Readers of this site will know that I’m not a big fan of group selection—the idea that adaptations in different species often result not from selection acting among individuals with different genetic constitutions, but from selection acting among groups, with some whole groups replacing others by virtue of their average genetic difference.
One supposedly group-selected trait is altruism, or any form of cooperation in which a “donor” of help receives little in return. In evolutionary terms, a genotype that sacrifices its fitness for a non-relative is at a disadvantage, and genes promoting such behaviors will be eliminated. But if different groups had different proportions of altruists, then perhaps the altruist-rich groups would survive at the expense of groups containing more selfish members, and the altruistic trait could spread via this differential survival of groups.
Besides the lack of empirical evidence for such selection in nature, there are two theoretical problems. First, group proliferation and extinction is much slower than the reproduction of individuals within groups, so it’s hard to see how the former could outweigh the conflicting pressures of the latter. Second, even if altruism is established via group selection, it’s vulnerable to the invasion of mutant individuals carrying non-altruistic genes: such “free riders” would be at an advantage within-all altruist groups. This would lead to the erosion of altruism, which would thus be unstable if it evolved through group selection.
Actually, pure altruism is exceedingly rare in nature, as we might expect if it’s subject to selection against individuals behaving that way. We do see it, though, in humans. Individuals regularly sacrifice their fitness (survival and reproduction) for unrelated individuals. Policeman and firemen, for example, do this, as do soldiers who risk their lives to save their comrades.
We don’t know whether such altruism in our own species has any genetic basis, but a new book review in Evolutionary Psychology by Michael Price of Brunel University, London, suggests that even if it does, one can account for it by selection on individuals rather than groups. Brunel is reviewing a new book by Samuel Bowles and Herbert Gintis, A Cooperative Species: Human Reciprocity and its Evolution (Princeton University Press, 2011), and it’s one of those rare reviews that makes its own contribution to science, bringing together a lot of evidence—in this case against the book’s thesis that human cooperation, which includes altruistic acts, evolved by group selection. (The pdf of the review, by the way, is available free at the links above and below.)
If you’re not interested in the technicalities, you can skip this paragraph from Price’s review, but I like it because it’s a mini-review of the evidence that human cooperation shows all the evolutionary signs of having evolved by individual rather than group selection. There are, of course, many evolutionary scenarios showing how cooperation and reciprocal altruism can evolve by individual selection alone, but Price summarizes the evidence that they did:
The view that group selection is needed to explain most human cooperation seems inconsistent with the fact that over the past several decades, most successful research on this cooperation has theorized that it is produced by individual-level adaptations (Price, 2011; Price and Johnson, 2011). The most influential and predictive theories of group cooperation have assumed that people contribute to group efforts in order to acquire resources for themselves, and that the main obstacle to successful cooperation is that members often do better individually by contributing less, or by consuming more, than would be optimal for group success (Hardin, 1968; Olson, 1965). These theories have served as the basis for an immense body of research which has demonstrated their predictive power; a quick overview of this research follows. Individual group members tend to acquire return benefits via their cooperation, by engaging in behaviors that can be regarded as n-person reciprocity or conditional cooperation (Fischbacher, Gaechter, and Fehr, 2001; Tooby, Cosmides, and Price, 2006), competitive altruism (Hardy and Van Vugt, 2006; Roberts, 1998), and status-for-altruism transactions (Price, 2003, 2006); they free ride frequently, when they can get away with it (Fehr and Gaechter, 2000); they monitor other members’ contribution levels so that they can detect and punish free riding (Ostrom, 1990; Price, 2006), and they experience more punitive sentiment towards free riders when they are more individually vulnerable to being free ridden (Price, 2005; Price, Cosmides, and Tooby, 2002); they engage in partner choice, which allows highly cooperative individuals to assort positively and thus avoid being exploited by free riders (Barclay and Willer, 2007; Page, Putterman and Unel, 2005); and they engage in more cooperation and third party punishment when they can acquire more reputational benefits from doing so, or when they detect cues that their actions are being monitored (Bateson, Nettle, and Roberts, 2006; Kurzban, DeScioli, and O’Brien, 2007; Milinski, Semmann, and Krambeck, 2002).
Price notes that the book’s main argument against individual selection is based on games conducted by experimental psychologists showing that cooperation continues even when the participants get no individual-level benefits. His response is that such games are not realistic models about how cooperation probably evolved in our ancestors:
The main problem with this suggestion has been pointed out repeatedly (Trivers, 2004; Burnham and Johnson, 2005; Hagen and Hammerstein, 2006; Price, 2008): Experimental economic games are not ecologically valid contexts from which to draw conclusions about how humans are adapted for one-shot, “anonymous” social activity. One-shot games are easy enough to orchestrate in experimental labs, but what would the analogue be in ancestral environments? Ancestrally, no experimenter was present to enforce the one-shot nature of an interaction, so social interactions were intrinsically iterative; for instance, if you cheated somebody, he might retaliate (Trivers, 2004). There’s no real reason, therefore, to expect the human mind to be adapted to a one-shot interaction context, or to process such experimental interactions as if they were truly one-shot. Further, for a behavior to be perceived as anonymous in the ancestral past, the actor would need to feel sure that no one else could consciously observe the act (e.g., she would need to be alone in the middle of the forest). This is nothing at all like the environment of an experimental lab, where you may be surrounded by other participants, you believe you are interacting with other conscious participants, and you know that your behavior is being recorded and scrutinized by researchers. Even if a participant consciously believes that his behavior is anonymous, his semi-autonomous adaptations producing his cooperative behavior may not act as if they believe this.
In sum, results from experimental economics games can be highly illuminating and useful for many purposes, but just like any kind of behavioral data, they have limitations. It is doubtful that experimental economic results actually reveal much of anything about how people are adapted for one-shot anonymous interactions, and they should not be regarded as evidence about the relevance of the individual as a vehicle of selection in ancestral environments.
Price gives the book a mixed review, praising it for its review of the literature on cooperation and of the models designed to explain it, but faults it for the unrealism of the formal models and its neglect of empirical data inimical to the book’s thesis. I haven’t yet read the book, but I found the review illuminating. So few book reviews these days do anything more than summarize the book’s contents and tack on a superficial positive judgment like, ‘This is a book that belongs on every graduate student’s shelf.”
Price, M. 2012. Group selection theories are more sophisticated, but are they more predictive? (A review of Samuel Bowles and Herbert Gintis, A Cooperative Species: Human Reciprocity and its Evolution. Princeton University Press: Princeton, NJ). Evolutionary Psychology 10:45-49