It is now established fact that when humans migrated out of Africa, they found a land populated with many other species of ancient human who had made the journey before them. When our ancestors interacted, it is clear that some mating went on, as we carry evidence of these encounters in our DNA.
Some studies have suggested that the ancient hominid genes we retain actually do us harm, but a new study to be published in Molecular Biology and Evolution has found that for the Inuit populations of Greenland, they may actually be beneficial. The team found that two genes related to cold adaption may have their origins in an enigmatic ancient hominid known as the Denisovans.
“The Inuit DNA sequence in this region matches very well with the Denisovan genome, and it is highly differentiated from other present-day human sequences,” explains Fernando Racimo, who led the study. “Though we can't discard the possibility that the variant was introduced from another archaic group whose genomes we haven't sampled yet.”
It is already well established that all people who are descended from the few hundred that migrated out of Africa have a small portion of Neanderthal DNA in them, after our ancestors met with the ancient humans and interbred. Interestingly, we don’t all share the same sections, meaning that up to around 60 percent of the entire Neanderthal genome exists within the modern human population.
When scientists look at the DNA from people from Southeast Asia, though, another picture arises. Not only do they have the remnants of our ancestors' interactions with Neanderthals preserved in their genome, but that of another interaction with another ancient human species. Known as the Denisovans, the only physical evidence of these ancient peoples are a few finger bones and teeth discovered in a cave in Siberia, but their DNA lives on in this corner of the world.
Because all indigenous Americans, including Inuit Greenlanders, are derived from people migrating from east Asia around 11,000 years ago, it also means that they too have portions of Denisovan DNA in them. But like with the Neanderthals, they don’t share the same bits. It now seems that those living in the colder northern climates may have retained the genes from this ancient species as an aid in their survival in the frozen landscape.
The genes in question are central to cold adaptation by generating heat from one type of body fat, and was previously identified to be central to the Inuit’s survival in the frigid environment. The evidence suggests that these genes may have originated in the Denisovans, and due to their beneficial nature, survived in those still living in the northern latitudes to this day.