Tibetans' Genetic Edge Didn't Come From Homo Sapiens

Tibetans are largely unique among humans for their ability to live comfortably at high altitudes. The Tibetan Plateau, nicknamed the "roof of the world," stands an average of 15,000 feet above sea level. That's just shy of 3 miles—making it the highest plateau on the planet and an area whose air contains roughly 40% less oxygen. But Tibetans don't seem to have adapted over the millennia, nor is a genetic mutation responsible for their ability: Researchers have discovered they share a gene with our hominid cousin the Denisovans, who went extinct some 40,000 years ago; their study was published in Nature yesterday.

Known as EPAS1, the gene allows Tibetans to absorb scarce oxygen without creating extra red blood cells—something the rest of us mortals must deal with at altitude, and which can lead to dangerously high blood pressure, cardiac arrest, and lower birth-weight babies, reports NPR. Since many Europeans and Asians are 1% to 3% Neanderthal, we know our species intermingled with other closely related but distinct species, but we've only known about Denisovans since 2010, when scientists sequenced the DNA from two teeth and a pinkie found in a cave in Siberia, reports Slate. The study's lead author tells Time the findings prompt an even larger question: "We found the Denisovan species at the DNA level, but how many other species are out there that we haven’t sequenced?” (Click to read about where scientists think Denisovans lived.)