Second Wild Grass Identified as Maize Ancestor

DAVIS, CALIFORNIA—Previous research has shown that maize was first domesticated some 9,000 years ago by hunter-gatherers in lowland Mexico’s Balsas River Basin from a teosinte subspecies called parviglumis. Maize then spread along the Pacific coastline to Panama by about 7,800 years ago, and Peru by about 6,700 years ago. Now, a new genetic study conducted by evolutionary biologist Jeffrey Ross-Ibarra of the University of California, Davis, and his colleagues has identified a second wild grass as an ancestor of today’s maize, according to a Science Magazine report. When the researchers examined maize genomes from traditional varieties, modern varieties, and ancient plants from the southwestern United States, Mexico, and parts of South America, they found evidence for the ancestry of a highland teosinte subspecies called mexicana in all of the samples, except for one 5,500-year-old cob from the southeastern coast of Peru. Early farmers in central Mexico probably mixed mexicana with domesticated maize between 6,000 and 4,000 years ago, Ross-Ibarra explained. The new variety, which likely had slightly bigger cobs, more kernels per row, and could withstand more sunlight, then spread quickly. Farmers may have found that the genetic variation provided by mexicana made the maize crop more reliable, Ross-Ibarra surmised. For more on Indigenous maize cultivation, go to “Maize Maintenance.”