Human evolution is at work in the Andes mountains. The Quechua, an Indigenous people in Peru who have lived at altitudes above 2500 meters for at least the past 11,000 years, have evolved genetic adaptations to survive their harsh environment. A new study finds these extreme conditions can change chemical modifications that control the activity of that DNA. These “epigenetic” alterations are the first evidence that growing up in the mountains can alter not just genes, but how the body uses them.
Scientists have long wondered whether environmental stress, like low oxygen concentrations, can shape gene activity in highland people, says anthropologist Cynthia Beall of Case Western Reserve University who studies high altitude adaptations in Tibet. This “pioneering” research shows it is not only possible, says Beall, who was not involved with the study, but likely that epigenetic changes are involved.
Your environment can cause chemical modifications to your DNA that turn genes on or off, or lower or raise the activity of certain genes. The strategy allows people to adapt to their surroundings much more rapidly than pure genetics allows. Still, it’s unclear what role epigenetics plays in helping people adapt to a life at high altitude.
So in the new study, a team of international researchers from Peru, Germany, and the United States looked at an epigenetic process called methylation, in which cells add chemical tags called methyl groups to DNA. The team studied three groups: Quechua who were born and raised above 3000 meters, Quechua who were born at high altitudes but moved to sea level when they were young, and Quechua whose families moved to sea level before they were born.
The data revealed significant differences in the methylation patterns among the groups, the team reported last month in Genome Biology and Evolution. Genes involved with creating red blood cells and building endurance muscle were more methylated in Quechua who were born and spent most of their early life at high altitudes, regardless of whether they moved to lower altitudes later in life. These epigenetic modifications were probably cemented into the DNA of Quechua because they were exposed to low oxygen conditions before birth and during childhood.
But other methylated regions, including around one gene involved in the breakdown of sugar, were exclusive to the group born and raised at high elevation, the team found. This suggests such changes only arise when Quechua are constantly exposed to high altitude.
The scientists were not able to ascertain whether any of the epigenetic modifications they saw changed the activity of the genes. But they did find that many of the changes were irreversible, meaning the methylation of DNA in Quechua who moved to lower altitudes as adults continued to act as though they were at high altitude.
“I think it’s exciting that we found anything at all,” says lead author Ainash Childebayeva, a postdoctoral researcher at the Max Planck Institute for the Science of Human History. The findings, she says, lend more evidence to the idea that humans can evolve to challenging conditions much more rapidly than previously thought.
Childebayeva hopes her work will inspire others to investigate these questions in highland people around the world. One scientist, at least, is considering it. The study, Beall says, “makes me want to talk with the person who does my DNA analyses and see if we should look at methylation.”