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.
- While logically and theoretically possible, when group selection does work it can be shown to be equivalent to gene-level selection, usually acting through interactions between individuals. It is thus more fruitfully modeled—and explained—by gene- and individual-centered explanations that often involve “inclusive fitness” (IF). IF is the idea that genes can gain a benefit not just by increasing the reproductive output (“fitness”) of individuals themselves, but via the interaction of those individuals with relatives or members of their group who carry the same genes. Human “altruism,” for example, is explained more parsimoniously by kin-selected IF models or other gene-centered approaches like reciprocal altruism (“I’ll scratch your back if you’ll scratch mine”)—or, in primates, by the notion that “altruistic” acts actually increase fitness by giving a good reputation to the altruist. Further, the data from nature show that the way altruism and cooperation operate in animals is more consistent with their evolution by gene- and individual-level selection than by group selection (see here for an explanation).
- Finally, I am not aware of a single adaptation in nature that can be explained better by group selection than by kin selection. (A single possible exception is the evolution of sexual reproduction, but we still know very little about how sex evolved.) In contrast, as the West et al. paper notes (see Table 1), as well as several responses to a 2010 Nature paper by Nowak et al. dissing kin selection, kin-selection theory and its underlying concept of inclusive fitness have been immensely fruitful in understanding the evolution of social behavior. It is kin selection and not group selection that has helped us understand things like sibling conflict, sex ratios in social insects and parasites, parent-offspring conflict, and genomic imprinting. Group selection has had no such success. A stark example of the impotence of the group-selection approach is given by West et al. (p. 378):
. . . [W. D.] Hamilton’s original model has been extended in numerous directions to match the biology of particular organisms, allowing more specific tests of theory (Frank, 1998; West et al., 2005). This allows us to quantify the relative use of the group selection and kin selection approaches, by examining the relative frequency with which these methods led to new areas of theory that could be empirically tested. We have performed this, and found that in 15 of 15 cases, it was kin selection theory that was used (Table 2; P = 0.00006, two-tailed sign test). Sex-ratio theory therefore provides clear statistical support for the usefulness of kin selection over group selection.
So if group selection is so intellectually and scientifically unproductive, why do we hear so much about it? I think there are two reasons.
First, its few proponents make a lot of noise. And those proponents include well-known scientists like Martin Nowak, E. O. Wilson, David Sloan Wilson, and Jon Haidt. Nowak, Tarnita, and Wilson published a big (and deeply faulty) paper in Nature asserting that group selection was a better explanation than kin selection for “eusociality”: the social system of animals, like bees and ants, that have sterile “castes” of workers that divide up colony labor, and have one or a few fertile queens tended by those workers. (For links, see my post on the scientific community’s rejection of that paper.) E. O. Wilson has incorporated many of these erroneous ideas into a new book, The Social Conquest of Earth, that will, because of his prominence, be widely read by the public. (I hasten to add that his other biological work has usually been superb.) Wilson’s book has not received much acclaim from scientists: it’s been severely criticized, for example, by Steven Mithen in The New York Review of Books and by Richard Dawkins in Prospect. I’ll be weighing in on the book later.
Jonathan Haidt, a well-known psychologist with a wide public following, has also pushed group selection in his new book The Righteous Mind. I’ve previously discussed his problematic TED talk on the book and his penchant for group-selection explanations of religion and human cooperation here.
The problem with all this is that the arguments for group selection are being made in books aimed at the general public, but the critical responses by evolutionary biologists are not only buried in technical papers, but involve arcane scientific arguments that sometimes use (horrors!) mathematics. So while group selection may flourish in the public mind, it’s moribund to most evolutionary biologists who have followed the technical debates in the literature.
Second, people want to believe in group selection. That doesn’t just include scientists like D. S. Wilson, who has made it his life’s mission to defend the concept, but, more importantly, the general public. We want to think that stuff like religion, cooperation, and altruism have spread by group selection because that involves the concept of harmonious and cooperating groups. Such a notion is deeply appealing to those who have a dislike for the idea of the “selfish gene,” mistakenly conflating that notion with the idea of selfish individuals. As all evolutionists know, or should know, cooperation and altruism can evolve via selfish genes!
Nevertheless, the idea of group-level adaptations has an innate appeal to those with a penchant for the religious and the spiritual. Why, just this morning the unctuous Krista Tippett (why do people listen to her?) interviewed D. S. Wilson on her “On Being” show on National Public Radio. The topic was Wilson’s attempts to improve his own city of Binghamton, New York using evolutionary principles of group selection. Last year, in a review of Wilson’s book The Neighborhood Project in The New York Times, I strongly criticized his evolutionary-based sociology.
So while group selection is moribund among evolutionary biologists and many evolutionary psychologists, the criticisms of the idea are buried in the technical literature while its vocal proponents write best-selling books. Behind much of this is the insidious Templeton Foundation, which has for some reason decided to promote group selection, probably because of its religious and spiritual connections and its link to “goddy” things like altruism and cooperation. Both D. S. Wilson and Martin Nowak, for example, are heavily funded by Templeton. And Jon Haidt not only was funded by two Templeton grants (here and here), but they also funded a sabbatical semester for him to write a book in 2003. Plus he won the Templeton Prize for Positive Psychology in 2001. (I guess there’s no prize for Negative Psychology.)
With all that money and all those megaphones behind it, the idea of group selection persists in the public mind while slowly dying in the scientific community. Yes, it’s dying, but it refuses to lie down.
West, S. A., A. S. Griffin, and A. Gardner. 2007. Social semantics: how useful has group selection been? J. Evol. Biol. 21: 374-385; doi: 10.1111/j.1420-9101.2007.01458.x.