A publication of the Archaeological Institute of America
Dating of squash seeds from a cave in Oaxaca, Mexico, has confirmed that plant domestication in the Americas began some 10,000 years ago. The new finding, reported by Smithsonian archaeologist Bruce Smith in the journal Science, indicates that planting began in the New World about the same time as in the Near East and China.
Originally excavated in 1966 by University of Michigan archaeologist Kent Flannery, then at the Smithsonian, the Guilá Naquitz (White Cliff) Cave revealed evidence of human occupation dating back 10,000 years; finds included squash seeds, rind fragments, and peduncles, or stems. Some of the larger seeds were identified as belonging to a domesticated squash species, Cucurbita pepo, which includes modern pumpkins. Based on radiocarbon dates of charcoal found with the seeds, and on the size and thickness of the rinds, Flannery estimated the squash were nearly 10,000 years old. This date drew fire from some archaeologists who believed the seeds came from later occupation layers and did not offer clear signs of domestication. These scholars have held that the transition from hunting and gathering to agriculture occurred between 5,000 and 3,500 years ago.
Flannery could not, however, date the specimens directly because radiocarbon-dating techniques then available would have required destroying the samples. Smith used accelerator mass spectrometer radiocarbon dating, which can be used on very small samples, to establish the seeds' age. "Bruce has vindicated us," says Flannery. "He's shown that our excavations didn't have any mixing of occupation layers."
So far there is no evidence to suggest that New World people were cultivating anything but squash before 5,000 years ago. While Chinese and Near Eastern peoples appear to have shifted to a diversified agricultural economy within 1,000 years of the cultivation of their first crops, in the Americas the transition to an agricultural life-style appears to have taken much longer. Though Smith hesitates to predict when evidence for other early New World crops will emerge, he does admit that it "would seem unusual to have 5,000 years pass before corn and beans become domesticated."