Small Items with Big Implications

John Hedley Brooke

  • Hen’s Teeth and Horse’s Toes: Further Reflections in Natural History by Stephen Jay Gould
    Norton, 413 pp, £11.95, September 1983, ISBN 0 393 01716 8
  • The Great Chain of History: William Buckland and the English School of Geology, 1814-1849 by Nicolaas Rupke
    Oxford, 322 pp, £22.50, September 1983, ISBN 0 19 822907 0

In the concluding essay of an adventurous collection, Stephen Jay Gould observes that most ‘classic stories’ in science are wrong. There are good reasons why he is right. In their reconstruction of the past, practising scientists have been apt to celebrate the insight of those who anticipated their own ideas, tacitly dismissing those who were blind to where the future would lie. The result has often been sterile histories, distorted by a preoccupation with confirming the present. The apocalyptic aspects of science, with the next breakthrough just around the corner, may add to the distortion by a more general undervaluation of the past. And the distortion is often sealed by an appeal to history for corroboration of fashionable stereotypes of scientific method, the classic discoveries having been made by ‘prepared minds’ whose interrogation of nature was conducted according to the canons of inductivism, hypothetico-deductivism or some transcendent hybrid. Consequently, science carries along a false history which, like a recessive gene, can pass undetected from one generation to the next. Not one of the least justifications for serious scholarship in the history of science is that it can rectify the distorted vision which the textbook traditions enshrine. It is a justification which Gould happily accepts. Whilst the majority of the 30 essays which compose Hen’s Teeth and Horse’s Toes divulge the latest news in natural history, at least a third have the additional merit of bringing a critical history of science to a larger audience. Gould’s iconoclastic remark occurs in a discussion of a 19th-century ‘fact’, the history of which raises interesting questions indeed. This ‘fact’ was the ability of sires to influence subsequent progeny not fathered by them. One example was familiar and acceptable to Charles Darwin: the successive offspring of Lord Morton’s mare. Crossed with a quagga (a now extinct zebra with stripes confined to neck and forequarters), the Arab mare delivered a hybrid with stripes in evidence. Subsequently mated with a black Arab stallion, the mare again produced an offspring resembling the quagga. This curious form of action at a distance was given a name (telegony) and even inspired a major programme of experimental breeding. As a ‘fact’ it was comfortably embedded in most of the genetic theories of the time (including Darwin’s own) and was only rejected when August Weismann made it impossible in theory – the theory he erected on the continuity of the germ plasm and its protection from extraneous influence. Now for the moral. By contrast with the adage that an unquestioned theory may be overthrown by one novel fact, we have the illuminating case of an unquestioned fact being overthrown by one novel theory.

This example epitomises Gould’s predilection for the curious, for seeming trivia in both natural history and its history from which engaging lessons may be drawn. The essays here, with only three exceptions, have already appeared in the author’s monthly column for Natural History Magazine. The one theme which unites them is that they contain ‘small items with big implications’. If Darwin’s path to the validity of evolution was strewn with barnacles and worms, so Gould, in turn, would have us consider the minutiae of the biological world: species of anglerfish in which the male, minute compared with the female, fuses so permanently with her that he becomes dependent upon her for nutrition; ichneumons with their habit of laying eggs in caterpillars and the ensuing grizzly death that so offended Darwin’s sensibilities; true mites, histiostoma murchiei, in which the female is spared the task of finding a husband by laying them – the husband-producing eggs, that is; the spotted hyena in which the female sexual apparatus so closely mimics that of the male that the clitoris is no smaller than the penis; toothless hens whose chick epithelium can still produce enamel and induce dentin in mice; horses with more toes than the statutory hoof. Each of these curiosities, and the many more with which the book abounds, provides the occasion for a homily on what may or may not be inferred about nature and science. His anglerfish shows there is no law in nature which says that females must be smaller and subordinate to males. The ichneumon shows that aesthetic and moral values cannot, in any case, be deduced from the products of natural selection. The mode of sex determination devised by ancient and lonely mites, and its subsequent role in the very different and highly differentiated societies of ants and bees, demonstrate that the current utility of a particular feature may be a poor guide to its evolutionary origin. The genitalia of the female spotted hyena invite explanation in terms of developmental anatomy and not merely adaptive utility. The properties of chick epithelium illustrate the existence of a latent genetic flexibility retained from a distant past; while extra digits in horses suggest that genetic systems may contain hidden capacities for producing large effects from small changes.

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