The modern synthesis and the blank slate

March 1941-March 1946

For most of the later nineteenth century after the publication of On the Origin of Species. biologists were skeptical of Darwin’s proposed mechanism of evolutionary change – natural selection. It was only in the twentieth century that this began to change. When Mendel’s work on heredity was rediscovered in 1900, it was originally seen by many as antithetical to Darwinism. But with the pioneering theoretical work of Fisher, Haldane, and Wright, and the subsequent empirical work of Mayr, Dobzhansky, Simpson, Huxley, Stebbins, and others, Darwin’s theory of natural selection and Mendel’s theory of heredity were combined in what came to be called “the modern synthesis.” Julian Huxley’s book Evolution: The Modern Synthesis marked the coming of age of the theory.

In an earlier post I noted how Lyell and Darwin’s embrace of gradualism in explaining the past (as well as George Eliot’s celebration of Dorothea Brooke’s “unhistoric acts” and “hidden life”) had something to do with the political climate in England in the years after the French Revolution and Napoleon. Evolution: The Modern Synthesis was first published in 1942. It’s no surprise that the modern synthesis too was a product of its time, when Nazi Germany and the Soviet Union offered gruesome antithetical demonstrations of how not to think about evolution, genes, and behavior.

Not coincidentally, at the same time that biologists in England and the United States were advancing the modern synthesis, social scientists – cultural anthropologists, behaviorist psychologists – were coming to embrace a strong blank slate view of human nature. (Carl Degler tells the American side of the story in In Search of Human Nature: The Decline and Revival of Darwinism in American Social Thought.) There grew up something amounting to a peace treaty between evolutionary biology and the social sciences, with the two fields agreeing to respect each others’ spheres of influence. Social scientists would leave biology to the biologists, accepting, for example, that neither a good upbringing nor acquired skills can improve your genes. Biologists in turn would largely steer clear of addressing social behavior. For example, the theory of sexual selection, which Darwin developed, and Fisher elaborated, was mostly dropped from the modern synthesis as it matured. Huxley argued (pretty unconvincingly in retrospect) that the elaborate mating dances and ornaments found in so many species were not a product of sexual selection, but merely helped to let individuals choose the right species of mate. Westermarck’s pioneering work on the evolutionary psychology of incest avoidance and the incest taboo was largely shelved in favor of the shakier theories of Freud and Lévi-Strauss. Even Darwin’s work on emotional expression, which might have seemed fairly anodyne politically, was largely rejected by anthropologists. And the study of prehistory was affected as well.

It was only beginning in the 1960s and 1970s, with the rise of sociobiology, that evolutionary biologists returned to seriously addressing social behavior. Sociobiology: The New Synthesis (1975), by E. O Wilson, made a nod to Huxley in its subtitle. It also announced the end of an intellectual peace treaty, and the opening of an intellectual war that persists up to the present.

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One thought on “The modern synthesis and the blank slate

  1. Pingback: Globalization and its discontents | Logarithmic History

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