Archaeoastronomy of the last forty years reveals that Native Americans of the Chaco Canyon area were extraordinary astronomers, engineers, and builders–in service of a spirituality. What did it mean, and why did they leave the site? We talk to researcher Anna Sofaer and her colleagues.
Archaeologist Robert L. Kelly talks about the evolution of human society, from tools through culture, agriculture, and government. But what’s next … annihilation or a new world?