Assignment # 42: Notes: Human Evolution Scientific explanations for human origins.

Modern Thought on Human Origins All animals originate back to the Cambrian Mammals developed and diversified with the extinction of the dinosaurs (66 MYA) Primates are specialized tree mammals.

Primate Characteristics: Possess an opposable thumb. Reduced snout, stereoscopic vision. More single births, reduces the need for several offspring, allows for forebrain development. Parental care is extended, emphasis on learned behavior and social interactions.

Classification: Prosimians: most like the primitive tree shrews. Remain primarily arborous. Examples include: Tarsiers and Lemurs. Anthropoids: adapted more to grassland habitats. Examples include: New world monkeys, Old world monkeys, Hominoids.

Evidence for Classification DNA sequencing places humans more closely with apes. Oldest fossil evidence using radioactive dating places early hominoids in eastern Africa. This environment changes from forest to savanna. Physical structures change to fit this type of habitat.

Specific Hominoid Evolution Oldest form: Australopithecus ramidus (4.4 MYA). Shared similiarities between humans and apes. Australopithecus afarensis (3.18 MYA) Australopithecus africanus (southern Africa) Australopithecus boisei (eastern Africa) Australopithecus robustus Australopithecus aethiopicus

Red: A. afarensis, Green: A. boisei, Blue: A. africanus

Homo Descent Oldest known tool user: Homo habilis. The Homo genus is distinct from Australopithecus mainly upon cranium cavity size. Homo erectus (1.9 MYA) first to use fire, systematic game hunter, and use home bases.

Modern Human Descent Multiregional continuity hypothesis: each major region originated separately (Asia, Europe, Africa) Out of Africa hypothesis: Origins begin in Africa and other areas result from migration from there.

Homo sapiens neanderthalensis First found in the Neander valley, Germany. (200,000 years old) Large physical structured hominoid. Possess culture, maybe even religion.

Homo sapiens sapiens Cro-Magnons are modern humans. Thought to have entered Eurasia 100,000 years ago. Good tool developers. Possessed language, used written forms of communication. Very social and group structured.

What happened to Neanderthal? Two interesting theories explain the disappearance of Neanderthal. Warred to extinction. Gene pool was combined. The result is: Cro-Magnon is the modern human on earth today.

Conclusion to Notes: Copy the time line on page 580 (figure 32.4) carefully. Research on the internet the two theories of human descent. Provide an accurate citation of your sources, and a summary of each site’s content. Which theory do most modern scientists support?