately after fertilization. This leaves space for the new organism to structure the spatial, electrical, and chemical characteristics of its chromosomes (and therefore also its gene expression) according to its own way of being and developmental potentials.

And, of course, there is the elaborately orchestrated “meiotic ballet” (Page and Hawley 2003) that produces both sperm and egg, each with only half the number of chromosomes found in somatic cells, and with those chromosomes reshuffled and otherwise modified according to a logic and via activities that are still largely beyond any comprehensive understanding. But one thing is sure: the body’s rearrangement (“recombination”) of its germ-cell chromosomes during meiosis is now showing itself to be highly regulated. Multiple protein complexes and epigenetic modifications of chromosomes function combinatorially, with synergism, antagonism, and redundancy: “The new-found multiplicity, functional redundancy and [evolutionary] conservation” of these regulatory factors “constitute a paradigm shift with broad implications” (Wahls and Davidson 2012).

So we are given no choice but to think of the germline as an expression of that same agency — that same, end-directed transformative power — through which our bodies subtly, elaborately, and adaptively direct each of their other cell lineages toward a distinctive form and functioning within the unity of the whole. We have seen that this power of transformation comes to intense expression in entire differentiating cells, quite apart from any mutations in their DNA. And it is just a fact that an entire cell is what each parent passes on as an inheritance to its offspring.

It would be strange indeed if the organism’s ability to proceed adaptively and creatively along paths of whole-cell developmental transformation were to become frozen at the very point where, via the most sophisticated activity imaginable, it prepares its whole-cell bequest for the next generation. Can we reasonably claim that this is the one cell lineage in which the organism’s normal, future-oriented activity goes silent? Or that, with all the organism’s expertise at producing and stably maintaining diverse phenotypes even without changes in DNA sequence, it “refuses” to employ this expertise when it comes to the preparation of inheritances? Or that the power with which the organism adapts all its cells, tissues, and organs as far as possible to new or unexpected conditions is a power lost to it in the management of its own germline?

If every organism is a living agent and power of becoming, as we know it to be, then surely that power of agency — whatever its nature, and however conditioned and constrained by the material results of its previous activity — is the decisive thing preparing the way for a new life. And yet our science has not even addressed the problem of this species-specific formative power, let alone asked about its source or about what role its unfolding expression and its development of its own potentials might play in evolution.

The questions we do ask — and ask compulsively — have to do with how an organism’s genes mutate, not how, say, a mammal directs its single, inherited genome toward the radically different fates of a lens cell and a liver cell. Such cellular fates (not unlike the whole-organism fates of larva and beetle or tadpole and frog we also discussed above) are repeatedly and stably achieved before our eyes and with apparently casual ease, despite their being more complexly divergent over the space of a few weeks or months than the changes accomplished in a million years within many an evolutionary lineage.³

Another question we could wonder about is how all this creative potential of the organism bears upon the question of genetic mutation itself. And here we would have to reckon with the same future-oriented aspect we see in every cellular lineage during an organism’s development, and indeed in all biological activity. Which is to say that the real question hasn’t yet even been posed.

That question is not “How does a mutation affect this organism’s fitness”, but rather “How does it relate to where the species is going evolutionarily?” It cannot be emphasized enough that this latter question differs radically from that of fitness. After all, a tadpole in the process of transforming into a frog — having lost its tadpole organs for feeding and digestion, but not yet having completed the formation of the corresponding frog organs — is presumably not as fit as the fully mature frog. But this temporary “unfitness” is exactly what is required for the sake of the future.

Notes

1. Gould 1976. By the time Gould completed his 2002 masterwork, The Structure of Evolutionary Theory, he would offer a richly nuanced qualification of these statements. But his fundamental belief in the creative role of natural selection — or, as he would say, its “efficacy” — remained.

2. Goliath beetle larva and adult photo credit: Frantisek Bacovsky.

3. The organism’s ability to transform its cells (that is, to transform itself) independently of genetic mutations during development becomes especially significant when we consider those evolutionary lineages where change seems to occur at an unexpected, almost preternaturally rapid pace. See, for example, the discussion of cichlid fish evolution in the lake region of East Africa (Chapter 19, “Development Writ Large”). But we would expect germline DNA, over generations, to be caught up in a species’ self-transformation, just as are all other available resources. The main point is that DNA would not be the sole or leading factor in the change. It would, in its own way and like all the other parts, express the evolving whole, not govern it.

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Steve Talbott :: Evolution Writ Small