It's Happened Before???

Scientists Solve Mystery of Collapse of Ancient Tibetan Civilization

"Scientists have solved the mystery of the collapse of an ancient civilization living on the fringes of the Tibetan Plateau around 2,000 BC, and it seems that climate change is to blame.

That's at least according to a new study published in the journal Proceedings of the National Academy of Sciences, which details how cooling global temperatures at the end of the Holocene Climatic Optimum - a 4,000 year period of warm weather - would have made it impossible for these ancient people to cultivate millet, their primary food source."

And is was global cooling?????