for National Geographic News
The Spanish conquistadors toppled the Inca Empire in the 16th century in their quest for silver and gold. They returned to Europe with a different sort of earthly nugget dug from the elaborate terraces sculpted into the sides of the Andesthe potato.
Potatoes have since spread to nearly 150 countries around the world; hundreds of millions of tons are grown annually, and the potato has become a staple in the world's diet.
But in the Andes, where the potato got its start, market forces, years of drought, and changes in cultural priorities are eroding the status and the diversity of the potato.
Nearly 4,000 different varieties of potato can be found in the Andes, and scientists, economists, and historians are racing to record and preserve the genetic diversity to ensure it does not disappear as suddenly as did the Inca Empire.
Scientists believe wild tubers were first domesticated around 8,000 years ago by farmers who lived on the high plains and mountain slopes near Lake Titicaca, which borders modern day Bolivia and Peru. The tubers grew well in the cold, harsh climate and quickly took root as a centerpiece around which life revolved.
The potato "is considered to have been a pillar of Andean culture since domestication," said Merideth Bonierbale, head of crop improvement and genetic resources at the International Potato Center (CIP) in Lima, Peru.
Ritual ceremonies marked by singing, dancing, and drinking still take place throughout the year to ensure a successful harvest. Young men playfully drag young women across potato fields to make the land fertile. Cow horns and flutes are played to cheer on the plants and bring rains.
"There are also ways in which Andean farmers divine the state of the year, which crops will do best, and where it is better to cultivate them: In the high puna or the lower valleys," said Denise Arnold, a researcher at the Institute of Aymara Language and Culture (ILCA) in La Paz, Bolivia.
For example, farmers from the Aymara and Quechua regions of Bolivia and Peru time the planting of their potatoes on the clarity of a constellation of stars known as the Pleiades.
When the constellation is bright and clear, the farmers expect early and abundant rains and a bountiful potato harvest and plant their crops in October. If the constellation is obscured by high cirrus clouds, the farmers anticipate drought and postpone their planting until November or early December.
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