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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.