Monday, October 26, 2009

Svante Paabo believes modern humans & Neandertals interbred   posted by Razib @ 10/26/2009 02:20:00 PM

Neanderthals 'had sex' with modern man:
Professor Svante Paabo, director of genetics at the renowned Max Planck Institute for Evolutionary Anthropology in Leipzig, will shortly publish his analysis of the entire Neanderthal genome, using DNA retrieved from fossils. He aims to compare it with the genomes of modern humans and chimpanzees to work out the ancestry of all three species.
Paabo recently told a conference at the Cold Spring Harbor Laboratory near New York that he was now sure the two species had had sex - but a question remained about how "productive" it had been.

"What I'm really interested in is, did we have children back then and did those children contribute to our variation today?" he said. "I'm sure that they had sex, but did it give offspring that contributed to us? We will be able to answer quite rigorously with the new [Neanderthal genome] sequence."

The way Paabo is couching it, what he has found then seems likely to be evidence that humans who had just expanded Out of Africa contributed to the genomes of Neandertals. In other words, modern human introgression into Neandertals. Of course if the gene flow was from modern human to Neandertals exclusively, then it would be an evolutionary dead end since that lineage went extinct.


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Wednesday, September 05, 2007

Contamination in Neandertal DNA   posted by p-ter @ 9/05/2007 07:52:00 PM

Almost a year ago, Svante Paabo's group published an article reporting a million base pairs of DNA isolated, in principle, from Neandertal bone. The results were striking, in that Neandertals appeared much closer, genetically, to humans than one might expect. Well, Nature News has an article this week about a paper in PLoS Genetics arguing that the reason for this could actually be quite parsimonious: contamination from modern humans. From the news report:
Svante Paabo, senior author of the Nature paper, concedes that his group at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, had problems with contamination. These prompted him to change laboratory procedures and to add controls late in 2006, after the paper was published. "I agree with [Wall's] analysis," Paabo says. "Their observations are formally correct."
The paper estimates the amount of contamination at about 80%, which is pretty atrocious. The irony here, of course, is that Paabo was one of the people who made sequencing ancient DNA feasible again after fiascoes like reports of "dinosaur DNA"-- the "dinosaur" sequences ended up matching up pretty well with some of the lab members, and it appears Paabo has made the same mistake here. Fortunately, this is likely only to be a minor setback--the other group working on the DNA seems to have avoided the contamination problems, and presumably Paabo's most recent work will be more careful about it.

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