A team of scientists says it has succeeded for the first time in retrieving genetic material from bones of so-called Cro Magnons, 25,000-year-old European ancestors of humans living today. The DNA sequences they analyzed are like those of modern humans and very different from those of Neandertals, consistent with the notion that there is little or no Neandertal blood in the human heritage.
The prevailing "out of Africa" hypothesis holds that modern humans emerged from Africa a few hundred thousand years ago and replaced other hominids including Neandertals. A competing "multiregional hypothesis" holds that Neandertals weren't all that different from modern humans and probably interbred with them. The Neandertals died out about 30,000 years ago. Geneticist Svante Pääbo was the first scientist who succeeded in extracting mitochondrial DNA (mtDNA) from Neandertal remains (ScienceNOW, 10 July 1997 ), but no one had analyzed DNA from Cro Magnons.
A group led by David Caramelli of the University of Florence, Italy, extracted and analyzed segments of mtDNA from the bones of two people--a teenaged boy and a young woman--that had been found in Paglicci Cave, a paleolithic site in southern Italy. The scientists took every possible precaution to avoid contaminating the samples with modern genetic material: DNA was extracted in a lab exclusively dedicated to such work, for example, and samples were analyzed in labs in both Spain and Italy. Horse bone DNA from the same site was also analyzed to be sure it contained no human DNA. The DNA sequences from the Paglicci specimens fell "well within" the range of variation of modern humans, and "differ sharply" from findings on three Neandertals that have been published so far, the authors report online in the Proceedings of the National Academy of Sciences this week.
Some scientists are thrilled at the results. This work is "another nail in the coffin" of the multiregional hypothesis, says Stanford University anthropologist Richard Klein. But others point out that it's impossible to be 100% certain whose DNA they've got. Fred Smith of Loyola University in Chicago, who is sympathetic to multiregionalism, says that despite all the precautions the authors took, "no protocol exists that will prove these sequences are authentically ancient DNA and not more recent contamination."
More about the Paglicci site