The Panda’s Thumb: More Reflections in Natural History
The Evolutionary Synthesis: Perspectives on the Unification of Biology
When I reviewed Stephen Jay Gould’s admirable Ever Since Darwin a few years ago, I expressed the hope that he would not lay his pen aside for too long. I need not have worried, for Gould is a natural writer: he has something to say and the inclination and skill with which to say it. His present collection is a series of essays that would give special pleasure to scientists, but they are sufficiently relaxed to be read with enjoyment by laymen too. A casual reader flipping through his pages may wonder what Mickey Mouse is doing in chapter nine (“A Biological Homage to Mickey Mouse”). Mickey is here to illustrate the characteristics thought by Konrad Lorenz to be responsible for the specially endearing characteristics of babyhood: “a relatively large head, predominance of the brain capsule, large and low-lying eyes, bulging cheek region, short and thick extremities, a springy elastic consistency, and clumsy movements.”
Without dissenting from Lorenz I wonder if this is the whole story. Few animals are more endearing than baby giraffes, which meet some but not all of Lorenz’s criteria; helplessness is surely another. I enjoyed this reminder of Mickey in his great days: it is a cultural tragedy that the brilliant early Disney was degraded and debauched by the witless and mindless imitators whose creatures have made television intolerable in the US on Saturday mornings.
Before I read Gould’s chapter fifteen I might have been tempted to dismiss as idiots people who enjoy such programs—but the correct technical term, I learn from Gould, is moron. Gould here adds his weight to those of us who insist that the pejorative and biologically most unsound term “Mongolism” be dropped in favor of “Down’s syndrome” as a designation of this unhappy congenital affliction. Down adopted the term because he regarded the syndrome as evidence of degeneration—of an atavistic return to a remotely ancestral human condition. Mongolian members of WHO objected to this and would have been still more annoyed if they had known that Down had entertained the possibility that the reversion was to a type even lower than that represented by modern Mongolians. Gould explains the whole matter admirably and in a way that everybody can understand. In defense of Down it should however be pointed out that Down worked and thought in the atmosphere of fearful wonderment about the implications for man of what was coming to be learned about heredity, development, and evolution that had been created by the writings of such as Francis Galton, Cesare Lombroso, Max Nordau, and of course Henrik Ibsen.
Gould’s favorite way of going about things is to pick upon some natural oddity and use it as a text for writing on some important biological problem. Thus the death within a few hours of birth of male mites of the genus Adactylidium is the text of the discussion of how the sex ratio comes to be fixed by natural selection. He adds, “Nature’s oddities are more than good stories. They are material for probing the limits of interesting theories about life’s history and meaning.” Thus Gould defends by implication (and quite rightly too) the dedicated bird watcher exultant in adding to his list of subjects the “rufous-crowned, peg-legged, speckle-backed, cross-billed and cross-eyed towhee.”
The chapter in Gould’s book that will arouse the most widespread interest (I first got wind of it in the European edition of the New York Herald Tribune) is that which has to do with an authentic nowhee: Piltdown Man. Between 1908 and 1912 an amateur archaeologist with some professional assistants came upon some rather puzzling bony remains in gravel in the village of Piltdown, Sussex, England. These were judged to be the remains of a very primitive man, Eoanthropus dawsoni (dawn man). In the gravel were also found some worked tools of flint and bone and some animal remains pointing to a find of great antiquity. Yet the fossil remains seemed inexplicably anomalous: for though the braincase looked very ancient and was unmistakably human, the lower jaw looked like that of an anthropoid ape.
No one knew what to make of it all and the anomaly was not clarified until the physical anthropologists J.S. Weiner and Kenneth Oakley with the moral support of Professor W.E. le Gros Clark divulged that the Piltdown skull was a fraud: some teeth had been artificially filed down, and aging of the human braincase had been simulated by the use of salts of chromium. Very many paleontologists had been skeptical all along and when the truth became known no living paleontologist of any distinction had reason to bemoan his gullibility. It was a disgraceful fraud and the question “Oodunnit?” still remains.
Suspicion has fallen on all the principals in the discovery, on the eponymous Charles Dawson and Sir Arthur Smith Woodward, author of The Earliest Englishman (London, 1948). Gould now makes a case against none other than Teilhard de Chardin, referring to A.S. Romer’s and Louis Leakey’s suspicion. That evidence is of course not direct: what it amounts to is that Teilhard could have been guilty. He was at a theological college in the neighborhood and was on Dawson’s team, and he had been on earlier expeditions during which he might have collected the fossil remains planted in the Piltdown gravel to give the finds an air of antiquity. There are also some anomalies of time and place in Teilhard’s letter to Kenneth Oakley congratulating him on his revelations.
Gould clearly had a good time following up his suspicions, and being a good writer he communicates his pleasure to his readers. But though Teilhard could have done it, I do not believe he did: I could as readily believe that he painted the supposedly paleolithic murals in the Lascaux caves (which like other cave paintings could probably do with a second look). The older Teilhard, the philosopher-scientist who wrote The Human Phenomenon, was in my very carefully considered opinion a silly old man, and the younger Teilhard can hardly be acquitted of gullibility, but I do not believe he was a criminal. The Piltdown forgery was a crime: “hoax” is too excusatory a word.
Gould writes sharply and amusingly about the considerations lying outside science that led to acquiescence in and even willingness to be deceived by the fraud. Clearly both racism and chauvinism played a part. The distinction—not yet quite the odium—of being the cradle of mankind is hotly competed for and Piltdown was in a way an Englishman’s answer to the disagreeable possibility that the earliest men may have been foreigners. In 1912 there would have been little dissent in England from the view that the English represented the highest evolutionary product of mankind, so what could be more natural than that the green and pleasant land should also have been the cradle of mankind?
What about the Panda’s Thumb? The essay that gives the book its title is a reflection prompted by Gould’s wonder at the skill with which the panda uses what is ostensibly its thumb to strip the leaves from bamboo shoots so that it can eat the stems. The puzzle is this: the hands and feet of vertebrates, though very variously modified, have characteristically five digits; the opposable thumb to which primates (such as ourselves and the manlike apes) owe so much of their dexterity is a modified finger, and there are four others. The panda, however, has five others. Does then the “thumb” represent a modified sixth finger? It is conceivable that it should because mutations affecting number and structure of the digits are by no means uncommon, but the panda’s thumb is not a digit at all. It is formed by the enlargement of a sesamoid bone at the end of the radius (a “sesamoid” is a supernumerary bone formed within a tendon or where a tendon rides over bone: the kneecap is one such). The panda’s hind foot has a counterpart in a tibial sesamoid that has not developed so far as the sesamoid in the hand.
The immediate purpose of Gould’s essay is to show how the opposable thumb could have developed making use of musculature already present and indeed already foreshadowed in the panda’s relatives the bears and raccoons. I think, though, that his more general purpose—especially laudable at a time when molecular biologists tend to elbow everyone else away from the limelight—was to show that comparative anatomy, in the tradition in which so many of us were brought up, is a most precise and exacting and certainly a very highly disciplined branch of biology, an opinion in which I heartily concur, knowing that in the hands of its really great practitioners comparative anatomy could almost be regarded as an art form. This does not mean that I depreciate molecular biology: it is not a matter of competition—there is room and need for both.
I very much hope that sociologists are among Gould’s readers and that they turn first to chapter eight, from which they may learn something to their advantage. Modern biologists are peevishly aware that amateur sociobiology is rapidly reaching the dimensions of a public nuisance. Evolutionary changes are thought to come about because it is desirable that they should do so, and behavioral traits are received into the genome, the organism’s set of chromosomes, “for the good of the species.” This is not a Darwinian notion. Edward O. Wilson was fully aware of the pitfalls in reasoning of this kind and that is why he settled upon “altruism” as the central theoretical problem in sociobiology. If the evolution of altruism can be explained, even in as extreme a form as “laying down one’s life for one’s friend” or committing a public-spirited suicide, as lemmings are alleged to do (I do wish Gould would look into this illusion—for such I believe it to be), then the occurrence of evolutionary changes “for the good of the species” would be very much easier to understand.
“Kin selection”—a notion of W.D. Hamilton’s—is widely agreed to be the key to the answer. The notion is made self-evident by a characteristic remark of J.B.S. Haldane’s, quoted by John Maynard-Smith, to the effect that he was prepared to lay down his life for two brothers or eight cousins. If there existed a genetic combination that conferred this degree of altruism upon Haldane it should increase his representation in the population because of the sharing of genes between blood relatives.
In the course of his discussion Gould quotes the aphorism that embodies one of the genuinely fundamental truths of biology: “that a chicken is just the egg’s way of making another egg.” I very much wish I knew who first said this. Gould attributes it to Samuel Butler, but Butler himself mentions it in his Notebooks (London, 1911) as a saying already familiar and in common use.