What is it about?

We review issues stemming from current models regarding the drivers of cultural complexity and cultural evolution. A currently popular model is the treadmill model that combines a simplistic view of cultural traits defined by the mode of transmission with the statistical fact that individuals with high skills are more likely to be found in a larger population than in a smaller population. However, to operate as claimed, the complexity of culture as being composed of idea systems is ignored and implausibly high skill levels must be assumed. Instead, when the complexity of artifacts made by hunter-gatherers is viewed from the perspective of the cultural idea systems involved in the conception, production and use of artifacts, we find that their complexity is explained by the risk hypothesis that relates the complexity of artifacts to the increased functional efficiency of implements. Empirically, all data on hunter-gatherer artifact complexity support the risk hypothesis and reject the treadmill model. Still, there are conditions under which increased technological complexity relates to increased population size, but the dependency does not occur in the manner expressed in the treadmill model. Instead, it relates to population size when the support system for the technology requires a large population size. If anything, anthropology and ecology suggest that cultural complexity generates high population density rather than the other way around.

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Why is it important?

Models such as the treadmill model that reduce culture to the mode of transmission do not take into account the richness of cultural systems as the basis for what makes us human and not just a smarter, more social ape, and are not just empirically invalid, but are misleading.


Good science depends upon developing theoretical models that have a solid, conceptual foundation and are in accord with empirical evidence. The treadmill model is defective in​ both accounts.

Dwight Read
University of California, Los Angeles

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This page is a summary of: Cultural complexity and complexity evolution, Adaptive Behavior, January 2019, SAGE Publications, DOI: 10.1177/1059712318822298.
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