12.6 Primate Evolution

KEY CONCEPT Humans appeared late in Earth’s history.

12.6 Primate Evolution

• SC.912.L.15.10* Identify basic trends in hominid evolution from early ancestors six million years ago to modern humans, including brain size, jaw size, language, and manufacture of tools. (MODERATE)

12.6 Primate Evolution

Common misconception

• Humans are descended from Modern Apes

Correcting the misconception

• Humans did not descend from modern apes.• Humans and African apes(gorillas and chimpanzees) descended

from a common ancestor that lived approximately 6-8 million years ago.

• The ancestor’s descendants diverged into two lineages: one gradually evolved into gorillas; the other diverged into two lines, again about 5 million years ago, one giving rise to the ancestors of modern chimpanzees and the other leading to the early hominids.

12.6 Primate Evolution

Humans share a common ancestor with other primates.

• Primates are mammals with flexible hands and feet, forward-looking eyes and enlarged brains.

12.6 Primate Evolution

• Primates evolved into prosimians and anthropoids.

– Prosimians are the oldest living primates.– They are mostly small and nocturnal.

12.6 Primate Evolution

– They are subdivided into the New World monkeys, Old World monkeys, and hominoids.

– Anthropoids are humanlike primates.

– Homonoids are divided into hominids, great apes, and lesser apes.

– Hominids: primates that walk upright have long lower limbs, and thumbs that oppose and larger brains

– Hominids include living and extinct humans.

12.6 Primate Evolution

• Bipedal means walking on two legs.– foraging– carrying infants and food– using tools

• Walking upright hasimportant adaptiveadvantages.

12.6 Primate Evolution

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.

12.6 Primate Evolution

Modern humans arose about 200,000 years ago.

• Homo sapiens fossils date to 200,000 years ago.• Human evolution is influenced by a tool-based culture.• There is a trend toward increased brain size in hominids.

Australopithecusafarensis

Homo habilis Homo neanderthalensis

Homo sapiens

Brain volume: 430 cm3

Brain volume: 700 cm3

Brain volume: 1500 cm3

Brain volume: 1300 cm3

4-3 MYA2.4-1.5 MYA 200,000-30,000 Years Ago

200,000 Years Ago- Present

12.6 Primate Evolution

First thought to use cruel stone tools

• This is a skull of an adult Homo habilis male who lived about 2 million years ago. The part of the skull pictured here is about 5 1/2 inches tall. It was found at the Koobi Fora site in Kenya.

• Stone tools were found with skeletons

12.6 Primate Evolution

Our closest relative • Scientists have created a comparative map of

DNA sequences found in humans and chimpanzees, our closest relative. The map confirms previous estimates of the high degree of genetic similarity between the two species. In one of the largest comparisons of human and chimpanzee genomic sequence to date, the researchers calculated that the shared sequences were 98.77 percent identical.

• The researchers aligned some 77,000 chimpanzee DNA fragments to

corresponding segments of the human

genome sequence.