Europeans carry more than 500 genetic 'fragments' inherited from archaic human species such as Neanderthals — including some linked to prostate cancer, iron retention, blood clotting speed and height
- Researchers compared modern European and African genomes with each other
- This enabled them to identify genetic fragments that came from archaic humans
- Species like Neanderthals interbred with our ancestors over 50,000 years ago
- Almost half of the Neanderthal genome exists in the European gene pool today
The average European carries more than 500 genetic 'fragments' from Neanderthals and other archaic human species, a study has found.
Among this heritage is included genes that are linked to prostate cancer risk, iron retention, blood clotting speed and smaller height.
The ancestors of Europeans are known to have mated with Neanderthals and other archaic humans more than 50,000 years ago — trading genetic material.
As a result, outside of Africa, around 2 per cent of people's genomes come from interbreeding with other ancient human species.
Researchers used a new approach in the study, eschewing the usual method of hunting for known archaic human genes in the genomes of modern populations.
Instead, they isolated archaic fragments from modern genomes by eliminating the material known to have not come from interbreeding with other archaic humans.
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The average European carries more than 500 genetic 'fragments' from Neanderthals and other archaic human species, a study has found
Pictured, a phylogenetic tree showing the complex evolutionary history of hominins and when human species branched off from the Great Apes
The study was conducted by researchers from the genetics firm deCODE, in collaboration with experts from universities in Denmark, Germany and Iceland.
The team's data support previous conclusions that — outside of Africa — around 2 per cent of people's genomes are derived from ancient human species, thanks to the interbreeding of Homo sapiens and Neanderthals some 50,000 years ago.
However, the researchers also found more evidence of fragments derived from the Denisovans — another archaic human species that interbred with both the Neanderthals and Homo sapiens — than identified previously.
Past studies have been limited by relying on the three archaic individuals — one Denisovan and two Neanderthals — whose genes have been adequately sequenced.
Experts have scoured modern genomes looking for fragments that match up with those found in the preserved DNA from these three individuals alone.
In their study, however, deCODE CEO Kari Stefansson and colleagues instead compared the whole genomes of 28,000 Icelanders — a number nearly 10 per cent of their entire population — with those of 286 sub-Saharan Africans.
This enabled them to use the African genomes as a baseline, as they knew that they would not contain any genes transferred over from Neanderthals, Denisovans or other archaic human species as a result of interbreeding.
Any genetic fragment in the Icelandic genomes that also appeared in the African genomes therefore could not have come from archaic humans, and could thus be eliminated from the analysis.
This left the team with some 15 million fragments that might have come from archaic human species, which — once repeated and overlapping fragments were removed — was boiled down to 50,000 distinct archaic fragments.
These account for some 38–48 per cent of the readable genome, although the team also noted that some areas of the human genome — totalling around a quarter of it, and including the whole X chromosome — harbour no archaic fragments.
In their study, however, deCODE CEO Kari Stefansson and colleagues instead compared the whole genomes of 28,000 Icelanders — a number nearly 10 per cent of their entire population — with those of 286 sub-Saharan Africans. This enabled them to use the African genomes as a sort of baseline, as they knew that they would not contain any genes transferred over from Neanderthals, Denisovans or other archaic human species as a result of interbreeding
Finally, with the archaic fragments isolated from within the European genome, the researchers were able to examine those that appeared to function without being driven by an association with their modern counterparts.
They found five — among which was one that had previously been linked to decreased levels of prostate specific antigen and risk of prostate cancer, but was not known to be archaic in origin.
The other fragments serve to decrease the levels and mass of haemoglobin, increase the time it takes for blood to clot and decrease one's height.
'Whether individually or collectively, our genome enables us to learn more about who we are by telling us where we come from,' Dr Stefansson said.
'This paper is a kind of ancestry report for one branch of our species,' he added.
'It's telling us that in this particular neighbourhood we are not just Homo sapiens but also the descendants of ancient archaic humans – cousin species whose lineage is thus not entirely extinct'
'We are scratching the surface of what this hybrid legacy means.'
'What we know is that in the 50,000 years from their time to this, our adaptability and diversity have enabled us to mix and move, settle and thrive in every corner of the planet as they did not.'
'In these dark days we would do well to remember that our differences are literally the mark of our success, and so to help each other as best we can.'
The full findings of the study were published in the journal Nature.
A CLOSE HUMAN RELATIVE, THE NEANDERTHALS, DIED OUT AROUND 50,000 YEARS AGO
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.
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