Footprints found at White Sands National Park in New Mexico provide the earliest unequivocal evidence of human activity in the Americas and provide insight into life over 23,000 years ago.
The footprints were formed in soft mud on the margins of a shallow lake which now forms part of Alkali Flat a large playa at White Sands. Researchers from the US Geological Survey dated these tracks using radiocarbon dating of seed layers above and below the footprint horizons. The dates range in age and confirm human presence over at least two millennia with the oldest tracks dating from around 23,000 years ago.
Drs Jeff Pigati and Kathleen Springer of the US Geological Survey undertook the dating, Kathleen Springer said, “Our dates on the seeds are tightly clustered and maintain stratigraphic order above and below multiple footprint horizons – this was a remarkable outcome.” This corresponds to the height of the last glacial cycle, during something known as the Last Glacial Maximum, and makes them the oldest known human footprints in the Americas.
The footprints tell an interesting tale of what life was like at this time, with the tracks left mainly by teenagers and younger children, with the occasional adult judging by their size. Tracks of mammoth, giant ground sloth, dire wolves and birds are all present at the site as well. Dr Sally Reynolds, a Principal Academic in Hominin Paleoecology at Bournemouth University, said, “It is an important site because of all of the trackways we’ve found there show an interaction of humans in the landscape alongside extinct animals like mammoths and giant sloths. 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.”
The tracks at White Sands were first discovered by David Bustos Resources Manager at the National Park. He said, “It is incredible to have the confirmation on the age of the human prints, and exciting but also sad to know that this is only a small portion of the 80,000 acres where the prints have been revealed bare and are also being rapidly lost to ongoing soil erosion.” The team also pioneered non-invasive geophysical techniques to help locate the site. Dr Tommy Urban, from Cornell University led this part of the work, and said, “Detection and imaging with non-destructive technology has greatly expanded our capacity to study these remarkable footprints in their broader context”.
It was previously thought that humans entered America much later, after the melting of the North American ice sheets, which opened up migration routes. However, the footprints now show a much earlier migration of humans into the Americas.
Professor Vance Holliday of the University of Arizona said, “There has been a lot of debate over many years about the first peopling of the Americas with several early sites identified. Few archaeologists see reliable evidence for sites older than about 16,000 years. The White Sands tracks provide a much earlier date.”
Dr Dan Odess of the National Park Service said, “White Sands provides the first unequivocal evidence for human presence in the Americas during the Last Glacial Maximum. Not all archaeological sites contain such unequivocal evidence. One reason why this discovery is important is that it makes the idea that other purportedly ancient sites really are evidence for human presence that much more plausible, even if the evidence they contain is less unequivocal. This doesn’t mean all of those sites are legitimate, but it means they cannot be dismissed out of hand.”
Professor Matthew Bennett from Bournemouth University, who helped lead the study said, “The footprints left at White Sands give a picture of what was taking place, teenagers interacting with younger children and 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.”
Traditional archaeology relies on the discovery of bones and tools but can often be difficult to interpret. Human footprints provide unequivocal evidence of presence and also of behaviour. Professor Bennett added, “The icing on the cake here is that we can date these traces accurately using beds of ditch grass seeds.”
The research was undertaken by researchers from Bournemouth University, the National Park Service, U.S. Geological Survey, Cornell University, and the University of Arizona.
The research is published in Science.