A US Geological Survey team led by Jeff Pigati and Kathleen Springer analyzed seed layers surrounding human footprints at Lake Otero in White Sands National Park, New Mexico, and found that they coincided with a major warming event that caused lower water levels, exposing ground on which humans and prehistoric animals walked.
The findings also suggest the coexistence of humans and prehistoric animals at a point in time where the phenomenon was previously unknown to have occurred. In addition to the human footprints, tracks were left by giant ground sloths, dire wolves, mammoths, and birds.
"It is an important site because all of the trackways we've found there show an interaction of humans in the landscape alongside extinct animals, like mammoths and giant sloths," said Sally Reynolds of Bournemouth University, who co-authored the study.
"We can see the co-existence between humans and animals on the site as a whole, and by being able to accurately date these footprints, we're building a greater picture of the landscape," she added.
The human footprints are the oldest evidence of human presence in the Americas, according to the University of Arizona. Previously, the only reliable evidence available suggested humans arrived in the region no more than 13,000-16,000 years ago. Based on the size of the footprints, the researchers ascertained that most of them were left by teenagers and children, though a few belonged to adults.
"We can think of our ancestors as quite functional, hunting and surviving, but what we see here is also activity of play, and of different ages coming together. A true insight into these early people," said Matthew Bennett of Bournemouth University, another co-author of the study.