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.

• No buttock pads or cheek pouches.

• 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.

• Divided into subfamilies. Cheek-pouched monkeys and leaf-eating monkeys.

Hominoids • Bipedal (walk on two legs ).

• 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.

• To move efficiently on the ground while avoiding predators, humanoids evolved to become bipedal.

• 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