Thanks to Peter Turchin and Michael Hochberg for creating and managing the Social Evolution Forum, which has become an excellent arena for high-level discussion. Thanks also to my colleagues who took the time to write commentaries and to readers who responded with their comments. In addition to this general reply, I have also provided comments in the ‘response’ section of each commentary.
Equivalence check: Superficially, it appears that two commentators (Pagel and Sanderson) agree with my assessment about cooperation but not about group selection, while the others (Hewson, Zimmerman, Hochberg and Whitehouse, Bulbulia, Greenhill, and Gray) are more accepting of group selection. In fact, Pagel and Sanderson are just as accepting of group selection when terminological issues are resolved. In a previous essay published in the Social Evolution Forum, (Wilson 2012), I focused on the concept of equivalence, whereby scientific frameworks are different but worthy of coexistence. Equivalence requires an ability to understand and translate between frameworks, similar to translating between languages. Scientists who insist on employing only one framework run the risk of committing errors comparable to “I don’t speak Russian; therefore everything stated in Russian is wrong.”
This kind of error is on display in the comments by Pagel and Sanderson. The ‘language’ of multilevel selection is easy to speak. It involves identifying where fitness differences exist in a multi-tier hierarchy of units. I clearly indicate my use of the multilevel framework in my target essay, as in this passage concerning the evolution of any given genetic trait: “…did it evolve by virtue of increasing the fitness of genes relative to other genes within the same organism, individuals relative to other individuals within groups, or groups relative to other groups in the total population?”
Pagel and Sanderson are either unable or unwilling to speak this language. Consider this passage by Pagel: “In the simplest case, imagine that you inhabit a group of two and that by helping each other you can achieve more than twice as much as the two of you working alone. Now ramp this scenario up to a larger group. …The returns from cooperation means that what looks like altruism, is really a form of enlightened self-interest.”
Pagel is not speaking the language of multilevel selection theory. If he did, he would see that there are no fitness differences among cooperators within single groups in his example. The fitness differences exist at the group level—groups of cooperators contribute more to the total gene pool than groups of non-cooperators or solitary individuals. If cooperation is cost-free, then the trait is neutral with respect to within-group selection and evolves by between-group selection given any variation among groups. If cooperation involves any private cost, then cooperators are less fit than non-cooperators within groups, which between-group selection must overcome for cooperation to evolve in the total population.
Or consider this statement by Sanderson: “Of course there are cultural traits that may benefit the group as a whole. But all this can mean is that these traits benefit all of the individual members of a group”. Sanderson is not speaking the language of multilevel selection. If he did, he would see that there are no fitness differences among individuals within groups. Natural selection requires fitness differences, and fitness differences at the group level are required for the cooperative trait to evolve in the total population in his own example.
I do not insist that my colleagues speak the language of multilevel selection in their own work. I appreciate that terms such as “self-interest” and “altruism” can be defined in numerous ways; e.g., in terms of absolute fitness rather than relative fitness within groups. But before I brand their results as wrong, I do an equivalence check by translating their examples into my preferred framework. This is what Pagel and Sanderson fail to do in their commentaries.
I invite readers to do an equivalence check for all of the examples in all of the comments on my target essay. By my reckoning, not only do Pagel and Sanderson agree with me on the importance of cooperation, but they also agree with me and the other authors on the importance of between-group selection, as defined within the framework of multilevel selection theory. As Peter Turchin comments on Pagel’s use of the phrase “groups as collective survival vehicles” in his book Wired for Culture, “That’s group selection!”
On groupishness: Group selection does not favor altruism or cooperation per se. It favors any proximate mechanism that causes groups to differentially contribute to the gene (or meme) pool of the total population. Some of the mechanisms appear altruistic in the conventional sense of the word and require substantial individual cost to benefit the group. Other mechanisms might appear selfish in the conventional sense of the word, and need not require much or even any self-sacrifice. Some forms of competition among individuals within groups also benefit the group and will be favored, rather than suppressed by group-level selection. Complex social interactions often result in multiple stable equilibria, which are internally stable by definition. Selection among equilibria results in well-adapted groups that are also internally stable, unlike the internal instability characteristic of altruism. I have emphasized these points in other publications but not sufficiently in my target essay, especially when I stated “it all revolves around cooperation.” I therefore agree with Peter Turchin in his response to Pagel that ‘groupishness,’ not ‘cooperation,’ is the best general term for describing the products of group selection.
These points are part of the consensus exhibited at the Ernst Strungmann forum and are appreciated by some of the commentators but not others. The only evidence that Pagel and Sanderson will accept for group selection is the kind of self-sacrificial altruism found in social insect colonies. All other mechanisms that benefit groups are interpreted as “enlightened self-interest” and are assumed to be explicable without invoking group selection. The only way to evaluate this claim is to perform an equivalence check on a trait-by-trait basis. Please see my response to their individual comments for more.
On the rewards and punishments that support groupish behavior: Human social groups bristle with mechanisms that punish bad behavior and reward good behavior. When these mechanisms are in place, behaving prosocially becomes individually advantageous and behaving antisocially becomes just plain stupid. Nevertheless, we still need to explain how the rewarding and punishing mechanisms evolve. Causing others to promote the common good is usually itself a common good that requires time, energy, and risk on the part of the rewarding and/or punishing individual, which economists term a second-order public good.
These points are part of the consensus exhibited at the Ernst Strungmann forum and are appreciated by some of the commentators but not others. Consider the example of reputation discussed by Pagel. Good deeds increase one’s reputation and bad deeds decrease one’s reputation, so individuals who care only about their reputation will perform good deeds. But what are the traits required for others to bestow a high or low reputation upon a given person? Do these traits evolve based on relative fitness advantages within groups, or do they require between-group selection?
On distinguishing between psychological and behavioral definitions of altruism: The distinction between proximate and ultimate causation in evolutionary theory requires separate definitions of altruism based on psychological motives (proximate) and phenotypic consequences (ultimate). If we imagine a 2×2 table with psychological altruism and selfishness as rows and behavioral altruism and selfishness as columns, all four combinations are possible. This should be common knowledge among all evolutionists, so it is discouraging that some of the commentators appear to conflate psychological and behavioral definitions. Consider the following passage by Sanderson: “The point about conquest is especially important because it is about one group defeating another. On the surface that looks like group selection. But is it? I would say no. It isn’t a matter of a whole society against another, but of the most powerful members of a society conquering others to gain the spoils. Do they want to share the spoils with the rest of society? Not really.” Sanderson is comparing apples and oranges when he uses psychological motives to argue against the fitness differences of traits within and among groups. This example is problematic in other respects that I address in my response to Sanderson’s commentary.
On consensus: Sanderson questions the significance of the consensus exhibited at the Ernst Strungmann forum, even given that it took place. I agree with Sanderson that it is silly for anyone to claim that a given position is true because X people endorse it, no matter what the value of X. Nevertheless, science is not a frictionless pendulum of ideas. Results are established that are durable enough to be called facts, and these tend to become widely accepted. The earth is round and very old. Continents drift. To these we can add the fact that many traits evolve on the basis of the differential fitness of groups, despite being selectively disadvantageous within groups, as these terms are defined in multilevel selection theory. What’s new is that large numbers of scientists are accepting this fact at face value and do not regard equivalent descriptions as a denial of the fact.
On using consensus and equivalence to guide empirical research: The commentaries by Hochberg and Whitehouse and Bulbulia, Greenhill, and Gray are especially welcome because they show how the consensus exhibited at the Ernst Strungmann forum can be used to guide empirical research. I wholeheartedly agree about the importance of history as a fossil record of cultural evolution, which is often so rich that it puts the biological fossil record to shame. Narrative histories often provide sufficient detail to evaluate how new cultural forms originate and spread in competition with alternative forms. An important book in this regard is Robert Bellah’s (2011) Religion in Human Evolution: From the Paleolithic to the Axial Age (an audio interview that I recently conducted with Bellah is available here) Quantification, including the phylogenetic methods described by Bulbulia, Greenhill, and Gray, adds additional power. Please see my response to their individual commentaries for more. The most important general point is that the entire theoretical and empirical toolkit that is used to study biological diversity can be used to study cultural diversity. We can look forward to the same kind of integration for the study of culture during the 21st century that took place for the biological sciences during the 20th century (and continuing).
Bella, R. (2011). Religion in Human Evolution: From the Paleolithic to the Axial Age. Cambridge, MA. Harvard University Press.
Wilson, D. S. (2012). Clash of Paradigms: Why proponents of multilevel selection theory and inclusive fitness theory sometimes (but not always) misunderstand each other. Social Evolution Forum, July 13.