The gene attributed to Tibetans’ ability to live at extremely high altitudes originally came from an ancient hominin, according to a study published online Wednesday in the journal Nature.
Conducted by UC Berkeley researchers and scientists abroad, the study compared the genes of 40 Han Chinese with 40 Tibetans and showed that the high-altitude gene was expressed almost exclusively by members of the Tibetan group, despite the two groups’ close genetic similarities. The specific gene, the study found, was very unusual compared to those of other humans but did match DNA sequenced from an extinct hominin called a Denisovan — implying that an ancestor of modern Tibetans had interbred with them.
“We were trying to understand the genetic variation of that gene,” said Emilia Huerta-Sanchez, an assistant professor at UC Merced’s School of Natural Sciences and an author of the study. “And it turns out that it looks like the Tibetans were very different from other populations at that gene.”
According to the study and a previous report published by some of the same researchers in the journal Science, the Tibetan gene prompts an optimal level of hemoglobin production for high altitudes, thereby preventing blood from becoming too viscous while still promoting sufficient oxygenation. Now that researchers have isolated the gene, Huerta-Sanchez said, individuals may someday be able to see whether or not they are genetically adapted to thrive at high elevations, such as the Tibetan Plateau, which has an average elevation of more than 14,000 feet above sea level.
The transfer of genetic material from archaic to modern humans — called adaptive introgression — may have had a larger role in human evolution than biologists once thought, she said.
“It’s only been recently that we’ve found genetic evidence of this mating between modern humans and archaic humans,” Huerta-Sanchez said. “But I think this is one of the most clear examples that the genetic exchange was useful because it allows a modern human population to live in a very challenging environment.”
The new findings may also have medical applications for people with conditions caused by poor blood oxygen levels, she said, though the biological mechanism by which the gene functions and the significance of adaptive introgression overall are still unclear.
“There’s a lot of questions that are not answered yet,” Huerta-Sanchez said.
A previous version of this article quoted Emilia Huerta-Sanchez as saying “But I think this is one of the most clear examples that the genetic exchange was mutual because it allows a modern human population to live in a very challenging environment.” In fact, Huerta-Sanchez used the word “useful” not “mutual.”