She found the match on her first try.
The chili pepper starch grains found in domestic strains, the researchers note, are distinct from any other plant starches as well as from wild-pepper starches.
The ancient pepper grains were almost always found with corn and often associated with yams, potatoes, squash, beans, and fruits. This suggests that they belong to systems of "sophisticated agriculture and complex cuisine," Perry said.
In some sites this advanced cultivation and palate predated pottery, which contradicts the popular theory that pottery and sophisticated agriculture spread together, the researchers note.
The earliest chili pepper starch grains were found at two sites in southwestern Ecuador that are dated to about 6,100 years ago.
Perry and her colleagues point out that Ecuador is not considered a center of domestication for any of the five cultivated chili pepper species, suggesting they were brought to the region via migration or trade.
"The initial domestication must have occurred earlier than this," Perry said.
Scientists believe chili peppers, which gain their distinct zest from the powerful irritant chemical capsaicin, arose in what is now Bolivia. (Related: "Tarantula Venom, Chili Peppers Have Same 'Bite,' Study Finds [November 8, 2006].)
But they were first cultivated and domesticated in Mexico, the southern Andes, and the Amazon lowlands, according to the theory (South America map).
"What's going to be interesting, I think, is to go back to older sites and see if we can document the transition from wild to domesticated chilies using these microfossils," Perry said.
Sandra Knapp is a botanist at the Natural History Museum in London. In a Science commentary, she writes that the new findings indicate more ancient cultivation and more widespread use of peppers than previously believed.
"It also opens up new avenues of research into how the peoples of the Americas transported and traded plants of cultural importance."
(Editor's note: Perry has received funding from the National Geographic Society for unrelated research. National Geographic News is part of the National Geographic Society.)
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