Indigenous Andeans in Peru carry an average of 10 salivary amylase gene copies—the highest found in the study—versus about seven globally, a pattern linked to stronger starch and potato digestion.
Genome data from 3,723 people across 85 populations suggest natural selection began favoring higher copy numbers around 10,000 years ago, after potato domestication in the Andes.
Researchers estimated Andean individuals with 10 or more copies had a 1.24% higher chance of surviving and reproducing than those with fewer copies, a small-seeming advantage that compounds across generations.
The study also found high amylase copy numbers in Akimel O'odham samples, hinting that other Indigenous American groups may have reached similar adaptations through different diets.
Scientists still do not know the exact functional payoff of extra copies, but are testing links to calorie extraction, metabolism, the microbiome and immune function.