Nine primatologists — Richard W. Byrne, Robin I. M. Dunbar, William C. McGrew, Anne E. Pusey, Charles T. Snowdon, Craig B. Stanford, Karen B. Strier, and Richard W. Wrangham — consider the implications of primate behavior for understanding human evolution. Topics of the individual essays include reproduction, food and diet, tool use, intelligence, communication and language, and culture. "If you want a source that cogently discusses human intelligence in the context of the behavior of other primates," writes Ian Tattersall, "Tree of Origin is the place to turn."