We’re all a little more Neanderthal than we thought: Study claims ancient Europeans introduced Neanderthal DNA to African populations 30,000 years ago
- Study found the first conclusive evidence for Neanderthal DNA in Africans
- Neanderthal DNA previously only found in Americans, Europeans and Asians
- Neanderthals and humans hybridised after Homo sapiens migrated out of Africa
- Ancient Europeans descended from these events then migrated back into Africa
- Mating between these European migrants and native Africans passed trace amounts of Neanderthal DNA into their genes
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.
Scroll down for video
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)
TIMELINE OF HOW NEANDERTHAL DNA REACHED AFRICA
100,000 years ago – A large wave of migration out of Africa occurred
50,000 years ago – Parts of this Homo sapiens population mated with Neanderthals
DNA from Neanderthals was then passed down the generations, becoming steadily more diluted
30,000 years ago – European and East Asian populations split
Some Europeans then migrated back into Africa where they mated with native Africans
Neanderthal DNA was then passed into future generations of Africans from the European lineage
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.
WHAT DO WE KNOW ABOUT HUMANKIND’S JOURNEY OUT OF AFRICA?
The traditional view
The traditional ‘Out of Africa’ model suggests that modern humans evolved in Africa and then left in a single wave around 60,000 years ago.
The model often holds once modern humans left the continent, a brief period of interbreeding with Neanderthals occurred.
This explains why individuals of European and Asian heritage today still have ancient human DNA.
There are many theories as to what drove the downfall of the Neanderthals.
Experts have suggested that early humans may have carried tropical diseases with them from Africa that wiped out their ape-like cousins.
Others claim that plummeting temperatures due to climate change wiped out the Neanderthals.
The predominant theory is that early humans killed off the Neanderthal through competition for food and habitat.
How the story is changing in light of new research
Recent findings suggest that the ‘Out of Africa’ theory does not tell the full story of our ancestors.
Instead, multiple, smaller movements of humans out of Africa beginning 120,000 years ago were then followed by a major migration 60,000 years ago.
Most of our DNA is made up of this latter group, but the earlier migrations, also known as ‘dispersals’, are still evident.
This explains recent studies of early human remains which have been found in the far reaches of Asia dating back further than 60,000 years.
For example, H. sapiens remains have been found at multiple sites in southern and central China that have been dated to between 70,000 and 120,000 years ago.
Other recent finds show that modern humans reached Southeast Asia and Australia prior to 60,000 years ago.
Based on these studies, humans could not have come in a single wave from Africa around this time, studies have found.
Instead, the origin of man suggests that modern humans developed in multiple regions around the world.
The theory claims that groups of a pre-human ancestors made their way out of Africa and spread across parts of Europe and the Middle East.
From here the species developed into modern humans in several places at once.
The argument is by a new analysis of a 260,000-year-old skull found in Dali County in China’s Shaanxi Province.
The skull suggests that early humans migrated to Asia, where they evolved modern human traits and then moved back to Africa.
Source: Read Full Article