Primate Adaptation and Evolution Taxonomic order of mammals that includes prosimians (lemurs), monkeys, apes, and humans. Estimated 230-270 species. Primates are diverse but share common features.

Common Characteristics Vision is dominant sense. Eyes face forward rather than to the side as in other mammals. Light-sensitive cells of retina packed closely together results in good vision. Eye position enables depth perception and gauging distances known as stereoscopic vision. Color vision.

More Characteristics Arboreal or tree-dwelling. Adaptations for survival in trees. Flexible shoulders and hip joints for locomotion, climbing, and swinging from branch to branch. Shoulders adapted for arm movement in different directions. In some species, such as apes, ball-and-socket shoulder joints provide mobility. Flexible elbows, allow palm of hand to turn in many directions. Hands and feet have nails rather than claws as seen in other mammals.

More Characteristics Hands used for food manipulation or grasping objects due to flexible or opposable thumbs. Rounded head and flattened face compared with other animals. Relative to body size, largest brain of any terrestrial mammal. Large brain size related to cerebrum, part of the brain involved in thinking and memory. Complex brain reflected in diverse behaviors and social interactions.

Primate Origins Earliest identified primate from fossil record is Purgatorius that lived about 60 to 65 million years ago. No living species like Purgatorius but prosimians come close. Notice the tail. Primates divided into two sub groups: prosimians and anthropoids.

Prosimians Small bodied. Include lemurs and tarsiers. Found in Africa and Southeast Asia. Nocturnal. Have large eyes to spot insects in the dark. Fossil evidence: prosimians evolved about 50 to 55 million years ago.

Three Major Anthropoids New World monkeys of South and Central America. Old World monkeys of Africa, Asia, and Europe. Hominoids: Asian and African apes and humans. More complex brain than prosimians - increased intelligence.

New World Monkeys Live in rain forests South and Central America. Include marmosets, capuchins, howlers, sakis, and spider monkeys. Live in trees (arboreal). Endangered – deforestation. Long, muscular prehensile tail (used to grasp and wrap around branches like another arm or leg).

New World Monkeys First anthropoids to evolve. Range in size from 6 inch pygmy marmoset to 3 foot howler monkey. Wide nostrils, circular, spaced apart. Fossils date back 30 to 35 million years.

Old World Monkeys Found in hot, dry environments (Africa) and cold environments (Japan). Both arboreal and live on the ground. Colobus, baboons, macaques, mandrills, proboscis monkeys. No prehensile tail. Fossils date back 20 to 22 million years.

Old World Monkeys Larger than New World monkeys. Narrow downward pointing nostrils. Longer hind legs than forearms. Flattened nails on fingers and toes. Prominent buttock pads. Tails, not prehensile, used for balance. Diurnal rather than nocturnal. Divided into subfamilies. Cheek-pouched monkeys and leaf-eating monkeys.

Hominoids Bipedal (walk on two legs ). To move efficiently on the ground Include Asian and African apes, humans, and direct ancestors. Theory: between 5 to 8 million years ago in Africa, hominoids diverged into 2 lines that eventually became chimpanzees and humans. Environmental change caused some hominoids to leave the trees and move to the ground to find food. No fossil support but DNA of humans and chimpanzees is similar.

Ape Characteristics Orangutans, chimpanzees, gibbons, bonobos, and gorilla. Long, muscled arms and legs for climbing and walking. No external tail. Arboreal or live on the ground. Capable of social interaction. Chimpanzees most closely related hominoid to humans.

More Ape Characteristics Larger and heavier than monkeys. More upright body posture than monkeys. Broad chest; muscular forelimbs. Rely on vision rather than smell; shorter noses than monkeys. Large brain to body size ratio compared with other animals. Live in Africa and Asia. Fossils date back 37 to 40 million years.

Great Apes Smooth mostly hairless face ; round ears. No cheek pouches. Thumb shorter than fingers; opposable. Arms longer than legs and big toe is also opposable. Can walk bipedally. Can distinguish colors; rely mostly on vision and hearing rather than smell. Wide range of vocalizations and facial expressions. Intelligent, capable thinkers; able to problem solve and learn language.

Primate Hands and Thumbs Vary in structure and manipulative ability. Hand of tarsier has opposable thumb and slender fingers with adhesive pads adapted for grasping branches. Hands of orangutan adapted for swinging from branch to branch; fingers serve as hooks for hanging on branches and thumb is short to not get in the way. Hand of gorilla has longer, more opposable thumb than orangutan; fingers are shorter. Human hand most manipulative ability; long thumb more opposable ; fingers more dexterous and capable of free movements.  

Primate Matrix