The delight that children find when they jump in muddy puddles has a surprisingly long history. Fossil footprints discovered at an archaeological site in New Mexico show that a group of youngsters living at least 11,500 years ago spent a few carefree minutes engaged in some joyful splashing. But the world was very different back then: the puddles in question had formed in the deep footprints left by a now-extinct giant ground sloth.
The footprints were discovered at White Sands National Park, a site that is rapidly gaining a reputation for its astonishing archaeology. Within the park, there is a playa – a dried up lake-bed – some 100 square kilometres in size. The playa contains thousands of footprints left by humans, mammoths, sabre-toothed cats and other inhabitants of prehistoric North America. Some of the tracks suggest that humans had reached the Americas 23,000 years ago – about 8000 years earlier than we had thought.
But what really sets the ancient human footprints at White Sands apart is their power to vividly show us what life was like for early Americans. Matthew Bennett at Bournemouth University, UK, has been studying tracks at the site for several years. He and his team can measure the prints to work out things like the age of the person who made them and how fast they were walking or running. Then, they can follow them and see how events such as animal hunts unfolded. “It’s written in the tracks what happened,” says Bennett.
In unpublished work, Bennett and his team have found one collection of prints that tell a particularly evocative tale. It begins with a set of roughly 40-centimetre-long footprints that show a giant ground sloth – measuring perhaps 3 metres from nose to tail – once lumbered across the landscape.
Later, a group of three to five small children showed up. The jumbled mess of footprints they left are focused around one sloth print. The way the children’s tracks deform the sloth print tells us that the ground was wet, says Bennett. It is impossible to be certain about what was going on, but Bennett says the best interpretation is that water had pooled in the sloth print to create a puddle that was perfect for splashing in – an irresistible target for children, even in prehistory.
Kevin Hatala at Chatham University in Pennsylvania says he is excited to learn more about the tracks once they appear in a formal scientific report. “Records like this demonstrate the unique potential for footprints to record information that is extremely difficult, if not impossible, to observe or infer from other materials such as bones and stone tools,” he says.
Kim Charlie and her sister, Bonnie Leno, have made trips to see Bennett and his colleagues at work, studying the prints. They are both members of the Pueblo of Acoma near Albuquerque in New Mexico, one of several groups of Pueblo people who feel a spiritual connection to White Sands.
Charlie is fascinated by the idea that giant ground sloths were so common in the world inhabited by the first humans at White Sands, who may be among the ancestors of the present-day Pueblo people. “It’s fascinating,” says Charlie. “And you think: jeez, were these animals friendly?”
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