AND THAT'S HOW THE ELEPHANT GOT HIS SPOTS

Dear Mr. Darwin: Letters on the Evolution of Life and Human Nature, 39-46 (Gabriel Dover, Univ. of Cal. Press, Los Angeles, 2000)

The question of the origin of adaptations is not a simple one to answer. First of all, as I explained in earlier correspondence, your process of natural selection and its final product have been given the same name: adaptation. This is unfortunate in that cause and effect are terminologically locked together, leading to the easy belief, prevalent in many quarters, that if a given function can be described as an adaptation (for example, wings for flying) then it must have arisen through natural selection. The proof of the pudding of selection is taken to be in the description of the function as an adaptation. With few exceptions there is no concern for the real weakness of natural selection theory, which is its ability to account for too much. Sir Peter Medawar, an eminent man of science and British Novel laureate, expressed this succinctly when he reflected that “natural selection has such an enormous experimental facility that one could hardly imagine anything it could not explain. Now the danger of this is that it rules out any incentive to enquire about any other possible mechanism that could explain the observed facts.”

The reason for the universal acceptance of natural selection as a mechanism for the origin of diverse forms of life is that it is based on the simple fact that some but not all diverse life forms have survived. That some forms of life exist and continue to survive in particular environments whereas others have not is incontestable. If the evolutionary process of adapting to particular environments is defined as one of differential survival, and the mechanism responsible for this process is defined similarly by differential survival, then no further independent proof is required of the system other than that given by the formal definitions. Those that survived are by definition better adapted to the environmental circumstances that ensure their survival. So differential survival, measured in terms of relative number of offspring populating the next generation, becomes synonymous with the concept of adaptation. This being so, we are left with an explanation of the diversity of life as a consequence of an ever-increasing radiation of life forms adapted to new environments under the aegis of natural selection. Everything is for the best in this best of all possible worlds, and all existing components of form and behavior have their adaptive utility. Survival and adaptation are often merged in a warm fog of wishful and more-or-less tacit equivalence. . . .

Despite the fact that this problem of tautology is an old and hoary chestnut, it has not been satisfactorily answered. We can go round and round the problem but never quite break out of the circle, although I attempted to do as much in my very first letter. Indeed, the ease with which we take refuse in the circle is endearing. I cannot resist giving one homely example to drive the point home.

Recently a British television award was given for the best wildlife film of the year: a documentary on the seasonal change in environment and life around a single water-hole in the Namibian desert. We are entertained by life in the raw. No sooner are our sentiments aroused by the lovable antics of one animal than it disappears, whole or in part, down the gullet of another. Nature red in tooth and claw under the strong Namibian sun. All appealed to the magic of natural selection as sole provider of the adaptive wonders required for survival in the unfriendly and inhospitable surroundings. One such wonder lies in the shape of the abnormally large ears of the bat-eared fox. This creature is of normal fox proportions except for its bat-like ears. The voice-over blandly proffered the explanation that such extremities have evolved by natural selection for greater efficiency in aural tracking of subterranean prey. The bat-eared fox, accepting its cue, obligingly inclines its ears to the ground. There could be no doubt that such ears are of great utility in this pursuit, just as there could be no doubt in the mind of the commentator as to the reason for their evolution. The present-day use of these particular ears is taken as prima facie evidence their evolution as an adaptive device that increased the survival of past generations of animals that possessed them. The force of Sir Peter’s warnings is no more apt than in this commonplace extrapolation from current usage to past evolutionary change. Why are professional biologists willing to accept this line of reasoning? . . .

Just-so story telling

Why are so many evolutionary biologists convinced of the unshakable truth of the overarching relationship between novel biological functions and origins as adaptations produced by natural selection? The fault line goes back to Mendel. As I wrote earlier, his rules of inheritance led to the realization that without natural selection there could be no change in the frequencies of different versions of the gene in a populations. As natural selection was the only known process in the 1930s that could handle the spread of novel genes and produce ever more refined adaptations, it is not surprising that all functional novelties are believed to be circumscribed by this process. We might not actually know what happened during the evolutionary history of the giraffe’s neck, but until recently we have had no cause to question that it arose by natural selection, for natural selection is all that there was.

All we need do, if we are so inclined, is to tell the most plausible ‘just-so’ stories about the significance of ever-longer necks in the lineage leading to giraffes. For many years, longer necks were considered to have evolved in response to the urgency of reaching leaves high on the trees. More recently, the story has changed to one in which the adaptive superiority of longer necks is in response to sexual prowess between sparring males. No matter what the story of the decade might be, our school textbooks are certain in their description of how the giraffe got its long neck – solely through the process of natural selection.

We are selected, therefore we are

This problem of just-so storytelling is not some minor irritation to do with the perennial problem of giraffes, dismissable as some naïve caricature of what you really proposed in your theory of evolution. The problem runs much deeper and wider, embracing many new disciplines of evolutionary psychology, Darwinian medicine, liguistics, biological ethics and sociobiology. Here quite vulgar explanations are offered, based on the crudest applications of selection theory, of why we humans are the way we are. There seems no aspect of our psychological make-up that does not receive its supposed evolutionary explanation from the sorts of things our selfish genes forced us to do 200,000 to 500,000 years ago.

Did you know that women are genetically programmed to read maps badly? That step-children suffer more than usual at the hands of step-parents because of past genetic imperatives to look after one’s own genes only? That 'survival of the prettiest' is a seriously proposed evolutionary adapteive process, as if ugly people do not mate and reproduce? That we are mentally wired-up and doomed ruthlessly to compete – in particular, men. All of these and many more are accepted as naturally selected adaptations. And all currently diminish free will and choice.

Not only is there the embarrassing spectacle of psychologists, philosophers and linguists rushing down the road of selfish genetic determinism, but we are also shackeled with their self-imposed justification and giving 'scientific' respectability to complex behavioural phenomena in humans which we simply do not so far have the scientific tools and methodologies to investigate. There is a naivity about genetic determinism in both evolution and development that signifies intellectual laziness at best and shameless ignorance at worst when confronted with issues of massive complexity. . . .

As Peter Medawar said, there is an unfortunate sense in which your natural selection theory is too powerful for its own good. It has become the Swiss Army knife of biology: an all-purpose solution looking for problems. I hope to show you that for many scientists the 'problems' of biology are so ill-understood as so ill-defined that they are not at all sure what is is they are asking selection to 'solve'.

Dover's central conceit -- that he is writing letters to a dead but animate Charles Darwin and that Darwin is writing back -- quickly grows irksome and, after the first few letters, is honored mostly in the breach. Also, Dover is just wrong, and somewhat self-aggrandizing, in his argument that the mechanism by which mutations arise matters to Darwinism. For Darwin, mutation is and must be a black-box. Nevertheless, this is a good book on the effect of modern biological knowledge on Darwinism. The language and science are accessible and the book is well-written. Dover succeeds particularly well in his main goal: the metaphorical evisceration of Richard Dawkins.

Posted by David Cohen at May 10, 2004 8:47 PM