12.6 Primate Evolution How did modern humans evolve?

KEY CONCEPT Humans appeared late in Earth’s history.

Humans share a common ancestor with other primates. Common ancestor of all primates probably arose before the mass extinction that ended the Cretaceous Period. Primates are mammals with flexible hands and feet, forward-looking eyes and enlarged brains.

Primates evolved into prosimians and anthropoids. Prosimians are the oldest living primates. They are mostly small and nocturnal. (lemurs) These are the tarsiers. Their physical appearance has changed little since their appearance 40 MYA.

Anthropoids are humanlike primates. They are subdivided into the New World monkeys, Old World monkeys, and hominoids.

New world monkeys are native to the Americas. Live in trees Have grasping tails

Old world monkeys are native to Africa. spend some time in trees, but spend much of the time foraging on the ground They have larger brains and can grasp things better.

Homonoids are divided into hominids, great apes, and lesser apes. Homonids include living and extinct humans.

Homonids walk upright, have longer lower limbs, opposable thumbs, and large brains Include all species in the human lineage, both modern and extinct. The skeletal changes required to walk upright can be seen in intermediate fossils between homonoids.

Bipedal means walking on two legs. Walking upright has important adaptive advantages. foraging carrying infants and food using tools

There are many fossils of extinct hominids. Most hominids are either the genus Australopithecus or Homo. Australopithecines were a successful genus. The Homo genus first evolved 2.4 million years ago.

Modern humans arose about 100,000 years ago. Homo sapiens fossils date to 100,000 years ago in Ethopia. Human evolution is influenced by a tool-based culture. There is a trend toward increased brain size in hominids. Australopithecus afarensis Homo habilis Homo neanderthalensis Homo sapiens