ABSTRACT
This chapter discusses the costs to the parent of reproduction and the benefits to be gained in the currency of its offspring. It reviews the kinds of energetic stresses that affect reproducing mammals, along with the solutions to these stresses that different animals have developed. Alter-natively, observations of parental interactions with young animals may touch one's emotions, and one might want to know more about the biological basis of such behaviors. Variation in human reproductive patterns may be less surprising if one is familiar with the variation in these patterns among other animals. While most biologists have seen the advantage of using the powerful conceptual tools forged by this new generation of evolutionary thought, most social scientists have not used these concepts to their advantage. One of the most difficult questions in biology is why a reproductive life span exists at all, for it is not obvious why young mammals delay their reproduction or why old animals cease to reproduce.
