Besides his political failings, Thompson slowed his advancement by taking a near-heretical view of biological science. In the early twentieth century, biologists, reveling in—or reeling from—the triumph of Darwinism, tended to use evolution as a catch-all answer to biology’s “why?” questions. Why was any animal the way it was? Because natural selection favored it—never mind how. Biology was concerned with stories, not causes: Animals were seen as archives of evolution, and biologists’ main task was to use specimens’ anatomy to work out their history. Then, by comparison with other species, researchers could assign each creature its place on life’s family tree. As the British immunologist Peter Medawar later wrote, biologists “accepted the contemporary and far from adequate form of Darwinism in much the way that nicely brought up people accept their religion, that is, in a manner that contrives to be both tenacious and perfunctory.” Most zoologists were not much interested in how animals got to be the way they were, in either the long-term evolutionary sense or the short-term developmental sense. Nor were they interested in how animals worked; rather than ask why a bone took a particular form, they just wanted to compare it with the same bone in different species. But most of the striking advances in comparative anatomy were already decades old. Evolutionary biology was snoozing.

Perhaps this is why Thompson came to take a dim view of natural selection and genetics. He was interested in causes, thinking that when we see some feature in an organism, we should seek some underlying force that has brought the trait about. Simply to invoke heredity, as many biologists then did—for example, in the popular idea known as “ontogeny recapitulates phylogeny,” which hypothesized that the process of an animal’s embryological development re-enacted its evolutionary ancestry—seemed uselessly vague. “I should be [equally] at a loss to disprove the hypothesis that the Moon was made of green cheese,” Thompson wrote of the notion that evolution could explain how living things arrived at their present forms. He was no creationist: He granted that natural selection could weed out the unfit, but doubted its power as a creative force, able to explain why life took one form and not another. He also thought that physical similarities were a poor guide to shared ancestry—another position unlikely to endear him to



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