Extinct human cousin gave Tibetans advantage at high elevation

An unusual variant of a gene involved in regulating the body’s production of hemoglobin — the molecule that carries oxygen in the blood — became widespread in Tibetans after they moved onto the high-altitude plateau several thousand years ago. This variant allowed them to survive despite low oxygen levels at elevations of 15,000 feet or more, whereas most people develop thick blood at high altitudes, leading to cardiovascular problems.

“We have very clear evidence that this version of the gene came from Denisovans,” a mysterious human relative that went extinct 40,000-50,000 years ago, around the same time as the more well-known Neanderthals, under pressure from modern humans, said principal author Rasmus Nielsen, UC Berkeley professor of integrative biology. “This shows very clearly and directly that humans evolved and adapted to new environments by getting their genes from another species.”

From I recall reading, Denisovans aren’t thought to have been that different from Neanderthals, so this probably isn’t as profound as it initially sounds.  Still, it’s a fairly significant discovery.

For decades, there was a debate between two camps in paleo-anthropology, the out-of-Africa camp, and the multi-regional camp.  The out-of-Africa people believed that modern humans evolved in Africa and subsequently migrated around the world.  The multi-regional camp believed that modern humans in each region evolved from archaic humans in that region, with lots of gene flow between the regions keeping us one species.

The weight of scientific evidence is now firmly on the out-of-Africa side, with genetic studies now allowing scientists to track prehistoric human migrations.  But like many things in science, it’s not a complete victory, since it looks like humans in each region did receive a small amount of gene flow from local archaic humans, and this contribution appears to have provided benefits, such as in the case of Tibetans, a gene for tolerating high altitude conditions.