Peruvians are great at digesting starch. That's because potatoes granted them a boon

A new study reveals that Indigenous Peruvian Andeans carry the world's highest number of copies of the starch-digesting amylase gene, AMY1, shaped by thousands of years of potato farming. Scientists have confirmed this is the result of natural selection, not chance.

In Short

• Peruvian Andeans carry ten copies of the starch-digesting AMY1 gene.
• Potato farming began shaping Andean DNA nearly 10,000 years ago.
• Maya people, same ancestry, fewer copies, and no potato-farming history.

Somewhere in the high-altitude valleys of the Andes, thousands of years ago, something quietly extraordinary happened inside the human body. A gene began multiplying. And it did so because of a potato.

A new study published in Nature Communications, co-led by researchers from University of California, Los Angeles (UCLA) and the University at Buffalo, has found that Indigenous Peruvian Andeans carry the highest known copy numbers of the salivary amylase gene, called AMY1, of any population on Earth.

AMY1 is the gene that produces amylase, an enzyme in your saliva that begins breaking down starch the moment food enters your mouth.

More copies of this gene means more enzymes, and more enzymes means more efficient starch digestion.

The average person carries around seven copies of AMY1. Peruvian Andeans carry ten.

WHY DO PERUVIANS HAVE MORE COPIES OF THIS GENE?

The answer, researchers believe, lies in the potato. The Andes is the birthplace of potato cultivation, dating back roughly 6,000 to 10,000 years ago.

For millennia, Andean communities have survived on diets where potatoes account for about 54 per cent of daily food intake. That is an extraordinary dependence on a single starch-rich crop.

The study analysed DNA from 3,723 individuals across 85 global populations.

It found that those Andeans who happened to carry more AMY1 copies had a 1.24 per cent survival or reproductive advantage per generation once potato farming took hold.

Over thousands of years, individuals with fewer copies of the gene gradually disappeared from the population. Those with more copies thrived.

This is evolution at work, chiselling quietly across generations.

HOW DO SCIENTISTS KNOW THIS WAS NATURAL SELECTION AND NOT JUST CHANCE?

The researchers used several sophisticated statistical tests and ruled out the possibility that this was simply a random fluke.

They also ruled out the dramatic population collapse that followed the European arrival in the Americas in the 15th century as a cause.

The genetic data clearly showed that high AMY1 copy numbers were already rising thousands of years before Europeans arrived.

Interestingly, the Maya of Mexico, who share ancestry with Andeans but do not have a history of potato farming, carry only six copies on average.

The study is a reminder that what your ancestors ate is written, in very real terms, inside your DNA.

- Ends