That, at least, is the implication of a new ancient DNA study my partner on Science's anthropology beat, Ann Gibbons, reports about today on our ScienceNOW online news service. The link is free for four weeks from today, so please click on it right away. The gist of the story is that an Italian team has sequenced mitochondrial DNA (mtDNA) from 28,000 year old Cro-Magnon bones, and that it does not show any similarities to Neandertal mtDNA previously analyzed. Cro-Magnons were modern humans, Homo sapiens, and lived in Europe around the time that Neandertals were on their way to extinction. Nevertheless, there were thousands of years of overlap between the two groups (most experts today consider them separate species), and it is possible that some of them interbreeded. While Neandertal DNA does not resemble that of people living today it is always possible that Neandertal sequences in the modern human genome were lost over time.
Here is the key paragraph:
In the new study, Caramelli's group isolated mtDNA from a different set of Cro-Magnon remains that had been found in the same cave in 2003. This time, only seven people handled the fossils, and the researchers verified that their DNA did not match that of the purported Cro-Magnon sequence. "In this case, we knew all the people that touched the bones," says team member Guido Barbujani, a population geneticist at the University of Ferrara, Italy. The team also had the work independently replicated, asking a lab in Spain to extract and analyze mtDNA from different splinters of skull and long bones. The upshot is that the Cro-Magnon mtDNA matches that of modern humans and does not contain patterns found in Neandertal mtDNA, the team reports online today in PLoS ONE. That result argues against the inbreeding hypothesis, says Barbujani. [[Note that the paper is available free at the "team reports" link]]
But the jury is still out, as Ann says. She quotes an ancient DNA expert who is still concerned about the pervasive problem of modern contamination in ancient DNA sequences.
Credit: Illustration by Knut Finstermeier; Neanderthal reconstruction by the Reiss-Engelhorn-Museum Mannheim