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Contact: Kelly Carroll, 575-520-2604
Ghost Fossils at Park Reveal Life and Death Story from the Ice Age
White Sands National Monument, New Mexico – On a remote salt flat with nearby towering, snow white gypsum dunes, a team of scientists are following a string of fossilized footprints back in time to the end of the Ice Age where humans – adults and children - were likely hunting a giant, razor-clawed ground sloth.
The White Sands trackway – a series of tracks and footprints are called a trackway – shows that someone followed a sloth, purposely stepping in their tracks as they did so, said David Bustos, the park naturalist who discovered the trackway 10 years ago.
Team member Matthew Bennett, a professor of environmental and geographical sciences at Bournemouth University in England believes the ancient humans stalked the sloth. “So we ask why? Adolescent exuberance? Possible but unlikely,” Bennett said. “We see interesting circles of sloth tracks in these stalked trackways which we call ‘flailing circles’. These record the rise of the sloth on its hind legs and the swing of its fore legs presumably in a defensive motion.”
At seven- to eight feet tall, tightly muscled and swinging fore legs tipped with wolverine-like claws, the sloth would tear apart any hunter on direct approach. But in addition to tracks of humans following the sloth, there are more human tracks a safe distance away telling scientists that this was a community action making use of distraction and misdirection to gain the upper hand in deadly close-quarter combat.
Bennett believes the tracks show the sloth was turning and swinging at the stalker. “We also see human tracks on tip toes approach these circles; was this someone approaching with stealth to deliver a killer blow while the sloth was being distracted? We believe so. It was also a family affair as we see lots of evidence of children’s tracks and assembled crowds along the edge of the flat playa. Piecing the puzzle we can see how sloth were kept on the flat playa by a horde of people and distracted by a hunter stalking the sloth from behind, while another crept forward and tried to strike the killing blow as the animal turned.”
Bustos said, “The thing that is special about these prints and sets them apart from any other fossil trackways in the world is that this discovery records the interaction between humans and Ice age giant megafauna, and White Sands National Monument has the largest concentration of human and Ice age giant megafauna prints in the Americas.”
There is a great deal more to learn in the years to come, said team member Vince Santucci, the National Park Service’s senior paleontologist. “And we’re pretty motivated to keep looking and studying,” he said. “These fossils are called ghost fossils for a couple of reasons. One, they’re difficult to see at times because of different atmospheric and moisture conditions – and the light has to be just right. And second, the fossil footprints are ephemeral. Once the overlying sand dunes move and reveal the tracks, they start to weather away and can be gone in months.”
High on the list of things to be learned is the question of just when this episode of hunters and hunted took place. The Ice Age ended about 11,700 years ago and the fossil record of ground sloths indicates they were extinct by this time. At White Sands, the scientists used an approach called relative dating to estimate a minimum age for the fossils. “Since the footprints are contemporaneous with animals that died out by the end of the Pleistocene, relative dating tells us those footprints are at least 11,700 years old, or older,” Santucci said.
The team studying and writing about the fossil prints detail their findings today in the journal Science Advances. The multi-disciplinary team of federal, state and academic scientists, technicians and naturalists includes Bustos, the paper’s lead author, Bennett, Santucci and National Park Service archeologist Dan Odess.
Team members visit the remote site under a research permit, but it is a dangerous area of the park’s backcountry that will not be open to the public. Park superintendent Marie Sauter said the team’s documentation – photographs, video, plastic casts of the footprints and other materials will be helpful for park visitors. “We will benefit from their work by using all of this to develop interpretive materials that people can see, touch and experience at the park visitor center or online at National Park Service web sites,” she said.
Footprints preserve terminal Pleistocene hunt? Human-sloth interactions in North America
Alternative Popular Title: How do you stalk and hunt a giant ground sloth?
David Bustos - chief of natural and cultural resources, White Sands National Monument
Jackson Jakeway - White Sands National Monument
Tommy M. Urban - Department of Classics, Tree-ring Laboratory, Cornell University, Ithaca, NY
Vance T. Holliday - School of Anthropology, The University of Arizona, Tucson, AZ
Brendan Fenerty - Department of Geosciences, The University of Arizona, Tucson, AZ
David A. Raichlen - School of Anthropology, The University of Arizona, Tucson, AZ
Marcin Budka - Institute for Studies in Landscapes and Human Evolution, Bournemouth University, Poole, 16 BH12 5BB, UK
Sally C. Reynolds - Institute for Studies in Landscapes and Human Evolution, Bournemouth University, Poole, 16 BH12 5BB, UK
Bruce D. Allen - New Mexico Bureau of Geology and Mineral Resources, New Mexico Institute of Mining and Technology, Socorro, NM
David W. Love - New Mexico Bureau of Geology and Mineral Resources, New Mexico Institute of Mining and Technology, Socorro, NM
Vincent L. Santucci - National Park Service, Geologic Resources Division, Washington, DC
Daniel Odess - National Park Service, Cultural Resources Directorate, Washington, DC
Patrick Willey - Department of Anthropology, California State University, Chico, CA
Gregory McDonald - Bureau of Land Management, Salt Lake City, UT
Matthew R. Bennett - Institute for Studies in Landscapes and Human Evolution, Bournemouth University, Poole, 16 BH12 5BB, UK. 17
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