Visual Kin Recognition in Nonhuman Primates (Pan troglodytes and Macaca mulatta) Inbreeding Avoidance or Male Distinctiveness?

Faces provide important information about identity age and even kinship A previous study in chimpanzees reported greater similarity between the faces of mothers and sons compared with mothers and daughters or unrelated individuals This was interpreted as an inbreeding avoidance mechanism where females the dispersing gender should avoid mating with any male that resembles their mother Alternatively male faces may be more distinctive than female faces biasing attention toward males To test these hypotheses chimpanzees and rhesus monkeys matched conspecifics faces of unfamiliar mother and fathers with their sons and daughters Results showed no evidence of male distinctiveness rather a cross gender effect was found chimpanzees were better matching moms with sons and fathers with daughters Rhesus monkeys however showed an overwhelming bias toward male distinctiveness They were faster to learn male faces performed better on father-offspring and parent son trials and were best matching fathers with sons This suggests that for the rhesus monkey Inbreeding avoidance Involves something other than facial phenotypic matching but that among chimpanzees the visual recognition of facial similarities may play an important role