Wednesday, April 20, 2011

Kin Selection vs. Group Selection

Where does altruism come from? Why do animals regularly risk or even sacrifice themselves for the good of others?

It is a hard problem for evolutionary theory, as Darwin recognized. The most popular explanation for the past 40 years has been "kin selection," proposed in 1965 by William Hamilton. Kin selections posits that when animals sacrifice themselves for their siblings and cousins, who share many of their genes, they are helping to pass enough of their genes to the next generation to make the sacrifice evolutionarily worthwhile. Among the scientists who helped make kin selection into textbook orthodoxy, the most prominent was E.O. Wilson. There has been much stir in the world of biology lately because E.O. Wilson himself has come out strongly against kin selection:
Over the course of subsequent decades, Wilson came across evidence that made him doubt the connection between genetic relatedness and altruism. Researchers were finding species of insects that shared a lot of genetic material with each other but didn’t behave altruistically, and other species that shared little and did. “Nothing we were finding connected with kin selection,” Wilson said. “I knew that something was going wrong — there was a smell to it.”
Now, mathematics can show, and has shown, that kin selection could work, but it does not show that it is the actual mechanism driving altruism. There has always been an alternative theory out there, a theory that is much older than kin selection: group selection. Now Wilson has become the most prominent advocate for the group selection model:
The alternative theory holds that the origins of altruism and teamwork have nothing to do with kinship or the degree of relatedness between individuals. The key, Wilson said, is the group: Under certain circumstances, groups of cooperators can out-compete groups of non-cooperators, thereby ensuring that their genes — including the ones that predispose them to cooperation — are handed down to future generations. This so-called group selection, Wilson insists, is what forms the evolutionary basis for a variety of advanced social behaviors linked to altruism, teamwork, and tribalism — a position that other scientists have taken over the years, but which historically has been considered, in Wilson’s own word, “heresy.”
It will be very hard to resolve this argument, because both models predict altruistic behavior, and lo, we have altruistic behavior. The argument is based on a very technical and subtle argument about the relationship between equations and the world. In other words, this is an argument not so much about science as the philosophy of science -- and you all know how good philosophers are at settling arguments. It may turn out that both models apply, in different situations.

I bring this up mainly to make the point that science is not, as certain pseudo-intellectuals -- Ayn Randians, Marxists, barroom rationalists, middle school shop teachers -- like to say, "obvious." Science is hard. To understand science at a high level it really is necessary to think philosophically: to frame problems correctly, to ponder what we mean by cause and effect in various situations, to consider the relationship between equations and models. Scientists are all metaphysicists, whether they want to admit it or not.

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