Gallagher, EM; (2017) Evolutionary Models for the Origins of Agriculture. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The transition from hunting and gathering to farming at the end of the Pleistocene was one of the most important events in human history, having major impacts on human demography, evolution, health, culture, technology, and social stratification. The reasons why some societies switched to farming are still debated, with climate stabilisation and population pressure as popular hypotheses. However, since these processes occurred so long ago, investigating the transition can be difficult without the use of mathematical models. In this thesis I investigate the effect of various factors, including population size, conservatism, property rights, environmental conditions, climate variability, and mobility, on the transition to farming using evolutionary models. I do this by implementing an intensive parameter sensitivity analysis method on an existing game theoretical model (Bowles and Choi, 2013) for the origins of agriculture, and also develop and explore my own agent-based models of social and environmental interactions. Using the Bowles and Choi model, I find that the key parameters for the emergence of farming are group structuring, group size, conservatism, and farming-friendly property rights. The analysis of this model also shows that although advantageous, it is not essential for the emergence of farming for farming productivity to be greater than foraging productivity. In the development of my own model, I first consider mobility changes in a forager population, and find that low depletion and high growth rates can lead to reduced mobility, low fitness, and high population density. When I add subsistence behaviours to the model I find that three behaviours can evolve in response to different environmental conditions; mobile foraging, sedentary foraging, and sedentary farming. I also find a relationship between reduced mobility, the emergence of farming, decreased fitness and high population densities. Additionally, my model predicts that population pressure was caused by, but not causal of, the switch to farming. Importantly, these results concur with the observed archaeological data and ethnographic record, and highlight the value of using modelling to validate and/or challenge observed data.

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