Genetic analysis traces the roots of corn

Scientists conducting a genetic and archaeological analysis of corn and its use by humans have discovered the history is far more complicated than previously thought.

The process of turning wild corn into a crucial food source began 9,000 years ago in Mexico and an earlier partly cultivated version was taken to South America 6,500 years ago.

Further development of the plant proceeded at the same time in both places, the researchers said last week.

Until now, it was thought that the domestication process had occurred in south-central Mexico’s Balsas River Valley, south of Mexico City, and that corn was only later introduced by people elsewhere in the Americas.

The new findings revealed a second phase occurred in the south-western Amazon region spanning parts of Brazil and Bolivia.

Corn became a global crop after Europeans reached the Americas 500 years ago. Other crops originating in the Americas include potatoes, sweet potatoes, tomatoes, peanuts and avocados.

“After the beginning stages of domestication, people are already moving this new crop over huge distances, even before the evolutionary process of domestication has fixed all the traits favoured by humans,” said Logan Kistler, of the Smithsonian Institution’s National Museum of Natural History in Washington.

Corn’s wild predecessor is a grass called teosinte, with negligible cobs and kernels in a tough casing.

“Maize is one of the most important plant species for humans,” said Mr Kistler, the lead author of the study published in the journal Science.