Traces of a chemical found in cacao—the main ingredient in chocolate—were found in several drinking vessels from various sites in Pueblo Bonito, a complex of sandstone "great houses" in Chaco Canyon, New Mexico.

Ancestral Puebloan peoples built the complex, the epicenter of the ancient Chaco culture, in stages between A.D. 850 and 1150.

(See "16 Indian Innovations: From Popcorn to Parkas.")

But cacao, a tropical fruit that grows in Central and South America, was cultivated in prehistoric times only in Mesoamerica, a region that stretches from Mexico to Costa Rica (see map).

The findings suggest the New Mexico complex also served as a trading hub for Mesoamericans and Puebloans between the 11th