Unlike animals in other mammalian orders, primates are not characterized by one or more conspicuous trait. Instead, primates are best defined in terms of their adaptability; which may be thought of as a response to the arboreal habitat and insect predation. Among the most significant diagnostic features of the order are a grasping big toe, a grasping big thumb that is opposable in many groups, digits ending in nails and tactile pads, pentadactylism, and retention of the clavicle. Among primates, the olfactory sense has been reduced along with the skeletal apparatus for smell and the olfactory areas of the brain. The sense of vision has become predominant; primates see in color and possess stereoscopic vision.

During the prenatal period, the primate fetus is nourished through a hemochorial placenta in which the fetal blood vessels are bathed in the maternal blood. The primates are characterized by the prolongation of gestation, during which the fetus grows rapidly, as well as by a long childhood period and a prolonged life span. Other characteristics of the order include the retention of a relatively unspecialized dentition, increased brain size, adjustment through learned patterns of behavior, and life in social groups.

This chapter introduced the various primate groups in anticipation of the chapters to follow. The Order Primates is divided into three suborders. The first, Prosimii, includes the lemurs, sifaka, aye-aye, lorises, and galagos. The second, Tarsioidea, contains the tarsiers. The final suborder, Anthropoidea, includes New World and Old World monkeys, apes, and humans.

I. Students should know the characteristics that define the Order Primates.

II. Students should understand the differences between the three Suborders of Primates: the Prosimians, Tarsiers, and Anthropoids.

III. Students should be able to distinguish between Old World and New World monkeys.

IV. Students should know the differences between apes and monkeys.

V. Students should understand the position of humans within the primate order and know the characteristics of the hominids.