Friday, May 01, 2009

Out of Africa Again

A story in Foxnews from the AP reports of a study in which it was found that Africans have the most genetic variability of any continental group studied. They write:
Africans have more genetic variation than anyone else on Earth, according to a new study that helps narrow the location where humans first evolved, probably near the South Africa-Namibia border.

The largest study of African genetics ever undertaken also found that nearly three-fourths of African-Americans can trace their ancestry to West Africa.

The new analysis published Thursday in the online edition of the journal Science.

"Given the fact that modern humans arose in Africa, they have had time to accumulate dramatic changes" in their genes, explained lead researcher Sarah Tishkoff, a geneticist at the University of Pennsylvania.

People have been adapting to very diverse environmental niches in Africa, she explained in a briefing.

This seems like another nail in the multiregional model of modern human origins. I need to see the study.


  1. This seems like another nail in the multiregional model of modern human origins.What does that model say?

  2. There are actually several variants. The classic Multiregional Evolution (MRE) model argues that modern humans arose out of local populations in several areas of the Old World but remained connected, through gene flow, to other populations such that speciation never occurred in any one area. This explains local traits in fossils series in different places in the Old World as well as what are perceived as in situ transitions. This is very simplified but that is the gist of it. Its most ardent supporters are Milford Wolpof and Alan Thorne.

    Another model is the assimilation model, put forth by Fred Smith, in which it is postulated that, while modern humans originated in sub-Saharan Africa, they mixed with the archaic Homo sapiens groups they encountered. Selection for more modern traits over time led to the modern genome appearing.

    The polar opposite of the multiregional model is the Recent African Evolution model (RAE), which posits that modern humans originated in Africa in a speciation event sometime between 140 and 280 Ky BP and replaced the archaic humans they encountered. This marshals DNA evidence such as that put forth in the article above.

    Right now the preponderance of evidence leans slightly toward the RAE model given the genetic evidence and the fact that groups like Neandertals seem to have survived until around 27 ky BP before dying out. The problem is that there are burials like Lagar Velho in Portugal from which the skeletal remains show transitional characteristics in an adolescent and some of the genetic studies done supporting RAE are somewhat equivocal. It is a very fertile area of research right now. That help?