Male and female adult skeletons differ sufficiently for the sex of burials to be determined. Although the whole skeleton should be taken into account when determining sex, sexual dimorphism (differences in form between males and females) is most pronounced in the skull and pelvis. The latter is the single most reliable area, and hence should be given most weight in sex determination because differences here are directly related to functional differences between the sexes. In general the female pelvis is broader than the male. A narrow pelvis is more efficient for locomotion, but in females a broader pelvis is dictated by the fact that it forms the birth canal. Women with very narrow pelvises are more likely to experience potentially lifethreatening problems during childbirth; thus most researchers agree that the principal reason for the evolution of pelvic sexual dimorphism in humans and other primates is natural selection in relation to childbirth in females (discussion in Tague 1995).