Considerable biological and behavioral variation exists among living primates. Chapter 6 deals with variation within the Order Primates, and further refines the general discussion of primate characteristics from the previous chapter. Consideration is given for the best way to classify living hominoids including anatomical and behavioral characteristics, together with genetic and evolutionary relationships.

The chapter begins with a discussion of the traditional primate suborders of prosimians and anthropoids. An alternative classification scheme discussion illustrates classification difficulties. The Old and New World monkeys are also reviewed. Hominoid characteristics and classification follows, and reveals the need to consider the importance of evolutionary relationships between species. Such an approach more accurately identifies physical and biological similarities and differences and helps explain these relationships.

The chapter concludes with a detailed survey of the living apes. Their distribution, social structure, and physical characteristics provide a window toward our understanding of both our genetic and behavioral connectedness to them and to the hominin fossil record in future chapters.