People who both travel to and live at high altitudes typically cope with lower oxygen levels by increasing red blood cell production, which can help get more oxygenated blood to organs and tissues. But the increase in red blood cells also makes blood thicker, stickier, and more difficult to pump, putting a strain on the cardiovascular system and leading to health issues, including heart failure and high blood pressure.
Some populations that live at high altitudes, such as Tibetan highlanders, have evolved to limit increases in red blood cell numbers. In contrast, Andeans that live at high altitudes overproduce red blood cells, yet manage to avoid the negative consequences. In a study published today (November 2) in The American Journal of Human Genetics, researchers report the first clues as to how they skirt the risks of extra red blood cells: variants in sequences related to genes that regulate cardiovascular function and heart development.
The authors “look at a specific population that has a unique evolutionary history,” says Tatum Simonson, who did not participate in the work but studies the physiology and genetics of high-altitude adaptation at the University of California, San Diego. “Because of that history, we can learn a lot about the genes that are involved in some of these responses to low oxygen and the phenotypes that are associated with them.”
The researchers studied a group of Andean highlanders who speak a language called Aymara and live at elevations topping 3,600 meters. “We can’t experiment genetically with humans, but nature has sometimes [done] experiments for us,” says coauthor Rasmus Nielsen of the University of California, Berkeley. By examining what happens when humans live with different environmental stressors, “we can learn something about the interactions between our genetics and the environment.”