A team led by Joyce White of the School of Arts & Sciences studied stalagmites in a Laotian cave and identified a drought that lasted for more than a millennium, one of a series of megadroughts that affected Asia and Africa between 4,000 and 5,000 years ago.
https://www.sciencemag.org/news/2020/08/ancient-megadrought-may-explain-civilization-s-missing-millennia-southeast-asia Science