A hunter-gatherer who trekked through a desert oasis a hundred centuries ago left the continent’s most lasting impression: the oldest known human footprints in North America. There are only two of them — one left and one right — but the ancient traveler’s path through mineral-rich sediment in the Chihuahuan Desert allowed them to become enshrined in stone, and now dated, some 10,500 years later... The tracks were first discovered during highway construction in northeastern Mexico, about 300 kilometers from the Texas border, in 1961. They were excavated and taken to a local museum for study, but their precise location...