Scientists have found, for the first time, conclusive evidence that Neanderthal DNA exists in modern-day Africans.
A new study by Princeton University reveals that African people — who were previously thought to have no Neanderthal DNA — got around 0.3 per cent of their genes from our ancient ancestors.
African people obtained a sliver of Neanderthal DNA after breeding with humans, who migrated to Africa from Europe around 30,000 years ago.
Ancestors of these Europeans are known to have bred with Neanderthals around 20,000 years earlier, providing an indirect pathway for Neanderthal DNA into Africans.
The new shows that native Europeans, Asians, Africans and Americans all have some Neanderthal DNA – and non-Africans have even more than previously assumed.
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Study finds previous assumptions that Africans did not breed with Neanderthals directly are true, but they inadvertently received Neanderthal DNA from those who originated in parts of the world whose ancestors had mated with Neanderthals (pictured, the two stages which led to Neanderthal DNA being found in Africans)
Neanderthals disappeared around 40,000 years ago but their DNA lives on in modern humans thanks to interbreeding between the two species (file photo)
Dr Aaron Wolf, study author from the University of Washington, told MailOnline: ‘We believe a large portion of the Neanderthal ancestry in African populations is due to historic back-migration from an ancestral European population into Africa.’
Around 100,000 years ago, a large wave of migration out of Africa occurred, from which the vast majority of modern non-African populations are descended.
Parts of this population interbred with Neanderthals – around 50,000 years ago – and passed Neanderthal DNA onto today’s human populations.
‘We believe some of this Neanderthal carrying non-African population returned to Africa, and introduced Neanderthal DNA into African populations,’ said Dr Wolf.
‘Importantly, we believe this happened after the split of the European and East Asian populations (~30,000 years ago).’
Scientists identified regions of Neanderthal ancestry in Africans for the first time by identifying, on average, 17 megabases (Mb) of Neanderthal DNA per individual.
This corresponds to approximately 0.3 per cent of the African peoples’ genome stemming from the Neanderthals, who went extinct around 40,000 years ago.
This is significantly less than the levels of Neanderthal ancestry in Europeans (51 Mb/individual), East Asians (55 Mb/individual), and South Asians (55 Mb/individual).
East Asians, who were thought to have 20 per cent more Neanderthal DNA than Europeans, actually only have 8 per cent more, the scientists discovered.
‘This suggests that most of the Neanderthal ancestry that individuals have today can be traced back to a common hybridisation event involving the population ancestral to all non-Africans, occurring shortly after the Out-of-Africa dispersal,’ Dr Joshua Akey of Princeton University and study author says.
The study confirms previous assumptions that Africans did not breed with Neanderthals directly.
However, it shows that they inadvertently received Neanderthal DNA from those who originated in parts of the world whose ancestors had mated with Neanderthals.
‘I am struck by the fact that we often conceptualise human history in very simple terms,’ Dr Akey says.
‘For example, we often imagine there was a single dispersal out of Africa that happened 60,000 to 80,000 years ago that led to the peopling of the world.
‘However, our results show this history was much more interesting and there were many waves of dispersal out of Africa, some of which led to admixture between modern humans and Neanderthals that we see in the genomes of all living individuals today.’
WHO WERE THE NEANDERTHALS?
The Neanderthals were a close human ancestor that mysteriously died out around 50,000 years ago.
The species lived in Africa with early humans for hundreds of millennia before moving across to Europe around 500,000 years ago.
They were later joined by humans taking the same journey some time in the past 100,000 years.
The Neanderthals were a cousin species of humans but not a direct ancestor – the two species split from a common ancestor – that perished around 50,000 years ago. Pictured is a Neanderthal museum exhibit
These were the original ‘cavemen’, historically thought to be dim-witted and brutish compared to modern humans.
In recent years though, and especially over the last decade, it has become increasingly apparent we’ve been selling Neanderthals short.
A growing body of evidence points to a more sophisticated and multi-talented kind of ‘caveman’ than anyone thought possible.
It now seems likely that Neanderthals buried their dead with the concept of an afterlife in mind.
Additionally, their diets and behaviour were surprisingly flexible.
They used body art such as pigments and beads, and they were the very first artists, with Neanderthal cave art (and symbolism) in Spain apparently predating the earliest modern human art by some 20,000 years.
African people — who were previously thought to have no Neanderthal DNA — got 0.3 per cent of their genes from our ancient ancestors. This breakthrough means scientists have now discovered native Europeans, Asians, Africans and Americans all have some Neanderthal DNA
In a study published in the journal Cell, Princeton University researchers used a computational method, called IBDmix, to assess the DNA of 2,504 modern Africans and non-Africans.
The method looks for sections of DNA in two individuals that is identical which implies they 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 then used the principle of IBD — identity by descent — to identify Neanderthal DNA in the human genome.
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.
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.
