Roughly 1,000 years ago, ancient peoples carried more than 200,000 heavy timbers entirely on foot to a site in the modern-day Four Corners region called Chaco Canyon. ÍÃ×ÓÏÈÉú´«Ã½ÎÄ»¯×÷Æ· researchers think they know how such a feat of human endurance may have been possible.