Population density, mobility, and cultural transmission

Prompted by the results of a series of recently published simulation models, there is an increasing tendency for archaeologists to invoke demographic variables as explanations for changes in the sophistication or complexity of material culture. Whilst these models are undoubtedly valuable, this paper draws attention to persistent failings in the interpretation and application of these models by archaeologists. Despite having quite different effects, variables such as population size and population density are often used interchangeably; and whilst increasing mobility has an effect broadly equivalent to that of increasing population density, it is rarely given sufficient weight in archaeological explanations of cultural change. The analyses reported here develop a series of new simulations based on the ideal gas model, allowing for an explicit prediction of the encounter rate – the variable for which population density and mobility are proxies, and which ultimately governs the rate of cultural transmission. This model supports the predictions of earlier studies on the effects of population density and mobility, but suggests that population size will have no effect on rates of cultural transmission. These simulations are coupled with analyses that demonstrate a reciprocal correlation between population density and mobility in a large hunter-gatherer dataset. Given this correlation, it is argued that archaeological inferences about cultural transmission based on just one of these variables are unlikely to be valid. These findings are discussed in the context of previous research, and it is suggested that future studies would gain greater explanatory power by focusing explicitly on the social network structures likely to have characterised a particular archaeological population.