Researchers studying a trail of fossilized footprints on a remote New Mexico salt flat have determined that the tracks tell the story of a group of ice age hunters stalking a giant sloth.
Scientist David Bustos said the tracks, both adult and children’s footprints found at White Sands National Monument, showed people followed a giant ground sloth, purposely stepping in their tracks as they did so.
The team studying the fossil prints detailed its findings in the latest edition of the journal Science Advances. The publication has drawn attention to White Sands – home to the world’s largest field of white gypsum sand dunes – as members of New Mexico’s congressional delegation push to turn the monument into a national park.
White Sands contains a sizeable collection of fossilized tracks, including saber-toothed cats and wooly mammoths. It is unclear why ancient humans would have stalked the sloth, said team member Matthew Bennett, a professor of environmental and geographical sciences at Bournemouth University.
Two human footprint trackways. Photograph: Reuters
The creature standing at 7ft to 8ft (2m) tall with long arms and sharp claws – would have had a distinct advantage in close-quarter encounters.
“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 forelegs presumably in a defensive motion”.
Scientists said there were more human tracks a safe distance away, telling them this was a community action. Bennett said: “We also see human tracks on tiptoes approach these circles. Was this someone approaching with stealth to deliver a killer blow while the sloth was being distracted? We believe so”.
There is a great deal more to learn, such as when this episode of hunters and hunted took place, said team member Vince Santucci, a senior paleontologist with the US National Park Service.
The ice age ended about 11,700 years ago and the fossil record of ground sloths indicates they were extinct by then. At White Sands, 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.