Preserved in the gypsum playa in White Sands.
Bennett and his colleagues were able to accurately date 61 footprints by radiocarbon dating layers of aquatic plant seeds that had been preserved above and below them. The prints, which were discovered in the Tularosa Basin in White Sands National Park, were made 21,000 to 23,000 years ago, the researchers found.
The timing and location of the prints in southwestern North America suggests that humans must have been on the continent much earlier than previously thought, Bennett said. The people who made the footprints — mostly teenagers and children — were living in New Mexico at the height of the last Ice Age.