Aaron A. Sandel, Department of Anthropology-University of Michigan

Strong social bonds, or “friendships,” play an important role in primate behavior. These bonds feature prominently in the lives of adult male chimpanzees. Male chimpanzee friends form coalitions, share food, join each other on territorial border patrols, and help each other as they attempt to rise in the dominance hierarchy. Despite the importance of friendship and dominance rank in adulthood, scant information exists regarding how they develop. Do friendships form early in life? Do males start to jockey for position in the dominance hierarchy before they reach adulthood? For one year, I observed male chimpanzees transitioning to adulthood at Ngogo in the Kibale National Park, Uganda. In contrast to adults, adolescent male chimpanzees do not compete for status with their peers. Instead, they prioritize affiliative relationships. Adolescent males form social bonds with maternal brothers, as do adult males. In contrast to middle-aged adult males, however, adolescent and young adult males forge some of their strongest bonds with old males rather than peers. Unexpectedly, some of these old males are their fathers. Because chimpanzees mate promiscuously, there is no reason to suspect that young male chimpanzees can recognize their fathers or that fathers can recognize their sons. These findings raise the intriguing possibility that fatherhood may have evolved from an ape-like social system.