Maize was domesticated from its wild grass ancestor more than 8,700 years ago, according to biological evidence uncovered by researchers in Mexico’s Central Balsas River Valley.

This is the earliest dated evidence — by 1,200 years — for the presence and use of domesticated maize.

The researchers, led by Anthony Ranere of Temple University and Dolores Piperno of the Smithsonian National Museum of Natural History, report their findings in the March 24 edition of Proceedings of the National Academy of Sciences (PNAS).