What do you think of this fact?
On the Tibetan plateau, the air is so thin that lots of visitors from the lowlands run out of steam fast. The people who have lived there for generations handle it remarkably well. And part of their secret comes from relatives who no longer exist.
Life in thin air
The Tibetan plateau sits at around 4,000 meters. The air there has about 40 percent less oxygen than at sea level. Lowlanders’ bodies respond by cranking out lots of red blood cells. That makes the blood thicker, which comes with its own problems.
In many Tibetans, things work differently. Their bodies raise hemoglobin and red blood cell levels only slightly at high altitude, avoiding those side effects. A big part of that is down to a particular version of a gene called EPAS1.
A hand-me-down from the Denisovans
That version shows up in about 87 percent of Tibetans but only about 9 percent of Han Chinese. A team led by geneticist Rasmus Nielsen at the University of California, Berkeley, took a closer look. They sequenced that stretch of DNA in 40 Tibetans and 40 Han Chinese.
The surprise, published in Nature in 2014: the gene variant almost certainly came from the Denisovans, an extinct group of ancient humans. Apparently, ancestors of modern humans mixed with Denisovans at some point and picked up the gene. In Tibet, natural selection then made it spread widely.
Nielsen called it the first time a gene from another kind of human had been clearly shown to help modern humans adapt to their environment. He also admitted the team originally thought the idea was pretty far-fetched.
Hardly any Denisovan bones are known: Denisova Cave in Siberia’s Altai Mountains has yielded just a finger bone, a toe bone and two teeth. Most of their story comes from their DNA.
Ancient help
Denisovans were only discovered in 2008. The fact that they still help people live on the roof of the world sounds almost like science fiction. But it shows how much of our prehistory is still written in our genes.
Some heirlooms don’t come in a jewelry box. They come in your DNA.