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The longest trail of fossilized human footprints hints at a risky Ice Age walk

One day in the last Ice Age, a young adult or teenager carrying a child was walking through a muddy floor where mammoths and lazy giants roamed. Now, more than 10,000 years later, fossilized footprints reveal that possibly dangerous journey.

The tracks, found in New Mexico's White Sands National Park, stretch for nearly 1.5 miles down the plain and back, making them the longest set ever found, researchers reported Dec. 1 in Quaternary Science Reviews.

“The length of the track is truly exceptional and gives us a prolonged window into the behavior of individuals,” says evolutionary biologist Kevin Hatala of Chatham University in Pittsburgh, who was not involved in the research. It evokes a personal and intimate connection with our ancestors, as many people today can relate to the feeling of holding a child in their arms, he says.

Scientists came across the discovery when, in 2018, they saw a continuous stretch of dark spots along what was once the shore of the ancient, now dry Lake Otero. A small excavation revealed fossilized human footprints, as well as those of a mammoth and a terrestrial sloth.

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Of the 427 human footprints discovered, the researchers analyzed 90. The size and depth of the footprints suggest they were made by a teenager or a young woman, the researchers say. Uneven impressions hint that the surface was slippery and that on one of the legs of the trip, at times, the person was moving a heavy load. That load seemed to be a child: smaller prints of perhaps a 3-year-old appeared next to the larger footprints at various points.

"It looks like the person was in a hurry, we don't know why. It was a brisk walk and it looks like the person was tired … but he kept going," says David Bustos, a biologist at White Sands National Park.

fossilized human footprintsA set of fossilized human footprints (foreground on the right) found in White Sands National Park in New Mexico stretch about 1.5 miles along what was once a lake. The person followed the same route back and forth (left) during the last Ice Age.MR Bennett et al / Quaternary Science Reviews

That hurry may have been due to the risk of the trip. The footprints of the area found above came from groups of people (SN: 25/04/18). They probably moved in groups to hunt animals like mammoths, sloths and wolves safely, Bustos says.

In this case, the footprints of a mammoth and a terrestrial sloth crossed human footprints; at some points, human footprints came first while at others, the human stepped on the footprints of other animals. Based on when those animals became extinct, researchers were able to outline human footprints to the last Ice Age.

While it’s unclear if the mammoth detected the human presence, the lazy giant climbed on its hind legs and moved in circles, suggesting it knew there was a human nearby, researchers say. It is possible that such animals were in regular contact with humans, Hatala says.

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