Civilization at the edge of the Tibetan Plateau fell apart—or at least changed very suddenly—4,000 years ago, and now, researchers believe they can explain why. In fact, it has to do with climate change, though not the way we currently think of it, Science 2.0 notes.

Rather than warming, it was global cooling that led to the sudden shift, researchers say in a press release. The changing temperatures prevented locals from growing their key source of food: millet.

That either prompted their departure from the area or forced them to change the way they lived, New Historian reports. Most of those who lived there left, according to Science 2.0, but three centuries later, farmers in the area were growing wheat and barley, which can handle the temperatures.

Jade D'Alpoim Guedes and her team made their findings by looking at data from a different perspective. Experts had been mystified by the apparent shift from millet to wheat in the area, given that previous research suggested millet would have grown well there at the time.

But that conclusion was based on assessing the growing season of millet—rather than the total amount of heat it needs. Guedes' model "turned over previous assumptions," she says.

Now, history seems to be repeating itself: Climate change's effects are being felt particularly acutely in the same region, though this time it's warming rather than cooling.

That means millet could play a big role in the region's agricultural future, Guedes says. (Speaking of cooling, climate change doesn't explain recent harsh winters, researchers say.)

This article originally appeared on Newser: Ancient Global Cooling Could Explain Tibet Mystery

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