Written by Freda Kreier
Human evolution is at work in the Andes Mountains. Quechua, an indigenous people of Peru who have lived at altitudes above 2,500 meters for at least the past 11,000 years, has developed genetic adaptations to survive its harsh environment. A new study reveals that these extreme conditions can change the chemical modifications that control the activity of that DNA. These “epigenetic” changes are the first evidence that growing up in the mountains can change not only genes, but also how the body uses them.
Scientists have long wondered whether environmental stress, such as low oxygen concentrations, can shape genetic activity in people in the hills, says anthropologist Cynthia Beall of Western Western Reserve University, who studies adaptations to high altitudes in Tibet. This “pioneering” research shows that this is not only possible, says Bell, who was not involved in the study, but it is also likely that these are epigenetic changes.
Your environment can cause chemical modifications to your DNA that turn genes on or off, or reduce or increase the activity of certain genes. The strategy allows people to adapt to the environment much faster than pure genetics allows. However, it is not clear what role epigenetics plays in helping people adapt to life at high altitudes.
Thus, in a new study, a team of international researchers from Peru, Germany and the United States studied an epigenetic process called methylation, in which DNA cells add chemical labels called methyl groups. The team studied three groups: Quechua who were born and raised above 3,000 meters, Quechua who were born at high altitudes but moved to sea level as young people, and Quechua whose families moved to sea level before they were born .
The data revealed significant differences in methylation patterns between groups, the team reported last month Biology and evolution of the genome. The genes involved in red blood cell production and endurance muscle building were more methylated in Quechua who were born and spent most of their early lives at high altitudes, whether or not they later moved to lower altitudes. These epigenetic modifications were probably cemented into Quechua DNA because they were exposed to low oxygen conditions before birth and during childhood.
But other methylated regions, including about one gene involved in sugar breakdown, were exclusive to the group born and raised on a high elevation, the team found. This suggests that such changes occur only when Quechua are constantly exposed to high altitudes.
The scientists could not determine if any of the epigenetic modifications they saw altered gene activity. But they found that many of the changes were irreversible, meaning DNA methylation in Quechua that had moved to lower altitudes while adults continued to act as if they were at high altitudes.
“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, provide more evidence for the idea that humans can evolve into challenging conditions much faster than previously thought.
Childebay hopes her work will inspire others to explore these issues with people in the mountains around the world. At least one scientist is considering it. The study, Beall says, “makes me want to talk to the person doing my DNA analysis and see if we should look at methylation.”