Who says food fads can't last?

Thousands of years before the advent of Tex-Mex, ancient Americans were spicing up stew with red hot chili peppers.

New fossil evidence shows prehistoric people from southern Peru up to the Bahamas were cultivating varieties of chilies millennia before Columbus' arrival brought the spice to world cuisine.

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The earliest traces so far are from southwestern Ecuador, where families fired up meals with homegrown peppers about 6,100 years ago.

The discovery, reported Friday in the journal Science, suggests early New World agriculture was more sophisticated than once thought.

"Some people who have described ancient food ways as being simple will probably have to rethink their ideas because of this work," said lead researcher Linda Perry of the Smithsonian National Museum of Natural History.

"It tells us a lot about what was going on around the prehistoric hearth," adds co-author Deborah Pearsall, an anthropology professor at the University of Missouri-Columbia, who found evidence of chili-laced stew in pots in an ancient Ecuadorean village.

Archaeologists trace food origins not just from curiosity about the ancients' everyday lives. How a crop spreads sheds light on prehistoric travel and trade.

In the Middle East, figs were domesticated 11,400 years ago. Wheat wasn't far behind. In the New World, corn was being cultivated around 9,000 years ago.

How do you trace a pepper, which leaves no husk or other easily fossilized evidence?

A dozen researchers at seven sites around Latin America kept finding microscopic starch grains on grindstones and cooking vessels and in trash heaps.

Perry finally identified these microfossils as residue from domesticated, not wild, chili species that in some spots even predated the invention of pottery.

"We now have a marker, in starch granules, that allows us to look back in time and demonstrate the widespread use of domesticated chili peppers throughout the Americas at much earlier times than previously documented," said botanist W. Hardy Eshbaugh of Miami University in Ohio, a pepper expert not involved in the research.

The microfossils suggest vitamin C-rich chilies were usually mixed with corn and a few other foods, not just used as a spice.

Now the hunt is on for the first site of homegrown chilies. It can't be Ecuador, too far from where wild chilies flourish in Bolivia and Brazil.

"Whether this is migration of people or early trade is one of the fascinating questions," said Pearsall, who calls these early farmers pretty sophisticated. "They were not at the edge of starvation. ... People were growing all kinds of things and not just focusing on staples."