Ecology and Homo Sapiens
Ecological anthropologist Robert Foley points out that the savanna woodland of Africa 100¸000 years ago was an ideal environment for promoting the speciation of modern humans. He has studied monkey evolution in Africa and found that the widely dispersed populations had diverged¦ they did not continue on a single evolutionary course. Africa experienced considerable habitat fragmentation and reformation during the constant cold and warm cycles of the Ice Age¸ fluctuations that enhanced the prospects of speciation among the continent's animals and plants. For example¸ says Foley¸ one modern monkey genus alone radiated into 16 species at about the same time as modern humans evolved in Africa. Foley´s monkey studies have convinced him that modern humans evolved in just such a fragmented mosaic of tropical environments¸ developing distinctive characteristics that separated them from their archaic predecessors. There were areas where food resources were predictable and of high quality. In response to such regions¸ some human populations may have developed wide–ranging behavior¸ lived in larger social groups with considerable kin–based substructure¸ and been highly selective in their diet.
As part of these responses¸ some groups may have developed exceptional hunting skills¸ using a technology so effective that they could prey on animals from a distance with projectiles.With more efficient weapons¸ more advance planning¸ and better organization of foraging¸ our ancestors could have reduced the unpredictability of the environment in dramatic ways. Few archaeologists would be so bold as to associate ancient technologies with specific fossil forms¸ but we do know that tens of thousands of years later¸ Homo sapiens sapiens relied on much more sophisticated tool technology than their predecessors. The new tool kits were based on antler¸ bone¸ wood¸ and parallel–sided¸ stone–blade manufacture. This technology was far more advanced than anything made by their predecessors and took many millennia to develop. There is no question but that it would have conferred in major advantage on its user¸ both in terms of hunting efficiency and energy expended in the chase.
Interestingly enough¸ there are signs of technological change throughout eastern and southern Africa between 200¸000 and 100¸000 years ago¸ as age–old hand ax technology gave way to lighter tool kits that combined sharp stone flakes with wooden spear shafts¸ and to other more specialized artifacts used for woodworking and butchery. Such simple artifacts¸ made on medium–sized flakes¸ could have been archaic prototypes of far more efficent tools and weapons developed by anatomically modern humans after 100¸000 years. In addition¸ one must emphasize that the existence of such artifacts in Africa at the time when modern humans apparently first appeared there is not necessarily proof they were developed by Homo sapiens sapiens.
To summarize the controversey over modern human orgins–the weight of such evidenence as there is¸ and it is not much¸ tends to favor an African orgin for modern humans.
Out of Tropical Africa
If tropical Africa was the cradle of modern humans¸ how and why did Homo sapiens sapiens spread into Europe and Asia? The critical period was between 100¸000 and 45¸000 years ago. This is the date by which anatomically modern people were certainly living in southwest Asia. The only major barrier to population movement between tropical Africa and the Mediterranean Basin is the Sahara desert¸ today some of the driest territory on earth. Bitterly cold glacial conditions in the north brought a cooler and wetter climates to the desert before 100¸000 until about 40¸000. For long periods¸ the country between East Africa and the Mediterranean was passable¸ supporting scattered game herds and open grassland. The Nile Valley was always habitable¸ even during periods of great aridity in the desert.
Thus¸ small groups of modern people could have hunted and foraged across the Sahara into the Nile Valley and southwest Asia as early as 100¸000 years ago. From there¸ successors may have moved into south and southeast Asia at a still unknown date¸ but perhaps between 70¸000 and 50¸000 years ago¸ small numbers of modern people may have responded to population pressure and food shortages by moving across the wide land bridge that joined Turkey to southeastern Europe at the time¸ spreading into the homeland of the European Neanderthals within a few millennia.
With these still little known population movements¸ the initial radiation of modern humans throughout the Old World ended¸ perhaps by about 40¸000 years ago. As we shall see the next 30¸000 years saw the greatest of all human Diaspora take our ancestors into island southeast Asia¸ to New Guinea¸ Australia¸ Siberia¸ and¸ ultimately¸ the Americans.
