Mendelian Exile

The years 1871 to 1930 were one long dry spell for sexual selection theory Wallace's criticisms were especially damaging, and gave female choice a bad name. Within a few years of Darwin's death in 1882, sexual selection had already come to be regarded by most biologists as a historical curiosity. Especially hard hit was Darwin's claim that sexual choice played a major role in human evolution. Edward Westermarck's History of Human Marriage of 1894 spent hundreds of pages trying to undermine the idea that premodern humans were free to choose their sexual partners. He thought that traditional arranged marriages destroyed any possibility of sexual selection. Like most anthropologists of his era, he saw women as pawns in male power games, and young lovers as dominated by matchmaking parents. He founded the tradition of seeing marriage primarily as a way of cementing alliances between families, a view that dominated anthropology until the last years of the 20th century

Not all biologists were hostile to sexual selection. August Weismann, a leading Darwinian at the University of Freiburg in Germany, included a positive chapter on sexual selection in his The Evolution Theory of 1904. After discounting Wallace's surplus-energy theory, and supporting and adding to Darwin's examples of sexual ornamentation, Weismann concluded that "sexual selection is a much more powerful factor in transformation than we should at first be inclined to believe." He added, "Darwin has shown convincingly that a surprising number of characters in animals, from worms upwards, have their roots in sexual selection, and has pointed out the probability that this process has also played an important part in the evolution of the human race." Nonetheless, Weismann's thoughtful assessment was swept away in the rising tide of genetics.

The rediscovery around 1900 of Mendel's work on genetics distracted biologists from Darwin's ideas. For young biologists at the turn of that century, genes were the way forward. Sexual selection was dead, and even natural selection was an unfashionable hobby of the older generation. Biology entered a reduc-tionistic phase of empiricism. Laboratory experiments on mutations attracted more attention and respect than grand theories of natural history. One of the leaders of the new genetics was Thomas Hunt Morgan, a Nobel prize-winner for his work on fruit fly mutations. In his 1903 book Evolution and Adaptation, Morgan dismissed sexual selection, concluding that "the theory meets with fatal objections at every turn." He proposed that sex hormones account for all sex differences in ornamentation, failing to realize that the sex hormones and their sex-specific effects themselves require an evolutionary explanation. Morgan's brave new world of mutated flies bred in bottles won over Darwin's world of ornamented butterflies breeding in the wild.

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