7 June
Dear David Sloan Wilson,
Thanks for your latest letter, though I’m increasingly confused on what you mean by “selection,” “group,” and other terms in evolutionary biology that need to be clarified if we are to apply them to cultural evolution.But let us proceed in order. You keep bringing up Peter Turchin’s work, so let’s talk about it. When I checked Peter’s website, it lists exactly one paper, published in 2011 in Structure and Dynamics, that explicitly mentions multi-level selection theory. It’s an interesting paper in many respects, but it also represents a good example of the failure (or, better, the irrelevance) of the approach.First off, Peter spends a lot of time writing about historical facts, trends, and potential causes of change. Just like any good old fashioned historian would. He introduces MLS in three equations: the original Price equation, a modified version that sets the conditions for the spread of prosocial behavior, and a third one describing the conditions for the spread of cultural practices promoting group unity.That’s great. Except that nowhere in the paper are these equations then used in combination with actual empirical data! The Price equation is structured around these variables: the difference in cooperators from one generation to the next; the between- and within-group genetic variances; the between-group selection coefficients; and the within-group selection coefficients. But Peter never estimates any of these quantities. Because he can’t. We are not going to know how many people or sub-groups could reasonably be classified as cooperators or non-cooperators in any given instance, like the Peloponnesian War. More importantly, again, it is fuzzy to the level of incomprehension what counts as a group and what sort of selective pressures any such group was under.Both you and him appear to think that these are just details, no more complicated than accounting for horizontal gene transfer in biological systems. But, once more, the proof is in the pudding, and I haven’t seen any yet.The rest of Peter’s paper is interesting, and a good example of quantitative analysis applied to historical questions. We learn that “mega-empires” arise when there are domesticated animals that are good for warfare: horses more than camels, camels better than nothing. I’m not sure any historian would be shocked to discover this, though. Figure 3 graphs time vs the territory occupied by empires. There are two spikes, corresponding to the invention of chariot warfare and to the introduction of mounted warfare. Good to have the data, but do we really want to kid ourselves in thinking that this is a novel insight generated by evolutionary theory?The most interesting bit comes on p. 17, where Peter, again correctly, says that “many different mechanisms” are involved in social evolution. One such mechanism, he admits, is that “human societies, or their decision-making institutions, may anticipate the eventual results of group selection in many contexts and get there first. Such anticipative selection, when it works, will yield the most rapid rate of social change.” He may call this “anticipative selection,” but I call it conscious volitional decision making, something that is nowhere to be found in Price’s equation and that constitutes the crux of the problem and the foundation of my skepticism: we can think about stuff before acting on it, and our thinking is influenced by many factors, including cultural institutions (states, ideologies), personal motivations (friendships, love), and so forth. Do we seriously contend that all of that can be satisfactorily captured by exactly four variables?Peter states, correctly, that “cultural group selection operates on the ability of groups to avoid dissolution and to reproduce themselves.” I ask again: what counts as a group, and why? Was Athens a group? Was the Peloponnesian League? Where the Spartan helots? The Athenian aristocrats of whom Alcibiades was a member? The regular citizens who voted to kill Socrates? And more: did these groups reproduce? How? What was the offspring? Without clear answers to these questions, that can be quantitatively operationalized in mathematical structures such as the Price equation, we’ve got nothing but a potentially misleading metaphor.Peter adds (emphasis mine): “The model advanced in this paper avoids specific assumptions about the nature of cultural variation and the mode of cultural evolution. I acknowledge this as a serious theoretical problem, but I believe that we do not have to wait until the mechanisms of cultural evolution are worked out in detail. The example of Darwin’s theory of evolution, which was an extremely useful vehicle for organizing research even before the nature of genes was understood, is heartening.” No, it isn’t. Peter seems to forget that Darwinism went into an eclipse and was considered near-dead by paleontologists, developmental biologists and others at the turn of the 20th century. What revived it was precisely the elucidation of the mechanisms of inheritance. That’s what the Modern Synthesis was all about. We haven’t had anything remotely like that in the case of cultural evolution. I’m not saying it can’t happen. I’m asking for why you think it has already happened.Finally, you say: “Our distant ancestors became exceptionally good at suppressing disruptive self-serving behaviors within groups so that between-group selection became the primary evolutionary force, favoring teamwork in all its forms. That’s what our moral psychology is all about.” No, it most definitely isn’t! Those may have been the roots of moral instincts, but morality since the invention of religion, philosophy, and politics is a lot more complicated that just favoring teamwork. Which is why I argue that biology provides the boundary conditions for the emergence of culture, but that culture is its own beast, characterized by its own dynamics and modalities. Using the same tool to tackle widely diverse problems is simply not productive, like the proverbial guy who kept thinking that everything is a nail because he only had a hammer.
Massimo Pigliucci
Massimo Pigliucci