Ancient Andean DNA shows maize was eaten centuries before population turnover

A quiet change in diet

Did ancient farming spread because new groups moved in, or did local people adopt new foods first? To answer this, scientists gathered ancient Andean DNA from 212 people. These remains span 7,000 years in the high plateau of Colombia, known as the Altiplano Cundiboyacense.

For five thousand years, an autochthonous lineage—people native to the land—lived in small, isolated groups. Their DNA changed slowly over generations through genetic drift. This term refers to random changes in genes over time. They lived without external gene flow, meaning there was no genetic mixing with outside neighbours.

Eating maize before the turnover

Around 2,800 years BP (years Before Present, where present is fixed at 1950), things changed. These descendants of local hunter-gatherers shifted their diet. Scientists tracked this by checking isotopic signatures. These are chemical traces inside ancient bones that show what foods a person ate.

The tests showed clear signs of maize consumption. Yet the DNA of these people had not changed. They still carried the same local genetic roots. This shows that the change in food was decoupled from population replacement. The dietary shift happened without an influx of outside people.

The major genetic break occurred centuries later, around 2,000 BP, alongside the Herrera culture. Outside groups arrived and largely replaced the original native line. These new groups carried admixed ancestry, which means genetic mixture from two earlier populations. They descended from Chibchan and Amazonian-Andean groups who had mixed around 4,000 BP. Later, their descendants split into regional groups that matched local cultural borders.

What scientists still want to learn

This method matters because it tests bones and genes together. It reveals whether cultural habits spread by trade or by mass movement. However, the study has limits. The early evidence of maize consumption rests on just two individuals from around 2,800 BP. Also, the findings only cover one high Andean plateau. Scientists still do not know what prompted local groups to take up maize, nor which paths migrants took into the highlands.