Demography and cultural complexity

This paper begins by calling attention to a puzzling feature of our deep past: an apparent mis-match between morphological evolution in our lineage, including the expansion of our brain and neocortex, and changes in material culture. Three ideas might explain this mis-match. (a) The apparent mis-match is an illusion: change in material culture is indeed driven by biological evolution, but of a kind difficult to identify in the fossil record; (b) the mismatch is caused by the fact that material culture is sensitive to the social and demographic environment, not just the native cognitive capacities of individual agents. Innovation and its uptake is more reliable in larger social worlds. (c) The mis-match is made possible by adaptive phenotypic plasticity; in particular, cognitive plasticity. Just as material culture evolves through cumulative cultural learning, so too do cognitive skills, including ones which make innovations in, and the transmission of, material culture more efficient. This paper is targeted on the second of these ideas, and distinguishes three different versions of the view that increases in social scale support increases in the complexity of material culture. Those are: (i) cultural selection is more efficient in larger social worlds; (ii) larger social worlds support more specialisation, which in turn supports a more complex material culture; (iii) cultural learning is more efficient in larger social worlds. The paper argues that the first two of these pathways are probably more important than the third in explaining otherwise puzzling features of the archaeological and ethnographic record.