Cultural Network Structure

How did our society decide how much to count things like education and artistic taste when evaluating prestige and status? How did we pick key moral norms and values, such as democracy, gender equality, legal due process, rules of just war, and norms of good parenting? Yes, such choices are weakly influenced by our DNA, and also by cultural evolution selection pressures on individuals. But mostly these things came from cultural evolution of groups.

You may have heard that such *group selection* never happens, but that’s wrong. Not only do most cultural evolution scholars see group selection as a key force, group selection also seems to important in DNA evolution, where species are groups. The fact that more species today descended from fragmented habits like rivers, coral reefs, and rainforests, where habitats were smaller, suggests that group selection of species has actually mattered more for DNA than individual selection within species.

I’ve said previously that healthy cultural evolution for stuff like norms status markers depends on four key parameters: enough cultural variety, strong enough selection pressures on cultures, slow enough internal cultural drift, and slow enough rates of environmental change. But I have to admit that this first “variety” parameter is a sloppy way to talk about it. Counting the number of cultures would make sense if, as with species for DNA, there was only one clear scale at which people are joined into cultural groups. But in fact cultural behaviors cluster together at many different scales.

However, I’ve been doing some reading, and have found that for decades cultural evolution scholars have had a less-sloppy substitute concept: “network structure”. If you look at the details of who people interact with, and who they are likely to copy their behaviors from, the shape of the network of such ties matters a lot for cultural group selection.

For example, the network feature that most promotes group selection seems to be “modularity”, roughly how many more ties there are within clusters, compared to between clusters. It also matters how similar are people within clusters, how much overlap there is between interaction and emulation networks, how well prestige tracks adaptiveness, how much conformity pressure there is for a behavior, and how much that behavior effects visible outcomes that people care about.

Each different type of behavior can have its own different network, and its own different coordination scale, requiring group selection at that cluster scale or above in order to select adaptive versions of that behavior. But it seems clear that relevant scales for many kinds of behaviors have greatly increased over the last few centuries, greatly reducing the effective “variety” for the purposes of cultural evolution. And this is plausibly cutting the effect strength of group selection, likely enough to cause net maladaptive change to our norms and status markers.