I am reading Tim Lewens’ new book Cultural Evolution (I am still halfway through it, so perhaps other posts will follow). One aspect I found interesting – and I imagine this will not come as a surprise to readers of this blog – is a peculiar conception of what identifies an approach to culture as “evolutionary”.
Lewens attacks the problem from a familiar perspective (see, for example, here), defining a taxonomy of possible evolutionary commitments for cultural explanations. As usual, some of them are too broad (Lewens calls them “historical” approaches), while others are too restrictive (he is skeptical of replication-based accounts of cultural evolution): things are more interesting in the middle.
A first difference in respect to what is, at least for me, a standard view (see for example this recent paper), is that Lewens considers the approach of Boyd, Richerson and colleagues as “not-selectionist”. In any case, this is not the topic of this post, and Lewens might have good arguments to defend the assertion that “claims about selection are only of secondary importance to them, given their primary motivation for taking an evolutionary perspective on culture” (p. 16). So what is this motivation? As Boyd and Richerson asserted in several places, biology is fundamentally darwinian because its explanations are rooted in population thinking, and cultural explanations are darwinian as long as they are rooted in population thinking too. This seems to be a quite uncontroversial position. Sperber and colleagues, which disagree on various points with Boyd and Richerson, nonetheless recently wrote (here):
We agree with Richerson & Boyd  that the overall general framework for the study and modelling of cultural evolution should be that of ‘population thinking’ (so named by Ernst Mayr, who described it as one of Darwin’s most ‘fundamental revolutions in biological thinking’ ).
They continue giving a somehow standard definition of what population thinking is, namely:
looking at a system (such as culture) as a population of relatively autonomous items of different types with the frequency of types changing over time. The types themselves are not defined by their ‘essence’ but as historical subpopulations, features of which may change over time.
Starting by saying that I am not an expert, the concept of population thinking (as used in cultural evolution) has actually always puzzled me, and reading this book perhaps helped me to understand why. As the story goes for biology, population thinking represented a potentially revolutionary, counter-intuitive, position against a typological/essentialist view of natural history. But what about social science? This is how Lewens defines population thinking (p.17):
the assumption that […] large scale patterns extending across time could be explained in terms of the aggregated effects of many small-scale events that occur in the lives of individual organisms.
While there are countless ways a social scientist can be against this assertion, clearly this has not much to do with “evolution”, and in fact Lewens draws an analogy with the kinetic theory of gases, where population-level features (e.g. temperature) are the aggregate outcomes of individual-level interactions, concluding that “there is no particular reason to call a populational approach ‘Darwinian’: we could just as well describe it as a kinetic theory of culture”, which is what he does indeed.
So what does remain of cultural evolution, if one is only committed with population thinking? While Levens can call these approaches “kinetic”, a big all-capitals “Cultural Evolution” is on the cover of the book. His idea is that these approaches combine population thinking with an adaptationist stance. In the case of Boyd and Richerson, this is the fact that social learning (and the general-domain mechanisms that implement it) is itself an adaptation, while in the case of Sperber it is a more general commitment to ‘standard’ evolutionary psychology to explain human cognition.
While this picture is mostly correct, it is, at least from my perspective, slightly intellectually unsatisfying. In my view, an evolutionary approach to culture should be committed to the idea of the process of cultural change being (broadly) darwinian. What are the options then?
- We accept that views of cultural change that are not committed to more than a general idea of population thinking are not, in fact, evolutionary.
- There is a way to define population thinking which is both coherent with what we know about cultural change and enough restrictive to justify the term cultural “evolution”.
- There is a way to define “evolution” interestingly, that is not related to population thinking, and that is well suited for culture.
- We adopt a view of cultural change in which selection, for example, has a strong enough role (not necessarily as strong as in biological evolution) to, again, justify the usage of the term cultural “evolution”.
- We use “evolution” in a broad sense (i.e. not implying analogies in the process)
As I mentioned, (5) is not very satisfying for me, but perhaps there are good pragmatic reasons to support something similar – and perhaps there are good pragmatic reason to not support (1). I’d be happy to know more about (2) and (3). I defended, indirectly, a version of (4) in this paper, and, if someone does not convince me of the contrary, I will probably remain on this position!