The effect of spatial environmental heterogeneity on hominin dispersal events and the evolution of complex cognition

by Colin David Wren

Institution: McGill University
Department: Department of Anthropology
Degree: PhD
Year: 2015
Keywords: Anthropology - Anthropology Archaeology
Record ID: 2058041
Full text PDF: http://digitool.library.mcgill.ca/thesisfile130251.pdf


Modern humans are unique in the vast geographic range we inhabit. However, how, why, and under what conditions humans and our hominin ancestors successfully dispersed and settled throughout the world is still poorly understood, and presents one of the biggest challenges to understanding our evolutionary history. Increasingly sophisticated hominin cognition is assumed to play an important role in major dispersal events but it is unclear what that role is. This dissertation uses a series of agent-based models to explore the close relationship between cognitive complexity, the spatial heterogeneity of the landscape, and dispersal potential and velocity. Since dispersal is the global scale product of local scale mobility, the first agent-based model evaluates the role of cognitive complexity in the foraging related mobility of small foraging groups. As a proxy for cognition, model foraging groups, or agents, possess a variable accuracy of assessing the quality of their local environment as they decide where to move to maximize resources. The model results show that the spatial heterogeneity of the resource landscape exerts a selective pressure such that lower cognition is adaptive in low heterogeneity landscapes, and higher cognition is adaptive in high heterogeneity landscapes. In the models, cognition preferentially directs movement towards known resources, and indirectly inhibits dispersal outwards into unknown landscapes. This suggests that increased cognition could have inhibited hominin dispersal, and that the dispersal events that did occur likely came from low heterogeneity environments. The second section of this dissertation evaluates the robustness of these findings in two new models by extending how foraging groups acquire knowledge of their environment before making mobility decisions. The first varies the size of the agent's resource assessment area, and the second allows agents to learn about the resource landscape through social interactions instead of direct observation. In each case, low levels of environmental knowledge are advantageous, particularly in low heterogeneity environments. This adds further support to the hypothesis that hominin dispersals likely originated from a low heterogeneity environment, as this would have favoured the evolution of the low cognition hominins that had the highest dispersal potential. The final section of the dissertation combines the model of cognitive dispersal with the wave of advance model. The model quantifies the impact of cognition on dispersal velocity and wave pattern. The results show that the greater the level of cognitive complexity, the slower the wave of advance. Increased heterogeneity of the environment further decreases wave velocity when cognition is involved in mobility. Random movement, i.e. non-cognitive mobility, provides the highest velocity across almost all landscapes. This suggests that previous research has either overestimated the importance of cognition in facilitating dispersal events, or has grossly underestimated the rate of population…