Ian C. Gilby: Arizona State University

In order to understand the causes and consequences of the significant increase in meat consumption in hominins, we must first make inferences about the behavior of the last common ancestor (LCA) of apes and humans. Chimpanzees, which regularly hunt vertebrates, are a valuable point of reference for understanding the possible range of behavior exhibited by the LCA. I use long-term data from three communities in Tanzania and Uganda to determine why and how chimpanzees hunt. While chimpanzees exhibit a wide range of cooperative abilities, I will argue that in the context of hunting, cognitively complex mechanisms involving delayed, social benefits and/or shared intentions explain only a small proportion of the cooperation observed in the wild. Therefore, reliance upon such mechanisms in humans evolved after our lineage split from the great apes. Additionally, I will discuss the constraints on hunting faced by female chimpanzees, and will argue that similar factors provided a foundation for the evolution of the sexual division of labor in hominins.