The recent study claims that corn's wild ancestor, maize, brought to South America 6,500 years ago, was a partially farmed version.
The study, published in Dec. 14 Science journal, challenges a time-honored belief that southern Mexican farmers shaped teosinte long before the crop spread to other parts of Americas.
However, the new findings derived from reconstructing maize's genetic past reveals that a second phase of domestication was already underway in southwestern Amazon — what is Brazil and Bolivia today — even while the domestication in Mexico continued.
The Birth Of Corn
By discovering the evidence regarding corn's early domestication in southwestern Amazon, the researchers managed to solve a puzzle.
"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," said Logan Kistler, archaeologist and evolutionary ecologist from Smithsonian Institution in Washington DC in a Dec. 11 news conference.
The ancestors of modern corn were brought to South America from Mexico over 6,500 years ago, explains Kistler. The farmers in southwestern Amazon and Mexico continued to tame a partially domesticated plant for thousands of years, as those plants still contained genes known as teosinte from its wild ancestors.
Researchers also suspect that the famers back then would have integrated this maize into their existing repository of crops and used regular techniques, such as growing in soil enriched with compost and other ingredients, in their further domestication of the plant.
"Maize is an amazing example of how plants that evolved to accommodate human seed dispersal and cultivation gained a strong evolutionary advantage," says paleoethnobotanist Robert Spengler of the Max Planck Institute for the Science of Human History in Jena, Germany, who was not a part of this new study.
"Maize is one of the most widespread cultivated plants in the world, dominating crops grown in most of the U.S. Midwest, Central America and parts of South America," he says.
The Step Forward
Yoshi Maezumi, a tropical paleoecologist at the University of the West Indies in Jamaica, who worked with Kistler on the maize study, says that they hope to use their study findings to gain a better understanding of how tropical crops were domesticated and what it reveals about the environmental conditions and the civilizations that cultivated them.
"What we've shown is that the process of domestication is more complicated than previously thought," Maezumi says. "New (archaeological) sites are being discovered all the time. There's so much new information coming out that's changing the way we think about what humans were doing on the landscape and how they were using the land."
Kistler's way forward is to start working backward and find clues from ancient DNA to get a clear picture of what the earliest forerunners of maize looked like.
