In the 1960s, Americans wrestled with Civil Rights struggles at home and the escalating Vietnam War abroad, not to mention the looming potential for nuclear violence. In this context, the aggression of humans appeared to distinguish us from all other animal species. Only humans were capable of murdering members of our own species, only humans were killer apes. Scientists began to argue that the horrors of WWII resulted not from some weird aberration of human nature, they were human nature. By the 1970s, aggressive competition between members of the same culture, community, even family had become a typical way of describing a universal human nature in evolutionary terms. In this paper, I discuss a series of headline-grabbing episodes from the summer of 1975, as the violence of the animal kingdom came to be seen as continuous with that of humanity. That summer, four Western researchers associated with Stanford University were kidnapped from Jane Goodall’s research center at Gombe National Park. Additionally, both male and female chimpanzees were observed killing members of their own species. These overlapping narratives of human and chimpanzee violence were at once political, territorial, and psychological. In their wake, characterizing the uniqueness of humans through our capacity to kill each other no longer seemed tenable. I use my discussion of these episodes to illustrate both the gendered character of natural violence in the 1970s and the increasing skepticism among some social scientists that explorations of aggression in animals could provide practical guidance for ameliorating violence in human societies.