Humans exhibit the longest period of infant dependency of any primate. The child’s prolonged dependence places the greatest burden on the mother, who is the main child caregiver in most societies. The burden of prolonged child care by human females may limit the kinds of work they can do. They may need the help of a man to do certain types of work, such as hunting, that are incompatible with child care. Because of this prolonged dependency, it has been suggested, marriage is necessary.13 But here the argument becomes essentially the same as the division-of-labor argument, and it has the same logical weakness. It is not clear why a group of women and men, such as a hunter-gatherer band, could not cooperate in providing for dependent children without marriage.