Human poop can reveal more than you might think, even when it's really, really old. In a new study of a Central American Maya civilization, samples of ancient feces have shown how the size of this community varied significantly in response to contemporary climate change. Researchers identified four distinct periods of population size shift as a reaction to particularly dry or particularly wet periods, which haven't all been documented before: 1350-950 BCE, 400-210 BCE, 90-280 CE, and 730-900 CE. In addition, the flattened poop piles show that the city of Itzan – which in the modern day would be in...