New research supports the belief modern humans came out of Africa in a single wave (led by a Moses?):
http://newsfeedresearcher.com/data/articles_t29/idt2007.07.19.07.26.10.htmlFrom the article:
"The team found that loss of genetic diversity was very closely mirrored by reduced physical variation the farther away people lived from Africa."
Of course this would be so even if humans descend from a single migration out of Africa in Homo erectus times. There is always less variation at the margins of a species' distribution because inbreeding and selection are greater. Genes from the centre or point of origin are also less able to reach all margins.
More from the article:
"Dr Andrea Manica and colleagues found all the skulls - 4,666 male and 1,579 female - bore striking similarities, giving support to the hypothesis that modern humans came fully developed out of Sub Saharan Africa"
If they all have a relatively recent common origin they should have more than "striking similarities", they should be almost exactly the same. Besides they would also have similarities if they had formed hybrids with any original population followed by selection.
I presume the genetic evidence they refer to is the mitochondrial DNA and Y-chromosome evidence I used in my "Adam and Eve" post. The following ancient SAGG link explains how these lines are reduced. Presumably the effect is not just confined to the period of modern humans:
http://www.scienceagogo.com/news/20040819224859data_trunc_sys.shtmlFrom that link:
"Scientists have puzzled over the fact that men's common ancestor, dubbed Y-chromosome Adam, seems to have lived around 100,000 years ago, whereas women's common ancestor, known as mitochondrial Eve, lived almost 200,000 years ago. Worldwide, the DNA from the Y chromosome has much less genetic variability than does mitochondrial DNA."
And this time more people are prepared to question the research:
http://anthropology.net/2007/07/21/anthropologists-dispute-latest-out-of-africa-claims/From this link:
"Hawks has written up some more thoughts on his blog, in which he gives vent to his frustrations at what he clearly perceives as being a study that is fatally flawed from the outset, but has nevertheless grabbed the headlines, as so many similar ’single exodus’ claims have done in the past."
Now SAGG readers are no doubt sick of my saying it's because the idea can be interpreted as fitting in with biblical stories. I agree with the final statement in this link:
"The idea that much of the Pleistocene was populated by people living in a technical and cultural coma, only wakened from their collective slumber in the Upper Palaeolithic by the sudden pinprick of a modern intelligence which arose from a single location at a specific point in time, (enabling the florescence of our über-selves), is itself long overdue for consignment to the compost heap of old theories based on out-moded concepts."