Corn: The Long And Winding Road To Domestication Includes Many Surprises

Scientists have long believed that farmers in southern Mexico first domesticated corn, otherwise known as maize, from teosinte, an ancient forbearer some 9,000 years ago before it made its way around the world. But a recent study shows that this much-beloved plant took some complicated twists and turns along the way.

From their journeys to South America via southern Mexico, humans brought the forerunners of today’s modern corn more than 6,500 years ago, Science News reports. And those plants contained a wellspring of genes from teosinte, corn’s wild ancestor. That’s according to Logan Kistler, an archeologist and evolutionary ecologist with the Smithsonian in Washington, D.C. and his colleagues. It turns out that farmers in Mexico and parts of the Amazon (in what is now present-day Brazil and Bolivia) continued to modify the partially domesticated plant over a period stretching several thousand years.

Teosinte is the ancestor of modern corn. Image license CC SA 2.0 by foam via Wikimedia Commons

Farmers in the southwestern region of the Amazon were also growing cassava and rice. When maize arrived they began growing that as well. They likely used local techniques to domesticate it even further, including growing the plant in soil enriched with charcoal, compost, and other ingredients, Kistler said.

Previously, it was believed that the domestication process began in Mexico’s Balsas River Valley, near Mexico City, and was later introduced elsewhere in the Americas, Reuters reports.

But the researchers’ findings show that an additional, and crucial phase of domestication occurred simultaneously in the Amazon and Mexico.

“We’ve shown that parts of the process were taking place thousands of kilometers [from Mexico] and thousands of years after the whole thing started,” Kistler said in a press conference Tuesday.

There was another twist in corn’s story 4,000 years ago as the plant was introduced more widely in South American lowlands. And this is about the very same time that the increasingly domesticated plant reached what is now the U.S. Southwest.

Then another big wave of maize cultivation in the Americas as it spread eastward, moving from the foothills of the Andes almost all the way to the Atlantic coast about 1,000 years ago, the researchers found. Seeds of partly domesticated maize were planted in fields where they mixed with wild teosinte. Over time, fully domesticated species of maize emerged in numerous cultivation areas.

But when the Europeans invaded the Americas about 500 years ago, corn turned into a global crop. And it was accompanied by other crops that originated in the New World, including avocados, sweet potatoes, chocolate, tomatoes, and peanuts.

Perhaps most amazingly, this study shows that pathways to domestication varied for a number of plants and animals notes paleoethnobotanist, Robert Spengler of the Max Planck Institute For The Science of Human History in Jena, Germany.

“Maize is an amazing example of how plants that evolved to accommodate human seed dispersal and cultivation gained a strong evolutionary advantage,” noted Spengler, who was not involved in the study.

Corn’s beginnings were humble but varied. Isn’t it fascinating that something that regularly winds up on the world’s dinner table obviously has a long story to tell?

The researchers published their findings in the journal Science.

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