Incredible details of 10,000-year-old hike revealed in fossil footprints

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Over 10,000 years ago, a woman or young man – a toddler balancing on one hip – set out on a relentless journey north through what is now White Sands National Park, New Mexico. The rain may have touched the traveller’s face as his bare feet slid across the mud. They paused to briefly put the toddler on the floor before continuing; a woolly mammoth and a giant sloth strolled along their newly mapped tracks. Several hours later, the traveler followed the same route south, this time empty-handed.

Now, a team of scientists have documented nearly a mile of the company’s fossilized round-trip footprints – the longest human trail ever found in its time. “I’ve never seen anything like it,” says Kevin Hatala of Chatham University, an evolutionary biologist who was not on the study team.

The trail consists of more than 400 human footprints, including several tiny children’s footprints, as described in a new study published in Quaternary Science Reviews. By analyzing the shape, structure and distribution of the tracks, the research team unveiled an intimate portrait of an ancient person’s walk across the landscape, to the toes gliding over the smooth surface.

Scientists carefully dig up ancient footprints embedded in the sand before recording them in three dimensions. The structures are extremely delicate and decompose quickly when exposed.

Courtesy of NPS and Bournemouth University

The team also discovered traces of a mammoth and a giant sloth crossing the area after humans had passed. The mammoth didn’t seem concerned about any humans nearby, but the giant sloth probably noticed. The tracks suggest he was raised on two legs, possibly to detect human presence, as bears behave today.

“It gives us a sense of the humans within their ancient ecosystem,” says study author Sally Reynolds, a paleontologist at Bournemouth University. It highlights the apparent lazy awareness of nearby humans. “It’s an idea you won’t get from the bone.

The ghost tracks

Fossil prints are a boon to scientists, preserving stunning snapshots of ancient behavior that cannot be gleaned from other remains. “Fossils are obviously the backbone of understanding past life,” says paleoanthropologist William Harcourt-Smith of the City University of New York, who was not part of the study team. “But the fingerprint sites are special because they are at this precise moment.”

The new trail site is part of an ongoing effort to document the treasure trove of ancient carvings at White Sands National Park – an endeavor driven by the careful observations of David Bustos, the park’s resource program manager. Superficial impressions are difficult to spot, revealed only by slight changes in humidity, which cause slight changes in color.

“He kept noticing those ghost tracks, those footprints, coming to light,” Reynolds said of Bustos’ sightings.

In 2016, Bustos interviewed a range of track specialists, including the first author of the new study, Matthew Bennett, a geologist at the University of Bournemouth in England. Bennett and his colleagues have since made several trips to White Sands, documenting the range of prints – human and animal – in each section of the park.

The prints in the new study are pressed into fine sand, and a thin crust of salt is all that holds their shape together, Reynolds says. The team carefully searched 140 of the tracks, using a paintbrush to reveal the delicate structures. Yet these fragile shapes quickly decompose once discovered, so the team recorded each print with a series of photographs to build a three-dimensional model, a technique known as 3D photogrammetry.

“As soon as we display them, the race is really on to save them before they… disappear,” Reynolds says.

Tiny prints

By studying the shape, size and distribution of the footprints, the researchers attempted to piece together what happened on the ancient walk on the muddy ground. The main lead maker could have been a woman aged 12 or older, or perhaps a young man, based on a comparison of footprint lengths with modern humans. At at least three points along the way, tiny footprints join the main track, evidence of a child under three.

The track spacing suggests the person was traveling at about 3.8 miles per hour. Although it wasn’t a jog, it would have been a rushed pace given the muddy conditions and the heavy load, Hatala notes.

In some places, the traveller’s strides were unusually long, as if he was walking or jumping over an obstacle. “It could be puddles. “

The child, however, was carried only one way. During the northbound trip, the left foot tracks are slightly larger, which may be the result of the toddler being carried on one hip. Among the northbound trails there are also instances where the hiker ‘s toes glide over the muddy surface, the foot dragging to create a banana shaped impression. However, on the return to the south, this difference in the size of the tracks is not apparent, and the sliding much less frequent, suggesting that the walker was not congested.

The researchers had previously suggested that the differences in the prints of the right and left foot could be evidence of a load being carried, but this was often speculation. The new study offers a bit more evidence: “In this particular case, you see a child’s footprints suddenly appearing halfway through,” Hatala says.

The animal tracks helped the team estimate when the adventurer crossed the country. After the northbound journey, the mammoth and giant sloth crossed the new trail, while the southbound human footprints intersected those of the animals. This overlay shows that all prints were deposited within a few hours before the mud completely dried. The presence of these now extinct creatures alongside humans suggests that the ancient adventure took place at least 10,000 years ago.

‘Just like us’

In 2017, Reynolds, who is married to Bennett, was pregnant at home when Bennett called her to tell her about the long series of footprints. “He was over the moon,” Reynolds recalls. They were particularly won over by the old child taken away for the ride. “Those tiny little fingerprints were so unexpected,” she says. They called the trails “Zoe’s trail” after the name they planned to give to their unborn daughter.

Much remains unknown about the former adventurer. Where was the plotter going? What was the purpose of the trek? What happened to the child?

The plotter seemed to know the route well, Reynolds said, perhaps following a path to the camp of another family or group of hunters. “There was no procrastination, of getting lost,” she said. But the end point of the trip remains unknown, as impressions point to what is now the White Sands missile base, which is inaccessible to researchers.

The behavior recorded on the track is perhaps not surprising, says Harcourt-Smith. One would expect humans to bear children: “All cultures do; parents of monkeys do, ”he says. But at the same time, there is a certain relatability to the discovery.

“It’s a reminder that these people were like us,” he says. “Maybe different daily individual stresses – we don’t have mammoths walking around – but they walk around the landscape the same way we would.

The research team continues their work at White Sands National Park, bringing together a nuanced look at the area’s former residents. “These are little snapshots of ancient life and attitudes towards other animals and landscapes that we just never thought we could get,” says Reynolds. Over time, more stories – and certainly more mysteries – will be uncovered.

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