If you’re uncomfortable with that seldomly-disputed scientific assertion, maybe you should take a seat before reading about the latest conclusion that researchers from Temple University in Philadelphia have reached.
In their new study, out in the latest issue of the scientific journal Nature, Joshua Schraiber and Fernando Villanea say that the intermingling of the species was not limited to one event, as previously believed. They say humans and their neanderthal cousins dipped their spoon in the primordial evolutionary stew by swapping genes for millennia — in a sex romp that lasted for more than than 30,000 years.
They used a huge dataset of modern human genomes to compare the patterns of Neanderthal DNA in people of East Asian and European descent, since the original moment of inter-species hanky-panky was thought to have happened between Neanderthals and prehistoric humans in the Middle East more than 50,000 years ago.
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“To our surprise the best-fitting model actually included multiple matings in both East Asia and Europe,” Schraiber told McClatchy.
Cue the “bow chicka wow-wow” music.
The study’s authors found that “the proportion of Neanderthal ancestry is ~12-20 higher in East Asian individuals relative to European individuals,” and ran the numbers using maximum likelihood models and machine learning. It told them that a single co-mingling into the gene pool just wasn’t feasible for the amount of Neanderthal DNA that still courses through us as a species.
And it would seem to make sense. If you kept bumping into someone for 30,000 years, that’s enough time for the sparks to fly more than once — and that’s precisely what humans and Neanderthals did, the authors argue.
Today, Neanderthal DNA accounts for about two percent of the average person’s genetic makeup, according to Science Alert — an echo, Schraiber and Villanea say, back to all the times one of your Neanderthal ancestors climbed on top of one of your human ones.
But all the intermingling wasn’t just between humans and Neanderthals. Enter the lesser-known evolutionary sister-wife species, the Denisovans. The authors say their work is “consistent with recent work showing that humans interbred with Denisovans multiple times.”
Denisovans, or Homo sapiens [subspecies] denisova, have been argued to be distinct from both Homo sapiens and Neanderthals, and traces of their existence have been found in Siberia, according to Discover.
“It’s just inherently interesting that anatomically modern humans and Neanderthals interbred,” Schraiber said, according to Popular Science. “I wonder what would happen if there were Neanderthals today?”