Canine tooth size in female primates

AMONG mammals, weapons such as canine teeth or antlers are often more pronounced in males than in females1–5. Two reasons are normally proposed for such sexual dimorphism. First, there is more competition among males than among females for access to mates and, in consequence, there is enhanced selection for fighting ability6–9. Second, such weapons are important organs of defence for the male, who often assumes the role of defending his mates and offspring from predators9,10. In this paper, we discuss a third factor that is involved: selection acting to influence the size of weapons in females.