ASB 194 lect13.doc

ASB 194 lect13.doc - Lecture 13. Emergence of Homo. During...

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Lecture 13. Emergence of Homo. During the time period from 3 mya to 2 mya there were 4 to 6 different species of Hominins in Africa. In some places two or three species lived in the same place at the same time. Thus we need to understand the radiation and eventual extinction of hominins during this period, and how this led to the Genus Homo. I. Late Australopithecenes specialized into a variety of niches. This led to three robust types, A. robustus (from South Africa) , A. Boisei (from Olduvai, Tanzania) and A. aethiopithecus (from Turkana, Kenya). All of these types have teeth and skull structures specialized for heavy chewing. They were found in Africa from 2.8mya to 1.4 mya. A) Robust Australopithecines have large jaws, huge molars, and a saggital crest for attachment of jaw muscles. B) Robust Australopithecines are about the same size as the gracile forms (females weigh about 70 lbs vs. 65 lbs for A africanus and A. afarensis). But they have larger brains (530 cc vs. 400-430 cc.). C). A aethiopithecus (the black skull) is hyper-robust and shows features intermediate with A. afarensis. It is the earliest robust (about 2.5 mya) and found in east Africa. A. boisei is a later super robust type of robust Australopithecene also found in east Africa. Some members of this species lived until 1.4 mya. A. robustus lived in Southern Africa at the same time as A. bosei lived in east africa. They had extremely large molars and thick enamel. D) For many years anthropologists believed that Robust Australopithecenes ate tough plant foods (seeds, nuts, roots, shoots), but recent chemical analyses of bones suggests they ate a good deal of meat. This means that they may have large molars only because of their dependence on hard plant foods during one season of the year. II Early Homo (habilis?) By 2.4 mya we find fossils that are strikingly different from the Australopithecines. They are present in east and south Africa until about 1.6 mya. These forms are often called Homo habilis (named by Louis Leakey in 1964 = “handy man”) but they may represent more than one species. They all share special features that allow scientists to classify them in our own genus 1) Homo habilis has a large brain (775cc) compared to Australopithecines. Their skull is more rounded and the face protrudes much less. 2) H. habilis has smaller teeth, thinner enamel, and a more rounded dental arcade than is found in Australopithecines. Note this is an evolutionary reversal-- chimps small molars thin enamel, Australopithecines large molars thick enamel, Homo
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small molars thin enamel again. Human dentition continues in this direction up to the present. 3) Some fossils with larger brain, larger molars, and longer legs are believed by
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This note was uploaded on 03/01/2011 for the course ASB 194 taught by Professor Hill during the Spring '11 term at ASU.

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ASB 194 lect13.doc - Lecture 13. Emergence of Homo. During...

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