The Anatomical Basis of Aggression in Hominins

Our thesis, that humans are at some level anatomically specialized for physical aggression, is based on two premises. First, although humans are arguably the most empathic and cooperative species on the planet, we also have a real problem with violence. Second, to the extent we can find ways to reduce aggression, intolerance, and violence in the future we should do so. As scientists, we know that the best solutions to our most important problems stem from understanding. Evidence that human aggression is partially tied to male contest competition (i.e., mating competition through the use of force or threat of force) comes from a growing number of subfields within evolutionary anthropology: primatology, archaeology, population genetics, sexual selection theory, and evolutionary psychology. I believe the field of comparative physiology can also contribute to a better understanding of the evolutionary basis of human violence by (1) determining if the anatomical and physiological characters that are known to distinguish hominins from the other great apes actually improve fighting performance, and (2) assessing the extent to which these characters are expressed differently in males and females, i.e., are sexually dimorphic. In this presentation, I will present results from two experiments we have done to test the controversial hypothesis that hominins are anatomically specialized for fighting by punching with a clenched fist. Our results are consistent with the suggestion that selection on male contest competition played a role in the evolution of the shape of the human hand and the pronounced difference in upper body strength observed between human males and females. Thus, our results add to a growing body of evidence suggesting that the evolutionary roots of much of the aggression, intolerance, and violence that plagues modern societies ultimately lies in the selection that shaped our mating system. Acknowledging and understanding the legacy of male interpersonal and group aggression can help guide policy directed at reducing violence in the future.