Neanderthals live on in some of us – DNA study

WASHINGTON (Reuters) – Neanderthals and modern  humans interbred, probably when early humans first began to  migrate out of Africa, according to a genetic study released on  Thursday.

People of European, Asian and Australasian origin all have Neanderthal DNA, but not Africans, researchers reported in Friday’s issue of the journal Science.

The study may help resolve the long-running debate over  whether Neanderthals and modern humans did more than simply  live side by side in Europe and the Middle East.

“Those of us who live outside Africa carry a little  Neanderthal DNA in us,” said Svante Paabo of the Max Planck  Institute in Munich, Germany, who led the study.

“The proportion of Neanderthal-inherited genetic material  is about 1 to 4 per cent. It is a small but very real proportion  of ancestry in non-Africans today,” Dr David Reich of Harvard Medical School in Boston, who worked on the study, told  reporters in a telephone briefing.

While the findings may lead to jokes about cave-man  behaviour or looks, Paabo said his team cannot identify any  Neanderthal “traits.” “As far as we can tell these are just  random pieces of DNA,” he said.

The researchers used modern methods called whole genome  sequencing to examine the DNA from Neanderthal bones found in  Croatia, Russia, Germany and Spain, including some crushed leg  bones from one Croatian cave that some scientists believe are  evidence of cannibalism.

The researchers developed new methods to gather, distinguish and sequence the Neanderthal DNA. “In those bones  that are 30,000, 40,000 years old there is of course very  little DNA preserved,” Paabo said. He said 97 per cent or more  of the DNA extracted was from bacteria and fungi.
They compared the Neanderthal sequences to DNA sequences from five people from Europe, Asia, Papua New Guinea and  Africa.

Understanding evolution
“Their analysis shows the power of comparative genomics and  brings new insights to our understanding of human evolution,” Dr Eric Green, director of the National Human Genome Research Institute at the National Institutes of Health, said in a  statement.

The results add to a picture of modern humans living  alongside with and interacting on the most intimate levels with  similar humans who have now gone extinct.

“It certainly is an indication of what went on socially when Neanderthals and modern humans met,” Paabo said.
“There was interbreeding at some little level. I would  prefer to leave it to others who want to quarrel over whether  to call us separate species or not,” he added. “They were not  genetically very distinct from us.”

The DNA sequences date back to somewhere around 80,000  years ago, when modern humans moving through the Middle East on  their way out of Africa would have encountered the southernmost populations of Neanderthals.  The researchers identified five genes unique to  Neanderthals, including three skin genes. “This suggests that  something in the physiology or morphology of the skin has  changed in humans,” Paabo said.

In March Paabo and colleagues reported they had found a  previously unknown human species that lived 30,000 years ago  alongside modern humans and Neanderthals in Siberia.

Scientists have for years speculated that several different  species of humans lived side by side at various times over the  past million years. But many would have lived in tropical zones  where bones are not easily preserved.

Paabo said modern-day Africans may carry some of that  unknown DNA even if they do not have Neanderthal ancestors.

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