Dolores Piperno of the Smithsonian Tropical Research Institute in Panama and the National Museum of Natural History, and archeology Professor Tom Dillehay of Vanderbilt University, said their finding sets the date of the earliest human consumption of beans and fruit from cultivated pacay trees back by more than 2,000 years and indicates Western Hemisphere people were committed farmers earlier than previously thought.

The preserved teeth were found in northern Peru's Nanchoc Valley and carbon dating showed human bone, plant remains and charcoal closely associated with the teeth were approximately 6,000 to 8,000 years old.

"Some teeth were dirtier than others. We found starch grains on most of the teeth," Piperno said. "We found starch from a variety of cultivated plants: squash, Phaseolus beans -- either limas or common beans, possibly, but not certainly the former, pacay and peanuts."

She said starch from squash found on the teeth show early people were eating the plants and not simply using them for non-food purposes, such as for making containers or net floats.

The research appears in the early online edition of the Proceedings of the National Academy of Sciences.