Origin of the human canine: A new solution to an old enigma

Abstract

Comparative dental data derived from 60 anthropoid species and observations of naturalistic behavior can be used to construct a selection model which accounts for the size and morphology of the three classes of canines (adult male, adult female, and deciduous) in these taxa. According to the model, in virtually all living anthropoids, two forms of selection impinge on canine size and form. One is related to the tooth's use as a weapon; the other is related to its use as an incisor. Selection related to the use of canines as weapons is heterogeneous among the three classes while incisal selection is homogeneous. The extent to which canines are designed for weapon or incisal usage depends on the evolutionary value of weapon use relative to incisal use. In most anthropoids, there is incisal selection operating on male canines but they exhibit few incisor-like traits because their evolutionary value as weapons is greater. The same incisal selection operates on female and deciduous canines but they exhibit many incisor-like traits because their evolutionary value as weapons is lower. The size and morphology of adult male and female and deciduous human canines since the Pliocene reflect a relatively high evolutionary value for incisal usage in all three classes of individuals. The evolution of proximate causes which led to the origin of the human canine is likely to have involved minor genetic and developmental changes. © 1992 Wiley-Liss, Inc.