Mapmakers once thought the earth was flat. Astronomers used to believe the sun circled the earth. As late as the 1990s, archaeologists were convinced that the original American settlers crossed a land bridge from Asia into Alaska, found daylight between the glaciers, and gradually followed it south. According to what had been orthodox thinking, that happened about 12,000 years ago. “Suppose it were true,” says Jack Rossen, associate professor and chair of the Department of anthropology. “Suppose you could find a corridor through a mile-high wall of ice and follow it for a thousand miles. What would you eat? Popsicles?”...
