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Africa climate history.
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[QUOTE]Originally posted by rasol: [QB] [QUOTE]Originally posted by Super car: [b]Earlier it was thought that Homo Sapiens Sapiens appeared around 150, 000 years ago. Further studies show that they may well have been around 200,000 years ago. In light of what you posted earlier (provided below), what should be said about the climatic conditions during 200,000 years and how this affects the evolutionary process of humans? [/b][/QUOTE] What should be said is that climate varies everywhere and the variations involve many complex interrelated cycles, which are in turn related to ocean currents, orbital axes variation, release of carbon dioxide from volcanos and many other phenomena. However, tropical regions such as Africa do not vary as wildly over time as do northerly climes such as North America or Europe. Europe and North America vacilate between being largely ice covered wastelands to milder more temperate zones. Africa varies largey in that the deserts, grasslands and rainforests spread, and retreat, with human populations expanding and retreating along with it. During the last wet phase about 10,000 years ago much of the sahara was fertile, with crocodiles, giraffes, lakes and substantial human populations as well. The drying of this area is likely one of the factors that caused populations to converge into the Nile Valley and also expand across the Levant. Populations in Africa respond to climate change primarily by migrating. The precursors of the indigenous somatic variations that exist in Africa today have existed for many 10's of thousands of years because the same range of climate variation has exited during this time, and repeated over and again. And of course this is notwithstanding the climatic constant of tropical solar radiation, to which native African dark skin tone is adapted. The situation in Europe could not be more different.... [i]About 24,000 years ago, the last ice age began, with mountain-sized glaciers moving across most of Europe. Paleolithic Europeans retreated before the ice, finding refuge for hundreds of generations in three areas: what is now Spain, the Balkans and the Ukraine.[/i] - PA Underhill. [This message has been edited by rasol (edited 15 March 2005).] [/QB][/QUOTE]
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