KEY CONCEPT Humans appeared late in Earth’s history.

1. KEY CONCEPT Humans appeared late in Earth’s history.

2. 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)

3. 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.

4. Humans share a common ancestor with other primates. • Primates are mammals with flexible hands and feet, forward-looking eyes and enlarged brains.

5. Prosimians are the oldest living primates. • They are mostly small and nocturnal. • Primates evolved into prosimians and anthropoids.

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

7. foraging • carrying infants and food • using tools • Walking upright hasimportant adaptiveadvantages. • Bipedal means walking on two legs.

8. 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.

9. Australopithecus afarensis Homo habilis Homo neanderthalensis Homo sapiens 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. 200,000 Years Ago- Present 200,000-30,000 Years Ago 2.4-1.5 MYA 4-3 MYA Brain volume: 1300 cm3 Brain volume: 700 cm3 Brain volume: 1500 cm3 Brain volume: 430 cm3

10. 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

11. 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.