It's one of the great mysteries of civilization: what killed off the Mayans? Archeologists have pointed to warfare, but a new report, published in Science, shows that the collapse of the Mayans might have been related to a "modest reduction in precipitation." In other words, a mild drought may have been enough to kill them off. Scientists have thought that a severe drought might have done it, but the researchers show a sustained 25 to 40 percent drop in rainfall could have exhausted water supplies for crops, leading to the end of the Mayans in 900 AD.
