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Darwin’s Revolution

Nothing produced more resistance to Darwin and his supporters than the claim that human beings had themselves evolved from “lower” forms of life. By an ironic inversion, nothing has titillated public interest in evolution in our own time so much as the search for the bones of human ancestors. The surest way to intense, if fleeting, fame and glory is to announce that some tooth, jaw, skullcap, or entire head has just been dug up that is “probably a human ancestor.” If it is a half-million years older than the oldest “probable human ancestor” already known, fame and controversy are guaranteed.

There is a problem, however. The only way to be sure that a fossil is really a human ancestor is to find one that is already indubitably human, but then it has no interest. The farther back in time one goes and the greater the differences from us, the more likely it is that the bones belong to some twenty-second cousin twelve times removed. During the last hundred years, there has been a gradual change in the understanding of paleontologists about the shape of evolutionary trees. At one time it was thought that a group of related fossils of increasing ages could be aligned in a single ancestral order or, at most, two or three branches joining the main stem at a few points. It is now reasonably clear that most fossils of different ages cannot be connected in a linear sequence, but represent a small sample from a lot of parallel lines. Evolutionary trees have become bushes. Since fossils, especially of vertebrates, are few and far apart there are big gaps in the fossil record, and any temptation to arrange fossils in a linear order is likely to be overturned when the next bone is dug up. Often a supposed ancestor will turn out to be contemporaneous or even later than the species to which it supposedly gave rise. Between two million and one million years ago there were four known coeval “apemen,” including three that probably used tools.

What makes the situation all the more confused is that the shapes of organisms do not change uniformly in time. There are periods of rapid change and periods of relative stasis. That observation has led to the theory of “punctuated equilibrium,” which exaggerates and universalizes that temporal irregularity. According to punctuationists, gaps in the fossil record are real and are the consequence of long periods of absolutely no change in organisms followed by a paltry few thousand years of very rapid evolution. Gradualists, who scornfully refer to this theory as “punc. eq.,” say that it is just hard to find the intermediates because suitable fossil-bearing strata are so seldom exposed, so what appears as “punc. eq.” is just punk rock.

The theory of punctuated equilibrium is applied to the human fossil record in Eldredge and Tattersall’s The Myths of Human Evolution. The authors are judicious but biased, minimizing the observed differences between fossils so that they can claim that species show no significant change over a million years or more. There just is not enough material evidence to make a convincing case for punctuated equilibrium from human fossils, but one thing is clear from their analysis. The search for the missing link, the oldest form that is clearly in the direct line of human ancestry, is a delusion. No one knows, or ever will know with the sort of evidence upon which we now depend, whether any fossils is a direct ancestor of the people who dig them up and write books about them. That will not stop the claims. One doesn’t get many column inches with the announcement that yet another bit of yet another relative of unknown degree has been found in the deserts of East Africa.

Despite the myth of song and story, we did not descend from monkeys or apes, at least not from any forms of them now alive. But we did have common ancestors with chimpanzees and gorillas, not all that long ago. Just how long ago, and who among the living apes is our nearest relative, is not known for certain.

The Monkey Puzzle by Gribbin and Cherfas makes a convincing, if breezy argument, accessible to a lay reader not frightened by an occasional number, that we are as closely related to the sulky gorilla as to the lovable chimp, and that our genes parted company from theirs only about four to five million years ago. The evidence comes from a form of nonadaptive evolution that has turned out to be one of the most powerful tools biologists have in reconstructing ancestry. It appears that some of the building blocks, the amino acids, of which some of our proteins are made, can be replaced with blocks of slightly different molecular form without affecting the function of the proteins. As the generations succeed one another, this replacement occurs at a clocklike rate, independent of natural selection for specific adaptation. If this clock can be calibrated, by counting the number of replacements that separate two species whose time of evolutionary divergence is known form the fossil record, even approximately, then for other species without a fossil record a time of divergence can be estimated. It is this technique that has shown us to be a mere five million years separated from Mr. Jiggs.

Unfortunately, Gribbin and Cherfas seem to think that this information tells us something important about the human condition. After all, they say, our proteins are only I percent different from those of apes. But this is a spurious comparison. The authors have forgotten, in their anxiety to say something profound, that the very method they describe with such clarity depends critically on protein differences that have no functional significance in the first place. If calibration of the molecular clock uses nonadaptive evolutionary change as its basis, then how can they expect to draw adaptive meaning from the amount of that change? More generally, how do we convert the percentage difference in molecular composition into a percentage difference in shape, size, or the ability to do biochemistry? I would turn the comparison upside down and remark how little difference in protein structure can correspond to such profound differences in organism. It is a sign of the foolishness into which an unreflective reductionism can lead us that we seriously argue from protein similarity to political similarity.

While they are more relevant to proteins than to politics, Darwin’s writings have a great deal more in common with those other grand theorists of the nineteenth century, Marx and Freud, than with, say, Newton. Darwin’s work is filled with ambiguities, contradictions, and theoretical revisions. The early Darwin of the Beagle in 1836 is neither the middle Darwin of the preliminary sketch of 1844 nor the mature Darwin of The Origin in 1859. Indeed, successive editions of The Origin contain important changes, and at one point Darwin seriously flirted with the inheritance of acquired characteristics, a notion that is logically fatal to his entire enterprise.

So, like the other Victorian radicals, Darwin has become the subject of a major historical industry. His letters, his diaries, his notebooks, his successive sketches, editions, and papers are the fossil bones to be used by the paleontologist of history in building a true picture of the beast. Unlike the remains of long-dead animals, however, the Darwinian fossil record is very unlikely to become fuller. Barring the discovery of a dusty bundle in some unlit corner of the Royal Society’s attic, we have it all, and historians must be content to find the real Darwin by rereading and reinterpreting the same words. For me at least, the reconstruction has remained something of a cardboard cutout of a Great Man, eccentrically hypochondriacal, but indubitably a great man, unlike any practicing scientist I have ever known.

Barry Gale has changed all that. I do not know whether his thesis in Evolution Without Evidence that Darwin published The Origin of Species without confidence in his evidence, and well before he intended to, is right or wrong. Certainly Gale has produced an abundance of quotations that support this view. As late as February 1858, Darwin wrote to Hooker, “I must come to some definite conclusion whether or not entirely to give up the ghost [of my theory],” and six months later wrote to Asa Gray at Harvard, “I cannot give you facts and I must write dogmatically, though I do not feel so on any point.” But in a corpus as rich as the Darwin letters and notebooks, there are quotations to prove anything. What is appealing in Gale’s work is a picture of a life in the social community of science that corresponds to our everyday experience of how careers are built.

Darwin returned from the voyage of the Beagle in 1836 to become a rising young star in geology. He was ambitious, courted success and successful men, and cared for their approval. He wrote in his autobiography (a genre not usually entered into by the self-effacing) that he wanted a “fair place among scientific men.” When, after ten years, he had exhausted the career possibilities of geology, he turned his full attention to biology, including, among other questions, what was universally acknowledged to be the problem of the time. For twenty years he successfully exploited his relationships with the community of biologists to acquire information and specimens and to stake out a long-term claim on the species problem.

That is why it was to him that Alfred Russel Wallace wrote in 1858 with the news of his own independent invention of the theory of natural selection. Darwin was already a member of the British scientific establishment (he had received the Royal Medal of the Royal Society two years before), so it was to other establishment figures that he turned for tactical advice on how to save his scientific priority while saving his soul. He rather hoped the problem might go away since Wallace had not actually said he was hoping for publication, but Darwin’s friends did not take the hint, and the solution agreed upon was a joint publication. So, it appears, Darwin was hustled into publication before he was really ready, for otherwise, as he put it, “all my originality, whatever it may amount to, will be smashed,” and “it seems hard on me that I should be thus compelled to lose my priority of many years standing.”8

It is not only ambiguity, contradiction, and long intellectual development that Darwin shared with other nineteenth-century revolutionaries. They are all dimly perceived through slogans. Survival of the fittest, like penis envy, is the opium of the people, To understand Darwinism simultaneously as a social phenomenon arising out of the remaking of the British social structure and as an extraordinary insight into the operation of natural forces, requires considerable knowledge and subtlety of mind. To explain all that clearly, correctly, wittily, but without condescension, to a lay public demands a high expository art. What one obviously needs for the job is to put together a physician-director-actor-comedian-TV star with the illustrator of Swamp Comix. It has been tried, and it works. While the illustrations are at times a bit swampier than the text demands, Darwin for Beginners is a superb introduction to a very tricky subject. It puts all the emphasis in the right place, is historically correct, scientifically impeccable, and contains as a postscript the best 250 word piece on reductionist social explanation yet written. Anyone who reads and understands Jonathan Miller’s text will know a good deal more about Darwinism than most biologists and historians, while the pictures will be a constant reminder not to take the life of the mind more seriously than it deserves.

What is the revolution that Darwin made? It was not the idea of evolution. Nor was it the invention of natural selection as an explanation. Although undoubtedly ingenious, and certainly a correct characterization of a great deal of evolution it is, in the end, only a completion of the unfinished Cartesian revolution that demanded a mechanical model for all living processes. Nor was it even the variational model for a historical process in place of the usual transformational scheme. The invention of the variational model was indeed a considerable intellectual feat and represented a real epistemological break, for it changed the locus of historical action from the individual to the ensemble. Collectivities, the species, changed even though each individual within them was constant through its lifetime. What the variational model does is to convert one quality of variation, the static variation among objects in space, into another quality the dynamic variation in time. As extraordinary as that insight may be, it can hardly be said to revolutionize, by itself, our way of seeing nature. It remains, again, a mechanism.

Darwin’s real revolution consisted in the epistemological reorientation that had to occur before the variational mechanism could even be formulated. It was a change in the object of study from the average or modal properties of groups to the variation between individuals within them. That is, variation itself is the proper object of biological study, for it is the ground of biological being. Without it, there would have been no evolution and therefore no living biological world, for the earliest proto-life would have long since made the world uninhabitable for its own kind.

Before Darwin, the central issue for science was to discover the Platonic form that lay behind the imperfect reality, as Newton in the first book of the Principia treated ideal bodies moving in perfect voids, and only later considered the disturbing effects of friction and viscosity. Variation among organisms was thought to be ontologically distinct from the causes of their similarity, a similarity that we glimpse but dimly. If only we could eliminate the noisy confusion of the material objects themselves, the true relation would be seen. Darwin revolutionized our study of nature by taking the actual variation among actual things as central to the reality, not as an annoying and irrelevant disturbance to be wished away.

That revolution is not yet completed. Biology remains in many ways obdurately Platonic. Developmental biologists are so fascinated with how an egg turns into a chicken that they have ignored the critical fact that every egg turns into a different chicken and that each chicken’s right side is different in an unpredictable way from its left. Neurobiologists want to know how the brain works, but they don’t say whose brain. Presumably when you have seen one brain you have seen them all. Given the extraordinary complexity of connections in a brain, it is at least conceivable, if not likely, that two people may organize their memories of the same event differently, or, God forbid, differently on different days of the week. Even my $100 home computer reorganizes and moves its memory storage around as I add more input. Geneticists, who are supposed to know better, will sometimes talk about a gene’s determining a particular shape, size, or behavior instead of reminding themselves that if genes determine anything, it is the pattern of variation of a developing organism in response to variation in the environment.

This error of geneticists is particularly ironic, because it was Gregor Mendel who, unknown to the rest of the scientific world, had, contemporaneously with Darwin, solved the other leading problem of biology by making variation his object of study. Mendel solved the problem of why offspring look like their parents by studying the pattern of differences between them. He discovered, as Darwin had, that similarity and variation are inextricably intertwined aspects of the same reality.

  1. 8

    Letters to Charles Lyell, June 18 (the day he received Wallace’s letter) and June 26, 1858.

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