Early agriculture flowered in Mexico.

Beginning around 6,000 years ago, a swampy stretch of Mexico's Gulf Coast served as a hotbed of plant domestication in the Americas, according to a new study. New World agriculture probably originated there and in other parts of what is now Mexico, conclude archaeologist Kevin O. Pope of Geo Eco Arc Research in Aquasco, Md., and his coworkers.

Their Gulf Coast discoveries, published in the May 18 SCIENCE, follow another team's report that residents of Mexico's southern highlands domesticated squash and maize between 10,000 and 7,000 years ago (SN: 2/17/01, p. 103).

Pope's group focused on the Gulf Coast site of San Andres, which people occupied from about 7,000 until 2,000 years ago. The researchers calculated radiocarbon dates for charcoal and wood from different soil layers at the site.

Pollen grains typical of domesticated maize appeared at San Andres about 6,000 years ago, the researchers say. Moreover, a pollen grain at the site that may have come from domesticated manioc--a starchy, edible plant--dates to 5,800 years ago.

Excavations at San Andres also yielded the earliest evidence yet of sunflower domestication in the New World. A domesticated sunflower seed and a partially preserved sunflower unearthed at the site date to about 4,000 years ago.

Therefore, contrary to one current theory, eastern North American groups didn't independently domesticate sunflowers a millennium later, Pope's team contends. Researchers haven't found wild precursors of modern sunflowers in eastern North America, the team notes. Also, molecular evidence suggests that sunflowers in the Americas derived from a single genetic source. Mexico harbored that founding population, in Pope's view.

"The evidence [points to] Mexico as a hearth for [plant] domestication in the New World," says Mary E.D. Pohl of Florida State University in Tallahassee, a coauthor of the new study.

Despite the work at San Andres, scientific knowledge of ancient agricultural practices in Mexico "is largely a blank blackboard," remarks archaeologist Bruce D. Smith of the Smithsonian Institution in Washington, D.C.

Smith remains unconvinced that domesticated sunflowers and other lines of New World crops sprang from only a few cultivation centers in Mexico or anywhere else.