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SAN FRANCISCO - Chilli peppers have achieved the culinary accolade of being the oldest-known kitchen condiment after scientists found evidence that people were cooking with them more than 6000 years ago.
An archaeological study has discovered that hot chilli peppers were added to change the flavour of otherwise bland-tasting food long before the construction of the first pyramids in ancient Egypt.
The first people to cook with chili peppers lived in the lowland areas of what is now Ecuador, but the spicy treat soon spread through South and Central America.
It went global after the Spanish conquistadors arrived in the New World.
The study was published this week in the journal Science.
When the first Europeans came to the Americas, various varieties of chili peppers were widely grown as a crop throughout the New World.
But scientists knew little about when or how it became such an important feature of the diet.
Part of the problem was that vegetable matter quickly degrades and is lost to scientific analysis.
But Linda Perry of the Smithsonian Institution's National Museum of Natural History in Washington solved the problem with the discovery that peppers could be identified at an archaeological site from tiny fossilised grains of starch.
"Sorting through microscopic particles and finding a type that distinguishes such an important plant group is like opening a window to the past," Dr Perry said.
"Suddenly we are able to gain incredible insight into ancient agriculture, trade and cuisine by making these plants visible nearly everywhere they occurred."
The oldest starch grains from chilli peppers were found at two sites in Ecuador dating to 6100 years ago.
Grains have also been found as far afield as the Bahamas, Panama and Peru.
"Before our research, there wasn't much archaeological evidence to show that prehistoric people in Central and South America were eating domesticated chilli peppers," said Deborah Pearsall, professor of anthropology at the University of Missouri-Columbia in the US.
"Chili peppers don't preserve well because when you cook with them, you eat most of them; you don't have husks or shells that are thrown away and preserved.
"That's why we used a technique that involved analysing microscopic starch grains on cooking and grinding tools to find this new evidence.
"We knew from historic and ethnographic records that people were eating domesticated chilli peppers, but this archaeological evidence confirms those findings.
"It also shows us that chilli peppers are one of the oldest domesticated food sources in the Americas and that people in distant areas all ate them."
Chili peppers belong to the capsicum group and are technically classed as fruits.
Scott Raymond, of the University of Calgary in Canada, who took part in the study, said growing chilli pepper as a crop probably occurred in the lowlands of South America, rather than the highland regions associated with the Aztec and Inca cultures.
And he sees a simple reason for its worldwide popularity.
"Chilli is an excellent disguiser. If something's not tasting quite right, you can always throw a few chilli peppers into the pot."
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