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.

The social sciences have long been characterized by modes of explanation which draw upon Aristotelian essentialism for their conceptual structure, just as pre-Darwinian biology did. A simple example from my own field of anthropology illustrates the problem nicely: for many years, anthropologists classified whole societies as belonging to one of several “levels” of organization and thus social evolution. Societies could be “bands,” “tribes,” “chiefdoms,” or “states.” Furthermore, societies were often seen as moving through this progression, from simpler to more complex forms of organization. While this scheme is not often used in its raw form today, and the notion of a straight-line, unilinear “progression” from one form to other in rigid fashion has been thoroughly debunked within the social sciences, it’s not completely gone. One still reads professionals characterizing a particular social group being at the “chiefdom level of organization,” as if there were a natural “reality” to these categories that all societies had to fit. Even if the people in question aren’t really meaning to allude to unilinear forms of social theory, the association is there and the concepts hard to get away from.

This is nowhere more evident than in popular and political discourse, where one sees echoes of straight-line, unilinear cultural change in assertions that all societies trend towards democracy, or towards capitalism, or towards market economies, or really towards any singular and unitary goal. I don’t need to point any further than Francis Fukuyama or Robert Wright, both of whom defend fairly unlinear, 19th century views on the “necessary” path of cultural and historical change. Their views are far from isolated, far from unpopular, and far from lacking influence.

Darwin’s gift to the social sciences is really the same as it was to biology: the tools to reject such remnants of the “Great Chain of Being” and Aristotelian essentialism by replacing it with accounts of social and cultural change that recognize the importance of variation, of individual action, and of selective and other population-level processes that shape how that variation is lost or retained over time. Darwin’s gift is potentially a richer, more predictive, but also less “artificial” account of where we came from and what our possibilities are going forward. I say this because it treats our diversity of action, thought, and ideas as the critical ingredients for who we are and how we’re changing, rather than simply noise or randomness to explain away once we think we see a clean, neat, global historical pattern into which we believe everyone fits.

Darwin’s gift isn’t a particularly easy one to use, however. Leaving aside the 19th century legacy of progressive, essentialist cultural evolution for a moment, much of the social sciences in the 20th century were under the sway of rational choice theory in various forms. Rational choice theory, and neo-classical economics, are each based on very essentialist ways of looking at behavior. Preferences are assumed to be static, rather than evolving as a consequence of population-level processes as a whole, and given static preferences and decision-theoretic rules which are assumed to be constant within the population (i.e., part of “human nature”), rational choice theory in its various guises predicts the “equilibria” that will arise. These equilibria are the mathematical echoes of the “essences” one sees in pre-Darwinian accounts of species. Departures from equilibria are unimportant in these theories, because our assumption is that rational calculation and exogenous preferences would quickly lead back to equilibrium. Economic and political science “equilibrium theories” thus treat variation as noise — not as something important as part of our explanations.

The assault on such thinking has been slow in coming, but it is happening across the social sciences. It’s occurring in the form of non-equilibrium, individual-based models in economics, in evolutionary game theory which replaces “common knowledge” and rational agents with variation and replicator dynamics, and with strong interest in the dynamics of change rather than simply the endpoints or “equilibria.” I take these trends as good signs that we’re learning to use Darwin’s gift. Development of new models and theories, not to mention tests and experiments, to replace rational choice, essentialist social classifications and Homo economicus don’t happen overnight. But the effort has been going on sporadically for 30 years or so, and it’s gaining steam.

Interestingly enough, the strong interest in critical, Continental, or “post-modern” philosophy within the social sciences is also a reflection of Darwin’s gift. Despite disagreements about the nature, place, and methods of science and inquiry (and in particular, the useless fights over “scientism” and “relativism), both evolutionary social scientists and post-modernists are simply trying in different ways to figure out the consequences of anti-essentialism for describing and understanding the human experience. We have much to talk about, but we currently still speak very different languages and there are few, if any, good translators (the Richard Rorty of Consequences of Pragmatism being a notable exception, in my view). Bridging the gulf here, in pragmatic rather than contentious or zero-sum ways, is important to a unified and diverse social sciences, but it is an effort that’s hardly begun, let alone one that is gaining any ground.

Clearly there’s a lot one can say and argue about this topic. Before this day ends (and it’s getting quite late), I wanted to simply recognize the core contribution that Darwin’s “population thinking” and anti-essentialism has begun to make in the social sciences, and look forward to a day when we have more results from its deployment to show, particularly to those who remain skeptical of its “difference” from traditional modes of inquiry in the human sciences. And in recognizing this, to celebrate in a small way the life and anniversary of one of our greatest scientists and thinkers. He changed us and our ways of thinking more than he knew, and even more than we probably still recognize.