Ever heard of an ancient group of humans called the Denisovans? It’s not entirely surprising, considering that that the only way we’ve been able to study this ancient group of people is through genetic sequencing of modern humans.
At some point in the history of the human species, our ancestors mated with this group and had children who carried both human and Denisovan DNA, a discovery made after Denisovan traces were found in modern human DNA.
This piqued the interest of geneticists all over the world, prompting a major study to be conducted on 257 different genomes of present-day people from 120 non-African populations (because African ancestors never left Homo sapien’s place of origin, they do not have any Denisovan ties).
Their findings confirmed that people from Papua New Guinea, Australia, and other Oceania areas seem to have the strongest link to the Denisovan species, with their genomes consisting of anywhere from 3% to 6% Denisovan. Which is significant when comparing to the 2% of Neandertal that makes up all non-African genomes.
Population geneticists Sriram Sankararaman (University of California) and David Reich (Harvard University) estimated that modern humans mated with Neandertals around 50,000 years ago and with Denisovans about 40,000 years ago.
Rasmus Nielsen, a geneticist at UC Berkeley who was not involved with the study, says that this find “suggests a scenario of extensive, and almost free, matings” between modern humans and practically any other similar species we came across.
The results of this free love between modern humans and similar species are both positive and negative.
One of the positives can be seen in Himalayan populations that have gained a Denisovan gene that reduces levels of hemoglobin in the blood, allowing them to live comfortably at incredibly high altitudes.
So, why don’t see crazy Denisovan Homo Sapien hybrid people today? Because, as it is often seen in other interspecies hybrids, one ancestry, or set of genes, does not get inherited by the X chromosome, meaning the hybrid male offspring are born sterile or infertile.
“That’s the barrier that keeps the species from mixing,” says Sankararaman.
Thus, any traces of Denisovan ancestry seen in modern humans today would have been passed down by female hybrids, or, our ancient grandmothers.
(h/t* Science Mag*)