The Spatial Scale of Social Learning Affects Cultural Diversity

Sewall Wright's (1943) concept of isolation by distance is as germane to cultural transmission as genetic transmission. Yet there has been little research on how the spatial scale of social learning—the geographic extent of cultural transmission—affects cultural diversity. Here, we employ agent-based simulation to study how the spatial scale of unbiased social learning affects selectively neutral cultural diversity over a range of population sizes and densities. We show that highly localized unbiased cultural transmission may be easily confused with a form of biased cultural transmission, especially in low-density populations. Our results have important implications for how archaeologists infer mechanisms of cultural transmission from diversity estimates that depart from the expectations of neutral theory.

The Cultural Transmission of Great Basin Projectile-Point Technology II: An Agent-Based Computer Simulation

We present an agent-based computer simulation that extends a previous experimental simulation (Mesoudi and O"Brien 2008) of the cultural transmission of projectile-point technology in the prehistoric Great Basin, with participants replaced with computer-generated agents. As in the experiment, individual learning is found to generate low correlations between artifact attributes, whereas indirectly biased cultural transmission (copying the point design of the most successful hunter) generates high correlations between artifact attributes. These results support the hypothesis that low attribute correlations in prehistoric California resulted from individual learning, and high attribute correlations in prehistoric Nevada resulted from indirectly biased cultural transmission. However, alternative modes of cultural transmission, including conformist transmission and random copying, generated similarly high attribute correlations as indirect bias, suggesting that it may be difficult to infer which transmission rule generated this archaeological pattern. On the other hand, indirect bias out-performed all other cultural-transmission rules, lending plausibility to the original hypothesis. Importantly, this advantage depends on the assumption of a multimodal adaptive landscape in which there are multiple locally optimal artifact designs. Indeed, in unimodal fitness environments no cultural transmission rule outperformed individual learning, highlighting how the shape of the adaptive landscape within which cultural evolution occurs can strongly influence the dynamics of cultural transmission. Generally, experimental and computer simulations can be useful in answering questions that are difficult to address with archaeological data, such as identifying the consequences of different modes of cultural transmission or exploring the effect of different selective environments.