Much of the discussion about human biology and evolution thus far has focused on the adult organism. Biological individuals do not arise full grown from the womb however, nor do they remain young adults forever. A full understanding of human biology requires an examination of ourselves throughout the life span. This life span approach to humans views the individual as undergoing change throughout his or her life, and these changes have repercussions for individual adaptation as well as for population-level concerns such as those related to demography. It is not sufficient to possess a genetic background that enables one to be a successful adult; one must adapt and cope as an infant, child, adolescent, and also when one reaches elderly status.