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Day February 12, 2007

Darwin Day 2007: Darwin’s Impact on the Social Sciences

In addition to being Lincoln’s birthday today, it’s also the 198th birthday of Charles Darwin, celebrated around the world as “Darwin Day.” In recognition of the day, I thought I’d share some thinking on Darwin’s contribution to the social sciences, because these are potentially as powerful as his direct effect on biology, if much less well developed. What follows is necessarily a sketch, since (a) much of it is reprising other sources, and (b) fully justifying and documenting this would turn it into an article or book, rather than a blog posting.

Ernst Mayr, the great biologist and architect of the Modern Synthesis, wrote in a 1959 essay that Darwin’s great contribution to biology was anti-essentialism, or what Mayr called “population thinking.” By this, Mayr meant that Darwin was one of the first biological thinkers to offer a theory of the evolution of species which did not rely upon changes to, differences in, or transformation of the “essence” of a species. In the older view, which goes back to Aristotle (at in terms of codifying this view; the origins of this view are much more ancient and are likely bound up in the cognitive science of “natural kinds”), each species is characterized by an “essence” or definition, which tells us what characteristics an animal, plant, and so on must have in order to belong to that species. The fact that each individual in a species is unique, and that often many individuals lack one or more essential characteristics, but are still considered part of the species, is explained away in Aristotelian essentialism as simply noise or reproductive error that causes the real world to be an imperfect reflection of the species’s underlying “reality.” Variation is thus explanatorily unimportant when species are viewed as characterized by pre-Darwinian biology. And the evolution of one species into another, over time, seems to run up against a massive gulf between two “essences.” One sees echoes of this “problem,” for example, in the objections of many contemporary anti-evolutionists when presented with what biologists believe is the abundant empirical evidence of evolution: the key words “intermediate forms” pop up as tell-tale signs, even though such a notion really arises only if one thinks a species has an “essence” between which a form could be “intermediate.”

Darwin’s great contribution, at least according to Mayr and others, was in founding modern evolutionary biology on a firm basis of anti-essentialism. In this case, what Mayr originally meant by “population thinking” (philosophers will recognize it as a variety of anti-essentialism) is that variation among individuals is not “noise,” nor is it meaningless error — variation among individuals is both the cause of evolution, and the great engine that powers the development of successive adaptations through the continuous (if occasionally roundabout) process of selection. Variation isn’t just important for selection, variation is critical for selection. No variation, no selection, as pointed out by the great mathematical biologist and statistician Ronald Fisher. In fact, selection might simply be the statistical consequence of having variation, some of which makes a difference of our life chances, in an environment where there aren’t enough resources, or enough room, or enough time, for every individual to succeed equally. Selection almost comes naturally when you think about the world through the lens of Darwin’s population thinking.

What has this got to do with social science and Darwin’s contribution to the human sciences? Potentially everything.