Scientists Find Earliest Sign of Cultivated Crops in Americas

Scientists exploring the western slopes of the Andes in northern Peru have found seeds of domesticated squash from almost 10,000 years ago, about twice the age of previously discovered cultivated crops in the region.

The find in Peru and recent research in Mexico, anthropologists say, are evidence that farming developed in parts of the Americas nearly as early as it did in the Middle East, which has been considered the birthplace of the earliest agriculture.

Digging under house floors and grinding stones and in stone-lined storage bins, the archaeologist Tom D. Dillehey of Vanderbilt University, in Nashville, uncovered the squash seeds at several places in the Ñanchoc Valley, near the Pacific coast about 400 miles north of Lima. The excavations also yielded peanut hulls and cotton fibers — about 8,500 and 6,000 years old, respectively.

The new, more precise dating of the plant remains, some of which were collected two decades ago, are reported by Dr. Dillehey and colleagues in Friday’s issue of the journal Science.

Their research also turned up traces of other domesticated plants, including a grain, manioc and some unidentified fruits, and stone hoes, furrowed garden plots and small-scale irrigation canals from approximately the same period.

The researchers concluded that these beginnings in plant domestication “served as catalysts for rapid social changes that eventually contributed to the development of intensified agriculture, institutionalized political power and towns in both the Andean highlands and on the coast between 5,000 and 4,000 years ago.”

The evidence at Ñanchoc, Dr. Dillehey’s team wrote, indicated that “agriculture played a more important and earlier role in the development of Andean civilization than previously understood.”

In an accompanying article on early agriculture, Eve Emshwiller, an ethnobotanist at the University of Wisconsin, Madison, was quoted as saying the reports of early dates for plant domestication in the New World were remarkable because the activity appeared to have occurred not long after humans first colonized the Americas, which is now thought to be at least 13,000 years ago.

The article also noted that 10,000-year-old cultivated squash seeds have recently been reported in Mexico, along with evidence of domesticated maize there by 9,000 years ago. Scholars now think that plants were domesticated independently in at least 10 “centers of origin;” those centers, in addition to the Middle East, Mexico and Peru, include places in Africa, southern India, China and New Guinea.

In the Fertile Crescent of the Middle East, an arc from modern-day Israel through Syria and southeastern Turkey to Iraq, wheat and barley were domesticated at least 10,000 years ago, and rye may have been domesticated 13,000 years ago. Experts in ancient agriculture suspect that the transition from foraging to cultivation started much earlier than that, and was not as abrupt a transformation as the archaeological record would seem to indicate.

Dr. Dillehey has devoted several decades to research on ancient cultures in South America. His most notable previous achievement was the discovery of a campsite of hunger-gatherers at Monte Verde, in Chile, which dates to about 13,000 years ago. Most archaeologists recognize this as the earliest well-documented human occupation site uncovered so far in the New World.

Other explorations in recent years have yielded increasing evidence of settlements and organized political societies that flourished in the coastal valleys of northern Peru, possibly as early as 5,000 years ago. Until now, the record of earlier farming in the region had been sparse.

Initial radiocarbon dating of the plant remains from Ñanchoc was based on wood charcoal buried at the sites, but the results varied widely and were considered unreliable. More recent radiocarbon dating, with a technique called accelerator mass spectrometry, relied on measurements from undisturbed buried charcoal and an analysis of the actual plant remains.

The distribution of building structures, canals and furrowed fields, Dr. Dillehey said, indicated that the Andean culture was moving beyond cultivation limited to individual households toward an organized agricultural society.

Botanists studying the squash, peanut and cotton remains determined that the specific strains did not grow naturally in the Ñanchoc area. The peanut, in particular, was thought to be better suited to cultivation in tropical forests and savannas elsewhere in South America. The wild ancestor of squash has yet to be identified, though lowlands in Colombia are thought to be a likely source.

So if the new research shows that the “horticultural economies in parts of the Andes took root by about 10,000 years ago,” Dr. Dillehey’s team said, it remains to be seen when and where the domestication of squash, peanuts and cotton took place.