MULTIREGIONAL HYPOTHESIS

=Multi-Regional Hypothesis= [image:http://i.imgur.com/gYgtwJZ.png?3] This theory proposes that ''heidelbergensis'', the ''Neanderthals'', the ''Denisovans'' and archaic ''sapiens'' were all members of the same species. For instance, it proposes that the Neanderthals should be classified as ''Homo sapiens neanderthalensis'' -a sub species of ''Homo sapiens''. The theory argues that these groups represent regional variants of the same species much like the different ethnic groups observed today. This theory suggests that erectus left Africa, and ultimately evolved into ''Homo sapiens'' in Africa, Europe, and Asia simultaneously. Regional subspecies such as the Neanderthals developed, but they were all still ''Homo sapiens''. The different populations in each geographical area all contributed to the development of anatomically modern ''H. sapiens sapiens''. Gene flow (interbreeding) between each ensured that they did not develop into distinct species, but rather they simultaneously developed into the modern ''H. sapiens sapiens'' we are today. ==Supporting Evidence:== '''Fossil Evidence:''' Some scientists argue that certain fossil finds represent intermediates between erectus, Neanderthals and modern sapiens. They argue that the physical differences between these groups represent regional differences. For instance, some modern cold-adapted populations have features similar to the Neanderthals. They argue that many fossil finds cannot easily be classified as belonging to one group or the other because they are regional variants of a single species. '''Mitochondrial DNA:''' While the mtDNA from Neanderthal remains are substantially different from modern human in some cases the differences are less than those observed between chimpanzee subspecies. Some scientists suggest this could mean that the Neanderthals were different subspecies, but still belong to the same species as anatomically modern humans. '''Y-Chromosome:''' While an analysis of both mtDNA and Y-chromosomes sequences both suggest an African origin, the results were not entirely consistent, suggesting there are still flaws in our understanding and the data may not be conclusive. Also Y-chromosome analysis indicated a later expansion back into Africa from Asia, demonstrating there was gene flow (interbreeding) between regions and in both directions. '''Other Genetic Evidence:''' Analysis of some sequences on the X-chromosome suggest a much earlier African origin more consistent with the departure of ''Homo erectus'' from Africa. There is also some genetic evidence that gene flow (interbreeding) was not geographically limited. A recent African origin would have seen gene flow out of Africa, but there is also evidence of gene flow from Eurasia back into Africa.