Ancient people of the Americas first domesticated plants 10,000 to 12,000 years ago in lowland Ecuador, new research suggests. The findings overturn the longstanding dogma that New World farming was born in highland Mexico, calling into question an old theory of the origins of agriculture.
The classic story of agriculture comes from the Middle East, where wheat, barley, pigs, and sheep were quickly domesticated and then spread to other parts of the world. Many archaeologists tried to tell a similar story for the Americas, and they found supporting evidence for the domestication of squash, and later corn, in the highlands of Mexico. Squash remains found there were the oldest known (ScienceNOW, 8 May 1997, but a new study suggests that was merely because the dry climate favors the preservation of large plant remains.
The researchers used silicate particles called phytoliths--microscopic remains of decaying plant cells--which survive in humid climates. For squash, phytolith size reflects the size of a plant's fruit, and therefore whether it was wild or a domesticated variety bred for size.
Archaeologist Dolores Piperno of the Smithsonian Tropical Research Institute in Balboa, Panama, and colleague Karen Stothert of the University of Texas, San Antonio, examined an existing excavation of the Las Vegas culture, which occupied southwestern Ecuador beginning about 14,000 years ago. The lowest layers contained small phytoliths, ranging from 65 micrometers to 72 micrometers, but starting 10,000 to 12,000 years ago, the phytoliths were longer than 80 micrometers, a clear signature of domesticated plants, they report in the 14 February issue of Science.
Piperno says that the study contradicts the old notion that crops have "centers of origin." This may be true in the Middle East, she says, but the Americas are radically different. "There is no single zone where you had a complex of crops emerging that spread widely over the continent," she says. Anthropologist Mary Pohl of Florida State University in Tallahassee agrees, adding that phytolith studies such as Piperno's open the door to understanding how those cultures worked, she says.