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Ancient Man Had a Neanderthal Great-Great Grandfather and You Have Neanderthal DNA

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Analysis of the jawbone of a man who lived about 40,000 years ago reveals the closest direct descendant of a Neanderthal who mated with a modern 1) ___. Scientists know that modern humans and Neanderthals lived together in Europe and occasionally 2) ___. A modern human who lived in eastern Europe between 37,000 and 42,000 years ago had at least one Neanderthal ancestor as little as four generations back – which is to say, a great-great-grandparent.

 

Scientists have known for at least half a decade that living humans bear traces of Neanderthal blood – or more specifically, Neanderthal DNA. Just when and where our ancestors bred with their now-extinct cousins, however, has been tricky to pin down until now. A new study published last week in the journal Nature has the highest percentage of Neanderthal 3) ___ of any modern human ever studied. “We were lucky to hit upon an individual like this,“ says study co-author Svante Paabo of the Max Planck Institute for Evolutionary Anthropology in Leipzig. The specimen, known as Oase 1, consists only of a male jawbone, and from the moment it was discovered in 2002 its shape suggested that it might belong to a hybrid between Homo 4) ___ and Neanderthal. Those claims have remained controversial, but the new analysis lays the controversy to rest. “It’s really stunning,“ says Oxford’s Tom Higham, an expert on the Neanderthal-human transition who was not involved in this research. Part of what stuns Higham is the genomic artistry it took to tease useful genetic information out of the tiny DNA samples lead author Qiaomei Fu of Harvard Medical School and her team were able to extract from the 5) ___. “We tried to do this in 2009 and failed,“ says Paabo. His lab has been working since then to improve their techniques, with resounding success. The genome they sequenced from the samples was incomplete, but it was enough for the scientists to conclude that between 6% and 9% of Oase 1’s genome is Neanderthal in origin. People living today have 4% at most. That difference is more significant than it might seem. “We found seven huge pieces of chromosomes that seemed to be purely of 6) ___ origin,“ says Paabo. That means pieces had to come from a relatively recent ancestor, since they hadn’t yet been broken up by the reshuffling that happens in each generation as parents’ chromosomes combine.

 

 

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This jawbone from a 40,000-year-old modern human shows some Neanderthal features – and DNA now confirms he had a Neanderthal ancestor as few as four generations back. Photograph By Svante Paabo, Max Planck Institute For Evolutionary Anthropology

 

The non-Neanderthal genome sequences, meanwhile, show that Oase 1 isn’t related to humans living today. His genealogical line died out at some point. This analysis represents a biotechnological tour de force, but it also puts paleoanthropologists a step closer to fully answering to what Higham calls the $64,000 question: What happened to wipe out the Neanderthals, and when? Genomic analysis of a 45,000-year-old human thigh bone last year suggested that humans and Neanderthals interbred in what is now Siberia sometime between 50,000 and 60,000 years ago – an extremely imprecise number, and a very broad conclusion. “The great breakthrough here,“ Higham says, “is the ability to say ?this specific person had a Neanderthal great-great-grandfather.’ That puts a human timescale on it.“ If scientists can figure out when 7) ___ took place in different parts of Europe and the Middle East, they’ll be able to say in detail just how rapidly humans spread across these regions, how long they were in contact with Neanderthals. An analysis of a first draft of the Neanderthal genome by the Max Planck Institute team, led by Svante Paabo, released in May 2010, indicates interbreeding probably occurred.“Those of us who live outside 8) ___ carry a little Neanderthal DNA in us,“ said Paabo, who led the study. “The proportion of Neanderthal-inherited genetic material is about 1 to 4%. It is a small but very real proportion of ancestry in non-Africans today,“ says Dr. David Reich of Harvard Medical School, who worked on the study. This research compared the 9) ___ of the Neanderthals to five modern humans from China, France, sub-Saharan Africa, and Papua New Guinea. The finding is that about 1 to 4 percent of the genes of the non-Africans came from Neanderthals, compared to the baseline defined by the two Africans. This indicates a gene flow from Neanderthals to modern humans, i.e., interbreeding between the two populations. Since the three non-African genomes show a similar proportion of Neanderthal sequences, the interbreeding must have occurred early in the migration of modern humans out of Africa, perhaps in the 10) ___ East. No evidence for gene flow in the direction from modern humans to Neanderthals was found. Gene flow from modern humans to Neanderthals would not be expected if contact occurred between a small colonizing population of modern humans and a much larger resident population of Neanderthals. A very limited amount of interbreeding could explain the findings, if it occurred early enough in the colonization process. Sources; National Geographic; Wikipedia; Nature; Wall Street Journal

 

ANSWERS: 1) human; 2) mated; 3) DNA; 4) sapiens; 5) jawbone; 6) Neanderthal; 7) interbreeding; 8) Africa; 9) genome; 10) Middle

 

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