Econstudentlog

The Origin and Evolution of Cultures (1)

(Smbc). The book is not really a book about economics, but I haven’t come across a similar comic with the words ‘mathematical anthropology’, or something along those lines, at the bottom and I think it’s close enough (besides I really love that cartoon).

I have talked about the book before on more than one occasion, as some of Boyd and Richerson’s results/ideas tend to naturally pop up in a lot of contexts when one is reading e.g. anthropology texts – and despite not having read the book I’ve been familiar with some of the ideas. I’ve considered it to be ‘a book I ought to read at some point’ for quite a while. I think Razib Khan said nice things about it at one point; given that I really liked a few of the other books he’s recommended I think that was what originally made me focus in on the book. I have long believed I would find the topic to be interesting as well as the suggested approach to dealing with the topic sensible; I have also, however, believed for a long time that the book would be a lot of work, which is part of what has kept me back.

I’ve now read enough, I think, to at least have an impression of what it’s about. It is, as expected, a technical book – there are quite a few remarks along these lines in the book:

“While we have not been able to solve (12) analytically, it is easy to solve numerically […] Because equation (13) is quite complex, we have not been able to derive an analytical expression for these equilibrium frequencies. However, it follows from the symmetry of the model that there is a stable symmetric equilibrium […] A more rigorous local stability analysis of the complete set of recursions supports the heuristic argument just given. Consider the set of i+1 difference equations where Δpj(j=0,1,…,i; see the Appendix) provides the dynamics of the behavioral traits at each stage. The cooperative equilibrium point […] is stable under the two distinct conditions …”

Someone ‘like me’ will not need to look up a lot of math-related stuff in order to understand the coverage in this book – the math is not that hard, it’s just that in some of the chapters there’s quite a lot of it. Then again if you’ve never seen a symmetry argument or people talking about deriving numerical solutions to troublesome analytical expressions (like the stuff above) before, and/or if you’ve never heard of eigenvalues or perhaps don’t have a good grasp of concepts like model equilibria or evolutionarily stable strategies, you’ll probably have some trouble along the way. One thing that ‘helps’ quite a bit in this context is that the math never seems superfluous; you get the clear impression that the authors did not add math in order to show how smart they are, but that they rather did it to promote and encourage a more systematic (…methodologically valid?) approach to this area of research. As they argue in the introduction:

“We think the way to make cultural explanations “hard” enough to enter into principled debates is to use Darwinian methods to analyze cultural evolution […] applying the evolutionary biologists’ concepts and methods to the study of culture […] Cultural evolution is rooted in the psychology of individuals, but it also creates population-level consequences. Keeping these two balls in the air is a job for mathematics; unaided reasoning is completely untrustworthy in such domains.”

I like their approach and I like the book so far. It has a lot of useful angles in terms of how to think about cultural stuff; variables, mechanisms, and tradeoffs.

I really liked the ‘Introduction’ chapter and before going any further I think I should a add a few (additional) remarks from that part of the book:

“People in culturally distinct groups behave differently mostly because they have acquired different beliefs, preferences, and skills, and these differences persist through time because the people of one generation acquire their beliefs and attitudes from those around them. To understand how cultures change, we set up an accounting system that describes how cultural variants are distributed in the population and how various processes, some psychological, others social and ecological, cause some variants to spread and others to decline. The processes that cause such cultural change arise in the everyday lives of individuals as people acquire and use cultural information. Some values are more appealing […] Some skills are easy to learn […] Some beliefs cause people to be more likely to be imitated […] We want to explain how these processes, repeated generation after generation, account for observed patterns of cultural variation.”

“Selection acting on culture is an ultimate cause of human behavior just like natural selection acting on genes. In several of the chapters in part III we argue that much cultural variation exists at the group level. Different human groups have different norms and values, and the cultural transmission of these traits can cause such differences to persist for long periods. The norms and values that predominate in a group plausibly affect the probability that the group is successful, whether it survives, and whether it expands.”

At the time the authors wrote the book they’d been working on this stuff for 30 years. The book is a collection of articles they’ve written over the years (not always together), so naturally some of the stuff – I don’t know how much as I have not looked for it – is available elsewhere; if you don’t want to read the entire book but would like to know a little more about the topic, you can probably find some of the stuff covered here in the book via google scholar; for example chapter 2 (‘Why Does Culture Increase Human Adaptability?’) in the book is as far as I can tell simply a reprint of this paper (pdf) – go have a look if you want to know what the book is like. Here’s chapter 10 (‘Why People Punish Defectors – Weak Conformist Transmission can Stabilize Costly Enforcement of Norms in Cooperative Dilemmas’ (pdf)). In the first case they put all the math in the back; as illustrated in the second link they don’t always do that. I’d rather link to those papers than cover them in detail here – go have a look if you’re curious.

The coverage in the book is really nice so far, and if the quality of the material does not drop later on I’ll certainly feel tempted to give it five stars.