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Africans and Europeans 'have more Neanderthal ancestry than previously thought'

By Nina Massey, PA Science Correspondent

All modern humans, including Africans, carry some Neanderthal ancestry in their DNA, research suggests.

After sequencing the Neanderthal genome scientists discovered all present day non-African individuals carry some of the ancestry in their DNA.

But researchers say that for the first time they have found evidence of its presence in African populations too.

When the first Neanderthal genome was sequenced, using data collected from ancient bones, it was accompanied by the discovery that modern humans in Asia, Europe and America inherited approximately 2% of their DNA from Neanderthals.

This proved that humans and Neanderthals had interbred after humans left Africa.

Since then new methods have continued to catalogue Neanderthal ancestry in non-African populations.

In a study published in the journal Cell, Princeton University researchers say their computational method, called IBDmix, enabled them to search both populations for the ancestry.

The method draws its name from the genetic principle identity by descent (IBD), in which a section of DNA in two individuals is identical because those individuals once shared a common ancestor.

Co-first author Lu Chen, a postdoctoral research associate at Princeton's Lewis-Sigler Institute for Integrative Genomics (LSI), said: "This is the first time we can detect the actual signal of Neanderthal ancestry in Africans.

"And it surprisingly showed a higher level than we previously thought."

Scientists used the principle of IBD to identify Neanderthal DNA in the human genome.

They did this by distinguishing sequences that look similar to Neanderthals because we once shared a common ancestor around 500,000 years ago, from those that look similar because of interbreeding in the more recent past, 50,000 years ago.

The new method uses characteristics of the Neanderthal sequence itself to distinguish shared ancestry from recent interbreeding.

Researchers were able to identify Neanderthal ancestry in Africans for the first time and estimate that Europeans and Asians to have more equal levels of Neanderthal ancestry than previously thought.

The study also suggests migrations from ancient Europeans back into Africa introduced Neanderthal ancestry into African populations.

It adds that some of the detected Neanderthal ancestry in Africans was actually due to human DNA introduced into the Neanderthal genome.

While researchers acknowledged the limited number of African populations they analysed, they hope their new method and their findings will encourage more study of Neanderthal ancestry across Africa and other populations.

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