Andean Populations Show Genetic Adaptation to Potato-Rich Diet

Indigenous communities in the Andes domesticated the potato between 6,000 and 10,000 years ago, making the starch-rich tuber a central part of their diet. This long-term reliance on potatoes as a reliable food source at high altitudes led to genetic adaptations that remain observable in Peruvian descendants who speak the Quechua language.

A study published this week in the journal Nature Communications found that these individuals possess an average of 10 copies of the AMY1 gene. That is two to four more copies than most people have, and the highest number recorded globally. The timing of the genetic changes coincided with the advent of potato domestication.

The AMY1 gene governs production of the enzyme amylase in saliva, which breaks down starch in the mouth when eating starchy foods. Individuals with more copies of the gene may produce more of the enzyme, facilitating better metabolism of high-starch diets.

Researchers said the greater dosage may also influence the body's microbiome. "It is a wonderful case of culture shaping biology," said one of the study's senior authors. The research analyzed genomic data from more than 3,700 people across 85 populations in the Americas, Europe, Africa and Asia, including 81 native Quechua speakers of Andean ancestry in Peru.

Over time, evolutionary forces favored extra copies of the AMY1 gene in ancient Andean populations. A genetic variant must provide some advantage to become widespread in a population. "Therefore, one hypothesis is that people with more copies of AMY1 may have been better able to process starch-rich foods, including potatoes," said a doctoral student and co-lead author of the study.

Individuals with higher copy numbers may have had an advantage, left more descendants over generations, and increased the frequency of the variant in Andean populations today. Potatoes represented one of the main sources of calories in the ancient Andean diet and were at the heart of the Inca food supply.

The crop thrived at the high altitudes where these communities lived.

Lactose tolerance is another example of diet-driven evolutionary adaptation, involving a gene related to an enzyme that breaks down lactose in milk. The potato adaptation in the Andes adds to understanding of how dietary changes have shaped human biology.

The study's senior authors noted that the findings highlight the importance of dietary adaptation in human evolutionary history. They said the research has implications for metabolism, health and the impact of domestication events on human biology. Potatoes were brought to Europe and the rest of the world following the Spanish conquest of the Inca Empire in the 16th century.

At 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. "In Peru, there are about 3,000 to 4,000 different kinds of potato, but the majority of the world has access to only a select few strains," said a doctoral student and co-lead author of the study.