The emergence of the genus Homo is widely linked to the colonization of "new" highly seasonal savannah habitats. However, until now, our understanding of the possible impact of seasonality on this shift has been limited because we have little general knowledge of how seasonality affects the lives of primates. This book documents the extent of seasonality in food abundance in tropical woody vegetation. It then presents a systematic analysis of seasonality's impact in food supply on the behavioral ecology of non-human primates and ultimately applies its conclusions to primate and human evolution.