November 11th, 2016 by James Ayre
The so-called Neanderthals and Denisovans were two, of very likely a great many, of the branches or relatives (depending on your view) of humans that lived in Asia, Europe, and the Near East, for up to a million years.
(If you include other homo erectus descendants, that have lived in Asia and probably Europe, relatives as well then this figure can be stretched to nearly 2 million years. Some of the genetics of these peoples are likely still around in the world today, and the Neanderthals and Denisovans seem to have themselves picked up some genetics from unknown hominids living the regions in question before or with them.)
Notably, Neanderthal genetics in Europe, the Near East, the Caucasus, and other parts of Asia, seem to slowly being subsumed on the population level as various mass migration waves through these regions have continued over the last 10,000 or so years. (The Germanic mass migrations into Europe ~2,000 years ago, the Celt one from the Middle East during the late Bronze Age collapse, the Italic one before, the Iberian one before that, etc.) The recently sequenced genome of a fellow living in Central Europe 8,000 or so years ago, for instance, shows much, much higher Neanderthal ancestry than any modern humans do.
These inherited genetics from Neanderthals and Denisovans though, what are they? Have they benefitted the humans that possess them? Was the spread of Homo sapiens throughout Asia, Europe, the Americas, and Oceania, reliant upon these genetics (obtained through interbreeding)?
New research suggests something along those lines, with the identification of “126 different places in the genome where genes inherited from those archaic humans remain at unusually high frequency in the genomes of modern humans around the world.”
Interestingly, amongst many other things, these regions relate to genetic traits associated with immune system functioning and skin quality.
“Our work shows that hybridization was not just some curious side note to human history, but had important consequences and contributed to our ancestors’ ability to adapt to different environments as they dispersed throughout the world,” commented Joshua Akey of University of Washington School of Medicine in Seattle.
Here’s more: “Akey says it’s relatively straightforward today to identify sequences that were inherited from ‘archaic’ ancestors. Studies show that non-African individuals inherited about 2% (Author’s note: This figure is at least as high as 5% in some people.) of their genomes from Neanderthals. People of Melanesian ancestry inherited another 2% to 4% of their genomes from Denisovan ancestors. But it hasn’t been clear what influence those DNA sequences have had on our biology, traits, and evolutionary history.”
Continuing: “In the new study, the researchers took advantage of recently constructed genome-scale maps of Neanderthal and Denisovan sequences identified in more than 1,500 geographically diverse people. Their sample included close to 500 individuals each from East Asia, Europe, (Neanderthals + Denisovans) and South Asia (Denisovans). They also analyzed the genomes of 27 individuals from Island Melanesia, an area including Indonesia, New Guinea, Fiji, and Vanuatu. The researchers were searching for archaic DNA sequences in those human genomes at frequencies much higher than would be expected if those genes weren’t doing people any good. While the vast majority of surviving Neanderthal and Denisovan sequences are found at relatively low frequencies (typically less than 5%), the new analyses turned up 126 places in our genomes where these archaic sequences exist at much higher frequencies, reaching up to about 65%. 7 of those regions were found in parts of the genome known to play a role in characteristics of our skin. Another 31 are involved in immunity.”
In other words, these Neanderthal- and Denisovan-derived sequences were very likely to be particularly advantageous inheritances in the environments that they operated.
Notably, while 31 of the 125 sequences identified by the researchers related to immune system functioning, and 7 to skin, there were clearly quite a lot of other ones that related to other factors.
As alluded to above, Neanderthals and Denisovans themselves seem to have picked up around 8% of their genome from other hominids that were met by them at some point.
As there are quite a lot of inaccurate representations (projections is more accurate) of Neanderthals and Denisovans circulating in pop culture, I’ll direct those interested to this article “Neanderthals and Denisovans — Who Were They? Comparison Of Evidence Against Pop Culture Projection” if they want to get a more accurate, and far more interesting image of who these highly successful and persistent peoples actually were.
The new research is detailed in a paper published in the Cell Press journal Current Biology.
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