The indigenous peoples of the Andes Mountains domesticated the potato – an excellent source of starch, vitamins, minerals and fiber – 6,000 to 10,000 years ago, making the tuber a central part of their diet. These populations later developed beneficial genetic adaptations for such a diet, adaptations that are still found today in their descendants in Peru, reports Reuters.
New genetic research documents how these descendants – speakers of the Quechua language from the once great Inca Empire – went through a process of genetic reinforcement involving a gene called AMY1, responsible for starch digestion, a useful function for people on a potato-based diet.
The study found that these populations have an average of 10 copies of the AMY1 gene – two to four more than most people. No other known population worldwide exceeds this number. The research also showed that the appearance of these genetic changes in that population coincided with the beginnings of potato domestication.
“It's a wonderful case of culture shaping biology,” said University at Buffalo geneticist Omer Gokcumen, one of the lead authors of the research published this week in the journal Nature Communications.
The researchers point out that the discovery is not a mere curiosity
“This highlights the importance of dietary adaptation in human evolutionary history, with implications for metabolism, health, and the impact of domestication events on human biology,” explained UCLA geneticist Abigail Bigham, also one of the lead authors of the study.
At the molecular level, AMY1 controls an enzyme called amylase, present in saliva and responsible for breaking down starch in the mouth when a person eats starchy foods. A person who has more copies of the gene can produce a larger amount of this enzyme.
Researchers say this higher dose may facilitate more efficient metabolism of starchy diets. Amylase may also have a role in regulating the microbiome – the body's natural collection of microbes – which can change with dietary changes.
Lactose tolerance is another example of diet-driven evolutionary adaptation, involving a gene associated with an enzyme that breaks down lactose in milk.
The researchers compared the descendants of the Incas with populations around the world
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 Quechua speakers of Andean ancestry in Peru.
The researchers said it seems likely that, over time, evolutionary forces have favored the appearance of extra copies of AMY1 in ancient Andean populations.
For a genetic variant to become widespread, it must provide some advantage.
“Therefore, one hypothesis is that people with more copies of AMY1 may have been able to process starchy foods, including potatoes, more efficiently,” said Luane Landau, a doctoral student at the University at Buffalo and co-senior author of the study.
“Individuals who were born with a higher number of copies of AMY1 may have had an advantage compared to those who did not have this trait and left more offspring over the generations. Over time, this could explain why the genetic variant associated with a higher number of copies of AMY1 has become more common in Andean populations today,” said Landau.
Potatoes were brought to Europe after the conquest of the Inca Empire
Potatoes were a reliable food source – a vegetable crop that thrived at the high altitudes where these populations lived.
“They were one of the main sources of calories in the diet of ancient Andean populations,” explained Kendra Scheer, a doctoral student at the University at Buffalo and co-senior author of the study.
Potatoes were central to the food supply of the Inca Empire. They were brought to Europe and the rest of the world after the Spanish conquest of the Inca Empire in the 16th century.
“Their global culinary spread is a testament to their universal popularity,” Bigham said.
In markets in the Andean highlands and elsewhere in the state of Peru, Quechua speakers sell a wide variety of potatoes, with cores in various colors, including purple, blue, red, gold, white, and even black.
“There are about 3,000 to 4,000 different types of potato in Peru, but most people in the world only have access to a few select varieties. So there's a whole world of different types of fries that would be possible,” Scheer said.
