The demise of group selection
By JERRY COYNE - WHY EVOLUTION IS TRUE
Added: Sun, 24 Jun 2012 22:13:22 UTC
In the nicest possible way and with great respect, could I make two suggestions to would-be commenters, based on past experience when this topic has come up-
Please pause before offering your own common sense view. There are topics in science, of which this is one, where common sense is not a good guide. If it were, professional biologists would not have been arguing about it for five decades. There is a large back literature in which the likelihood is strong that whatever commonsense view you put forward has already been proposed and exhaustively discussed. As an analogy, common sense is notoriously misleading when we try to understand quantum mechanics. If you could do physics by common sense, we wouldn't need physicists. To a lesser extent, something like the same thing applies here.
Please note that Homo sapiens is a very peculiar species and probably not the best testbed for the theories under discussion. That is not to say that the theories under discussion will forever be irrelevant to human affairs. But the argument at hand is sufficiently difficult that it is worth trying to understand it and solve it, at least to begin with, without the additional complications that arise with human culture. It's not a bad idea to think about lions or ants or acorn woodpeckers as your model animal when trying to get to grips with these evolutionary theories.
The idea that adaptations in organisms result from “group selection” (selection among groups that differentially bud off subgroups, with those having good “group traits” becoming more numerous), rather than from selection among genes themselves, usually within individuals, has undergone a bit of resurgence in popular culture. This is in stark contrast to the views of most evolutionary biologists, who see group selection as a logical possibility, but one that doesn’t easily work in theoretical models and, more important, has explained almost nothing about nature. In contrast, the gene-centered view of evolution worked out by biologists like W. D. Hamilton, Robert Trivers, and John Maynard Smith, and popularized by Richard Dawkins, has been immensely fruitful.
I’ve posted a lot on the intellectual vacuity of group selection, particularly its failure to explain the evolution of traits like human altruism and cooperation (see, for example, here, here, and here). If you want an elegant and easily digestible explanation of the weaknesses of group selection, Steve Pinker has just published a nice essay on John Brockman’s Edge website, “The false allure of group selection.“ If you’re interested in seeing three smart biologists take group selection apart, there’s an excellent paper by West, Griffin, and Gardner (reference below), which you can download for free here (the paper is not too hard, and the meat extends from pp. 376, beginning at “Error 3: the new”, to p. 379, bottom of Table 2).
There are several reasons why group selection has waned in popularity among evolutionists:
- Group selection is a fuzzy and nebulous concept that is far less coherent than is gene-level selection (see Pinker’s essay for an explanation)
- As I said above, when group selection does work in theory, it can be shown to be mathematically equivalent to gene-level selection involving “inclusive fitness.” But the group-selection scenarios are far more unwieldy, and are often so complex that they can’t be modeled. As West et al. note:
- “No group selection model has ever been constructed where the same result cannot be found with kin selection theory”.
- “The group selection approach has proved to be less useful than the kin selection approach.”
- “The application of group selection theory has led to much confusion and time wasting.” It is, as the authors say, “easy to misapply, leading to incorrect statements about how natural selection operates,” it is “not distinct from kin selection”, and it “often leads to the confusing redefinition of terms and the use of confusing jargon.”
- There are formidable theoretical problems with many concepts of group selection. These include the fact that individuals reproduce faster than groups, so that an adaptation that is good for groups (say, pure altruism, in which individuals sacrifice their reproduction through behaviors that bring no benefits to the genes producing such behaviors), won’t spread because the rate of propagation of groups is undermined by the evolutionary disadvantage of altruistic behaviors within groups (non-altruists, or “cheaters,” will replace the altruists since they get the benefits without the costs). In other words, altruistic groups may do better than non-altruistic ones, but that won’t produce species-wide altruism because non-altruists do better than altruists within groups—unless, of course, altruists aren’t “pure” altruists and their genes reap some benefit from the behavior, in which case it’s kin selection.
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