THESE TRACK, from a dry lake bed in New Mexico, are one of many assemblies that radiocarbon evidence suggests were made between 21,000 and 23,000 years ago. They are described in the Science by Matthew Bennett of the University of Bournemouth, Great Britain, and colleagues, and are the oldest undisputed evidence of humans in North America. Little doubt that the first Americans crossed Asia, probably through the Bering Strait when low sea levels during the last Ice Age meant it was dry land. The exact timing, however, is unclear. The oldest human fossils in North America date back to 13,000 years ago. But evidence of stone tools suggests the presence of people 30,000 years ago. The evidence for the stone tool is, however, controversial. Such tools are difficult to date directly and can be moved in sediments older than the date of their creation by animal activity. Footprints, on the other hand, stay put.
This article appeared in the Science & Technology section of the print edition under the title “Old lake bed reveals evidence of America’s first inhabitants”