Friday, April 3, 2009

Blogging Mott Greene

Last night was historian Mott Greene's seminar in the public lecture series Introducing Darwin, which I've organized along with Maggie Osler, Tony Russell, and Jessica Theodor. Thanks to Shari and CJ for helping with the mikes and to CJ for taking some pictures.

Mott's talk was very good--first half some biographical remarks on "Darwin the man", then moving on to some very interesting remarks on "Darwin the myth", particularly the various ways in which Darwin has been enlisted by a wide range of people to support a wide range of ideas (he's been claimed as a justification for both unregulated capitalism and communism, for instance). As we've discussed, Darwin himself is notable for his insistence on getting his facts right and in his extreme reluctance to make inferences beyond what the facts will support. I'm sure this is why he was always very reticent about the implications (if any!) of his ideas for religion, economics, etc.

The point that will stick with me the most is Mott's remark that both religious conservatives and secular liberals today tend to resist Darwinian-style explanations for social phenomena. For instance, one can argue that the rise since the 1960s of feminism and gay liberation is not ultimately attributable to individuals making and responding to arguments about justice or equality. Rather, the ultimate drivers are economic pressures and reproductive imperatives. Appeals to justice and equality are at best the proximate mechanisms by which individuals happen to respond to those ultimate drivers of human behavior. The point is not that this explanation of the rise of feminism and gay rights is right or wrong, it's that people from across the liberal-conservative spectrum tend to dislike this kind of explanation, independent of any evidence.

One point Mott didn't make, which I got the chance to make briefly in response to a question from the audience afterwards, is that non-biologists who've developed "evolutionary" theories of economics or society (think of Hegel, Marx, Comte, and many others) tend to conflate Darwinian evolution with organismal development. That is, they tend to think of growth of an individual organism from child to adult as "evolutionary". It's not just famous thinkers like Comte who thought this way--the recent remarks from our own federal science minister indicate that he believes in "evolution" in the sense of individual development and change. To a biologist, this is a serious confusion. Darwinian evolution doesn't have a direction or goal or purpose (see Mayr's remarks in his introduction to the Origin). But the development of an individual organism does have a predetermined goal--to convert a fertilized egg into a functioning adult organism. If you claim that human societies are like developing organisms, that's a very different claim from the claim that human societies are like evolving populations.

This confusion between evolution and development has three obvious sources. One is that both involve "change over time", which is what "evolution" means in a colloquial sense. Second is that there are indeed directional trends in the history of life (e.g., increase in the average "complexity" of organisms since the origin of life), and it's natural (but incorrect) to think of such trends as analogous to the directional development of a newborn into an adult. Third is that it's very hard for non-specialists to grasp that the notion of "fitness" in Darwinian evolution is "relative fitness". All that matters in Darwinian evolution is your ability to survive and reproduce, relative to the other current members of the population. This notion of relative fitness does not imply that absolute fitness will increase over time (even in a constant environment), or that there is some "maximally fit" or "ideal" or "perfect" state toward which a population tends to evolve. I think this is the key Darwinian insight that even very smart non-biologists seem to find very difficult to fully absorb (though in fairness, evolutionary biologists don't help them by talking about evolution using engineering and hill-climbing metaphors that are fine in many respects but are subtly and importantly misleading in other respects). Evolution by natural selection is change over time that both lacks a goal or endpoint, but that is not simply random either (random evolution is genetic drift). Directional, non-random change--but the direction isn't "towards" anything. That's Darwinian evolution. As Mott noted, it's this kind of explanation that many people either misunderstand or find unpalatable.

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