For thousands of years, potatoes have been a staple of life in the Andes. Indigenous Andean communities were the first to domesticate the starch-rich crop, transforming it into a dietary foundation long before potatoes spread across the globe. New research suggests that this deep reliance on potatoes may have influenced human evolution by shaping genes involved in starch digestion.
Indigenous people in Peru today carry more copies of the starch-digestion gene AMY1 than any other known population. A study co-led by researchers at UCLA and the University at Buffalo indicates that natural selection began favoring Indigenous Andeans with higher numbers of AMY1 copies around the time potatoes became established in the Andean highlands, approximately 6,000 to 10,000 years ago.
The findings were recently published in the journal Nature Communications.
How the AMY1 Gene Helps Digest Starch
People with more copies of AMY1 typically produce higher levels of the salivary amylase enzyme. This enzyme helps break down starch in the mouth and may allow people to process starchy foods more efficiently, according to Abigail Bigham, an associate professor of anthropology at UCLA who studies populations in the Peruvian Andes and the Himalayas of Nepal.
For the study, Bigham and her team of evolutionary anthropologists collected DNA from Peruvian Andean Quechua speakers. They compared these samples with genomic databases containing thousands of DNA samples from dozens of modern human populations.
“The high-altitude Andes are known for being a rich region for understanding human evolutionary adaptation — for instance, hypoxia, in which tissues do not get enough oxygen,” said Bigham, whose previous work with co-author Kelsey Jorgensen, then a postdoctoral scholar with Bigham, provided evidence of selection in the starch digestion pathway of Andean peoples. “This new research highlights how the Andes are useful for understanding human evolutionary adaptation to other selective environmental pressures like diet.”
Co-corresponding author Omer Gokcumen, a professor of biological sciences at the University at Buffalo, previously showed that the first duplication of AMY1 occurred in humans at least 800,000 years ago. He said the new study offers unusually strong evidence that natural selection acted on the gene in the Andes after potato cultivation began.
“Biologists have long suspected that different groups of humans have evolved genetic adaptations in response to their diets,” he said, “but there are very few cases where the evidence is this strong.”
How Potato Cultivation Influenced Andean Evolution
The ancestors of Indigenous Andeans already carried varying numbers of AMY1 copies before settling in the highlands and domesticating potatoes. Some individuals had relatively few copies, while others carried many more.
As potatoes became a major food source, people with higher AMY1 copy numbers appear to have gained an evolutionary advantage because of their potential ability to digest starch more efficiently.
The researchers estimated that beginning approximately 10,000 years ago, people with about 10 or more AMY1 copies had a 1.24% survival or reproductive advantage per generation.
“Evolution is chiseling a sculpture, not constructing a building,” Gokcumen said. “It’s not as if Indigenous Andeans gained additional AMY1 copies once they started eating potatoes. Instead, those with lower copy numbers were eliminated from the population over time, perhaps because they had fewer offspring, and the ones with the higher copy numbers remained.”
Over many generations, this process produced a notable genetic difference. Indigenous people living in Peru today carry an average of 10 AMY1 copies, approximately two to four more copies than any of the other 83 populations examined in the study.
Genetic Evidence Linking Potatoes to Human Adaptation
The researchers also compared Indigenous Peruvians with the Maya, an Indigenous population in Mexico that shares some evolutionary history with Andean peoples but does not have a longstanding tradition of potato farming.
On average, Indigenous Peruvians carried 10 copies of AMY1, compared with six copies among the Maya.
This difference supported the possibility that potato cultivation played an important role. However, the researchers also needed to rule out another major event in Indigenous American history.
After European contact in the 15th century, Indigenous populations throughout the Americas declined dramatically because of disease, famine, violence, conflict and the rapid loss of genetic diversity.
The team therefore investigated whether this severe population bottleneck could have reduced the number of people carrying fewer AMY1 copies. If so, the pattern might have appeared to result from natural selection even if potato consumption was not the cause.
Distinguishing between the effects of potato farming and the later population collapse was one of the study’s central challenges.
Using advanced ultra-long DNA sequencing technologies and newly available comparative datasets, the researchers found that high AMY1 copy numbers had already become more common in the Andes several thousand years before Europeans arrived.
This timing supports the conclusion that diet-related natural selection, rather than the later population decline, was responsible for the genetic pattern observed in Indigenous Peruvians today.
What Ancient Potato Farming Reveals About Human Evolution
Bigham said the findings could inspire additional research into human populations living at high elevations, where people face challenges beyond low oxygen levels. Andean communities have also historically dealt with limited food resources, extreme cold and intense ultraviolet radiation.
The research raises a broader question about how human populations may continue adapting to modern diets. People today have greater access to foods and cuisines from around the world than ever before, but genetic adaptation remains an important part of the human story.
“There are ideas out there like the paleo diet, which is adapted to the Paleolithic environment and says we’re not suited to eat foods that come post-domestication,” she said. “But I think this research shows that human populations have responded and evolved to changing food conditions within the last 10,000 years. Our metabolic pathways are not simply a product of that Paleolithic past.”
Other collaborators on the research included researchers from the University of Kansas, Pennsylvania State University, the University of Pennsylvania, the University of Puerto Rico at Cayey, Syracuse University, Cayetano Heredia University in Peru and Bilkent University in Turkey.
The work was supported by the National Science Foundation, National Institutes of Health and the Leakey Foundation.
Source: www.sciencedaily.com