Expansion of the Genus Homo

The origin of the genus Homo has been traced to Africa. It is associated with brain enlargement, the acquisition of culture, a reduction in the emphasis of mastication as a means of food preparation, and the development of a bipedal gait. Species of the genus include H. habilis, H. erectus, and H. sapiens. The earliest fossil evidence of these hominids has been found in East Africa; namely, in and around the Olduvai Gorge, Tanzania.

The most primitive species of the genus, Homo habilis, differentiated itself from the Austalopithecus hominid lineage during a major cladogenetic event which occurred about 2.5 to 2.3 million years ago. This event involved an explosive period evolution coinciding with an episode of significant global climatic change. As ice sheets in Antarctica and the Northern Hemisphere underwent an expansion, cooler and drier conditions in Africa led to a reduction of wooded areas and the return of widespread open grasslands. South Africa's fossil record shows that these major changes in fauna resulted in widespread extinctions and the development of many new species.

For example, the muskox group suddenly disappeared, only to be replaced by about 20 new species of antelope. Similar changes occurred in the species that gave rise to man. At some time before 2.0 million years ago, Homo habilis appeared. Then, at a later date, H. habilis was followed by, yet another evolutionary advance, the species, Homo erectus. Although the extent to which th

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ation suffering from the condition increase southward. Furthermore, while in Southwest Asia and North Africa some malabsorption occurs, only in western Europe is the condition generally uncommon. These trends can be associated with milk consumption. People with a long tradition of consuming large quantities of milk tend to have lower prevalences of malabsorption. In addition, a population's lactase characteristics follow its migrations and are affected by interbreeding with outside groups. Another characteristic which is related to the location of a group's ancestral homeland is skin color. In Africa and Eurasia, coloring seems to correspond to latitude. Populations of darkest color generally to inhabit equatorial and adjacent areas. As one proceeds north though, into North Africa and the Mediterranean region, coloration becomes lighter. Finally, in Europe and beyond, people tend to be Caucasian. Of course, these generalizations don't apply on a global scale. The populations of India, Asia, and the indigenous people of the Americas are all intermediate shades. Furthermore, the aboriginal people of Australia are black. Nose shape is more difficult to associate with geographic location. It can be said that the indige

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