What Is a Primate?

What characteristics do all primates share?

Primates, including lemurs, monkeys, and apes, share several adaptations for a life spent in trees. In general, a primate is a mammal that has relatively long fingers and toes with nails instead of claws, arms that can rotate around shoulder joints, a strong clavicle, binocular vision, and a well-developed cerebrum. The lemur in Figure 26–14 shows many of these characteristics. DOL•64

Fingers, Toes, and Shoulders Primates typically have five flexible fingers and toes on each hand or foot that can curl to grip objects firmly and precisely. This enables many primates to run along tree limbs and swing from branch to branch with ease. In addition, most primates have thumbs and big toes that can move against the other digits. This allows many primates to hold objects firmly in their hands or feet. Primates' arms are well suited for climbing because they can rotate in broad circles around a strong shoulder joint attached to a strong clavicle, or collar bone.

Binocular Vision Many primates have a broad face, so both eyes face forward with overlapping fields of view. This facial structure gives primates excellent binocular vision. Binocular vision is the ability to combine visual images from both eyes, providing depth perception and a three-dimensional view of the world. This comes in handy for judging the locations of tree branches, from which many primates swing.

Well-Developed Cerebrum In primates, the “thinking” part of the brain—the cerebrum—is large and intricate. This well-developed cerebrum enables more-complex behaviors than are found in many other mammals. For example, many primate species create elaborate social systems that include extended families, adoption of orphans, and even warfare between rival troops.

FIGURE 26–14 Primate This lemur displays several primate characteristics—it has flexible fingers and toes, arms that can rotate in broad circles around the shoulder joint, and forward-facing eyes that allow for binocular vision.