Potato-based diet changed the genetics of Andean people

Indigenous peoples in the Andes domesticated potatoes—an excellent source of starch, vitamins, minerals, and fiber—between 6.000 and 10.000 years ago, making the crop a central part of their diet. These peoples then underwent genetic adaptations beneficial to such a diet, which are still seen in their descendants in Peru today.

New genomic research documents how these descendants - speakers of the Quechua language of the once great Inca Empire - experienced a boost that included the AMY1 gene, linked to starch digestion, a function beneficial to people whose diets are largely based on potatoes, Reuters reports.

The study found that these people have an average of 10 copies of the AMY1 gene - two to four more than most people. No other known population in the world has a higher number. The study also showed that the onset of these genetic changes in this population coincided with the beginning of potato domestication.

"It's a wonderful example of how culture shapes biology," said evolutionary and anthropological geneticist Omer Gokcumen of the University at Buffalo, one of the lead authors of the research published this week in the journal Nature Communications.

"This highlights the importance of dietary adaptation in human evolutionary history, with implications for metabolism, health, and the impact of domestication on human biology," said anthropological geneticist Abigail Bigham of the University of California, Los Angeles (UCLA), also one of the study's lead authors.

At the molecular level, AMY1 controls an enzyme called amylase, which is present in saliva and is responsible for breaking down starch in the mouth when a person eats starchy foods. A person with more copies of this gene can produce more of this enzyme.

Researchers say that this higher amount may facilitate better metabolism of starchy foods. Amylase may also be involved in regulating the microbiome - the natural community of microbes in the body - which can change with dietary changes.

Lactose tolerance is another example of a diet-driven evolutionary adaptation, and it involves a gene linked to the enzyme that breaks down lactose in milk.

In the new study, researchers analyzed genomic data from more than 3.700 people from 85 populations in the Americas, Europe, Africa and Asia, including 81 native speakers of Quechua of Andean origin in Peru.

The researchers say that over time, evolutionary forces appear to have favored extra copies of the AMY1 gene in ancient Andean inhabitants.

To become widespread, a genetic variant may provide a certain advantage.

"Therefore, one hypothesis is that people with more copies of the AMY1 gene may have been better able to process starchy foods, including potatoes," said University at Buffalo doctoral student and study co-author Luane Landau.

"Individuals who were born with more copies of the AMY1 gene may have had an advantage over those who did not and left more offspring over generations. Over time, this could explain why the genetic version associated with a high number of AMY1 copies is more common in Andean populations today," Landau said.

Potatoes represented a reliable source of food - a crop that thrived at the high altitudes where these people lived.

"It was one of the main sources of calories in the ancient Andean diet," said University at Buffalo doctoral student and study co-author Kendra Shear.

The potato was at the heart of the Inca Empire's food supply. It was brought to Europe and the rest of the world after the Spanish conquest of the Inca Empire in the 16th century.

"Its global culinary spread is testament to its widespread acceptance," Bigam said.

In markets in the Andean highlands and elsewhere in Peru, Quechua speakers sell a wide variety of potatoes, with flesh of various colors, including purple, blue, red, gold, white and even black, Reuters reports.

"In Peru, there are about 3.000 to 4.000 different types of potatoes, but most of the world only has access to a small number of varieties. So there's a whole world of different types of fries that are possible," said Shir.