A YOUNG woman is struggling across a muddy plain with a 3-year-old child on her left hip. She puts the youngster down to catch her breath. But she is too afraid to pause for long. The pair are alone, an easy target for the sabre-toothed cats that may lurk nearby. She picks up the child again and hurries on, vanishing into the distance. For a time, all is quiet. Then a giant ground sloth plods across the path she took. The animal catches the woman’s scent and is instantly on guard, rearing up and turning to scan the landscape for human hunters.
What was it like to live in the Stone Age? There must have been moments of joy, fear, love, pain and perhaps even wonder for the people who inhabited Earth tens of thousands of years ago. But emotions don’t fossilise, so we are shut out of those moments, separated by a vast chasm of time. We can find all the bones and tools we like, but they won’t tell us about the experience of life for our ancient ancestors.
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Then again, a new window on their everyday existence may be cracking open. As people went about their lives, they left untold numbers of footprints behind. These recorded their behaviour in a unique way, capturing everything from nervous shuffles to determined sprints. What’s more, the tracks have an order to them, meaning events can be read like a narrative. That story of the woman, the child and the giant sloth is a vivid example we have found written in ancient tracks – but it certainly isn’t the only one. An explosion in discoveries of ancient footprints is revealing a new portrait of the past, from the division of labour between the sexes to the behaviour of long-extinct animals.
Archaeologists have known for decades that footprints can fossilise. In 1976, for instance, a research team at Laetoli, an archaeological site in Tanzania. They were instantly important for showing that an early species of hominin called Australopithecus afarensis – of which the best-known example is a fossil named Lucy – walked on two legs rather than on all fours, as some had argued.
At the time, footprints were seen as a useful source of evidence for basic anatomical facts about a species, plus where and when it lived. Even so, the discovery at Laetoli didn’t trigger a rush to find more ancient prints. “It was thought they were really rare,” says .
The fact that few researchers looked for more was unfortunate, says Bennett, because ancient footprints are actually common. They were produced in enormous quantities, perhaps a million per person each year, so even though only a tiny proportion will have ended up as fossils, that is still a lot. “My bones have one opportunity to make it into the fossil record,” says , Pennsylvania. “But all the steps I take every day – I have an enormous opportunity to make it into the fossil record that way.”
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One way footprints can end up being preserved is if a person walks over a blanket of ash from a volcanic eruption, which then hardens like quick-drying concrete on exposure to moisture. This is how the Laetoli footprints fossilised, but it is a rare process. It is far more common for footprints in wet sand or mud to get quickly covered with dry sand and dust blown in by a storm. These get buried and fossilise, and then geological processes can push them back up to the surface.
Although ancient footprints were a low archaeological priority for decades, things are finally changing. The past 20 years have seen an eruption in the number of ancient footprint sites. They can be found in almost every corner of the world – in Africa, Europe, , Australia and the Americas.
Following the trail
It is also becoming clear that footprints can paint a surprisingly intimate picture of the past. For instance, it is well-established from lab experiments that the size and shape of someone’s foot can predict their body size fairly accurately. And since body size generally differs between the sexes, you can potentially estimate the sex of the individual who made a set of footprints. Foot length is also , while the distance between prints made by the same foot allows you to estimate someone’s walking or running speed. “Footprints are reflective of how tall you are, your age, your sex, potentially even your weight,” says archaeologist .
All these factors came together during at a site in Tanzania called Engare Sero. Hatala and his colleagues used deductions from the prints to reconstruct a scene from roughly 12,000 years ago. They found the tracks belonged to at least 17 people from our own species, Homo sapiens, making this the largest collection of ancient human prints ever found in Africa. The researchers concluded that the group was probably comprised of 14 women, two men and a youngster. All members of the group were walking at the same speed – a leisurely 1.2 to 1.5 metres per second – which suggests they were travelling together.
Armed with this kind of evidence, we can begin to make educated guesses at what these people were up to. In modern hunter-gatherer communities, groups of women often work together to forage for food. This could be what was going on in the ancient group. If so, it tells us something about the division of labour between the sexes at the tail end of the Stone Age. “I don’t know how you would potentially observe that sort of social dynamic using any other line of archaeological evidence,” says Hatala.
Some of the most thrilling footprints to emerge so far were found at a site called White Sands National Park in New Mexico. This isolated area is surrounded by a missile range and has spectacular dunes and salt flats that make it popular with film-makers. It contains a huge playa, or dried-up lake, where we have long known there are fossilised footprints from ancient animals. In 2017, David Bustos, who works with the National Park Service at White Sands, discovered human footprints. Shortly afterwards, Bennett travelled there to search for more prints. He has been investigating intensely ever since.
“Most of the trackways at White Sands involve a couple of adults and a gaggle of children,” says Bennett. The trails typically meander across the landscape, the sort of thing you would expect from a family on a Sunday afternoon stroll. But one set that Bennett, Bustos and their colleagues came across was different: tracks of a single person striding out in a straight line. These would prove to be the prints that told the story of the young woman, the child and the ground sloth. But Bennett and Bustos didn’t know that when they first set out to follow the trail.
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Soon, they realised there were actually two sets of tracks: one heading roughly north for at least 1.5 kilometres; the other, less than a metre away, taking the same route south. They deduced that the northerly prints came first because they are crossed and partially distorted by footprints left by two large, now-extinct animals, a mammoth and a giant ground sloth. The human southerly prints, by contrast, sit on top of the animal footmarks.
Statistical analysis showed no clear difference in the size and shape of the northerly and southerly prints, so they were probably left by the same person. The fact that this individual didn’t deviate from their course on either journey is significant, says Bennett. “It says: I’m on a mission.”
Who was this person? Bennett and his team established that the prints were left by a slender individual, probably a young woman. It is also clear she was in a hurry. Running the numbers, her pace was clocked at 1.7 metres per second, which is faster than the average modern walking speed. It is particularly brisk given that the going was tough – the footprints record plenty of evidence that the woman slipped as she hurried on her way. “There was urgency of movement,” says Bennett.
Special delivery
What was her mission? On the northerly journey, some of the prints from her left foot show a rotational slip in the soft mud, giving them a banana shape. Bennett suspects she was unbalanced on her left because she was carrying a burden on her hip. At a few points along the northerly trackway, we catch a glimpse of that burden: there are a handful of footprints belonging to a child of no more than 3 years old. It appears the woman was carrying the child and occasionally put them down, perhaps to rest or to give the child a break.
We don’t know the woman’s destination. The northerly prints vanish into the White Sands missile range, beyond the reach of investigation. But there are no indications that the woman was still carrying the child in the southerly prints. One interpretation of the events is that she was delivering the child to someone. Whether she succeeded or not, she returned alone.
Stories like this mean a lot to Kim Charlie and Bonnie Leno. 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 a committee member of the regional Tribal Historic Preservation Office, while Leno, her sister, is a designated tribal monitor, meaning she collaborates with scientists to share her traditional knowledge of the area. Both have visited White Sands to see the archaeologists at work. “It’s just fascinating,” says Charlie. “There are no words to describe how you feel when you’re actually there.”
The fact that Leno discovered some footprints herself during the visit – a human print near one left by a giant sloth – only added to the excitement. With her knowledge of the region, Leno already has a strong sense of where people once lived and where they travelled. “You could say we see things beyond the archaeologists’ view,” she says. “That could be because these were our ancestors.” There has also been at least one case where a partnership between researchers and people with traditional knowledge has helped interpret the meaning of footprints (see “Cave of the sacred bison“).
Bennett stresses there is always a risk of pushing footprint analysis too far in pursuit of a captivating story – what he calls “palaeo-poetry”. It is tempting to argue that the woman hurried because she was wary of roaming sabre-toothed cats, but we will never know for sure. Still, footprints do pitch us closer than ever to the emotions of ancient people.
The evidence does strongly suggest that fear hung in the air that day, and maybe in more than one species. The giant ground sloth acted oddly when it crossed the woman’s northerly tracks. Its own footprints show that it reared up on its hind legs and shuffled around in a circle. The obvious conclusion, says Bennett, is that it had picked up the woman’s scent and, anxious about the possible presence of hunters, was scanning the landscape. This might have been typical sloth behaviour, says Bennett. There are plenty of other ground sloth tracks elsewhere at White Sands. They show that the beasts usually trundled in a roughly straight line, he says. But some trails are different. “Suddenly, the prints do an about-face and head off at a different angle,” he says. “And when we look at that point of inflection, we’ll find a human footprint.”
Landscape of fear
One collection of prints at White Sands, described by Bennett, Bustos and their colleagues in a 2018 study, even , with humans literally walking in the animal’s footprints before attacking. But if sloths did fear humans, the same doesn’t go for some other animals. Mammoths and even camel trails don’t deviate when crossing human trackways, telling us they had a more relaxed attitude to early Americans. “It’s really breathing life into these animals,” says Bennett.
The footprints at White Sands aren’t all about the gruelling struggle to survive though. In unpublished work, Bennett and his team have discovered some that seem to record a moment of pure joy. The researchers found a chaotic mess of footprints belonging to a gang of children, the oldest no more than 6 years old. The tiny prints are focused around the large impressions left by yet another ground sloth. The logical conclusion, says Bennett, is that the children were splashing in the muddy puddles left in the deep sloth footprints. “Kids have always liked to jump in puddles,” says Bennett. “These are stories that can connect people with the past.”
Beautiful tales aside, footprints still have the capacity to throw up surprises about the grand sweep of human history. It turns out White Sands might end up at the centre of one much-debated question: when did humans first begin to populate north America?
For decades, it was assumed the first settlers were connected to a style of stone tool first found at another site in New Mexico called Clovis. Today, the consensus is that the Clovis culture – which is about 13,000 years old – isn’t the earliest evidence of human activity in the Americas. Instead, the accepted archaeological and genetic evidence suggests people began living there about 15,000 years ago. But there is a nagging suspicion this isn’t the final answer. A number of archaeologists have found evidence that they claim shows humans were in north America thousands of years earlier, at the peak of the last glacial period. However, the evidence is contested.
White Sands is throwing up new clues. The whole area is composed of layers of rock of different ages that are exposed in different places. One day, Bennett and his colleagues found a set of human tracks padding across the dirt and vanishing beneath a small hill. This suggested the tracks were older than the hill – particularly ancient, then. Crucially, the researchers could test their hunch, because the dirt around the prints contained grass seed that could be radiocarbon-dated. In September 2021, they reported the results: . It is the most incontrovertible evidence yet that the peopling of America took place much earlier than we thought.
“White Sands is a fantastic discovery,” says , who has also found archaeological evidence suggesting that humans were in the Americas much earlier than 20,000 years ago. He doesn’t think ancient footprints should overshadow traditional artefact-based archaeology. But he has previously suggested that White Sands might come to be seen as pivotal in the story of the earliest Americans.
This kind of legacy doesn’t interest Bennett. But he does hope the work at White Sands will encourage other archaeologists to go looking for footprints elsewhere in the region. Because the most remarkable part of this story is that White Sands might prove to be unremarkable in the grand scheme of things. “There are many other playas in the American south-west,” says Bennett. This means there could be millions of other fossilised human trackways out there, waiting to tell their ancient stories of what life was like in the deep past.
Cave of the sacred bison
If you want to read information from footprints, it pays to turn to the experts. People from some Indigenous communities depend on their ability to track animals during hunts. This fact hasn’t been lost on scientists.
For more than a century, archaeologists have puzzled over 17,000-year-old human footprints found in the Tuc d’Audoubert cave in southern France. Many of the prints were made using the heels only, leading to the suggestion that they may be evidence of some ritual, linked to a nearby sculpture of two lifelike bison.
In 2013, a European team invited three Ju/’Hoansi trackers from Namibia to take a look. “They told me it was a challenge,” says Dam Debe, a Ju/’Hoansi tracker and a colleague of the trio. The footprints were far older than those the trackers normally encounter.
They did, however, in the cave millennia ago. The prints are those of a teenager and a man in his 30s who were busily collecting clay from a small pit in the cave floor to make the bison sculpture.
Why did they walk on their heels? Because, said the trackers, a knowledgeable person can recognise a member of their community from their full footprint. Walking on the heels is awkward, but it is an effective way for someone to conceal their identity – which might have been important to the sculptors if the artwork had ritual significance.
“I feel that the approach the trackers employ is similar to the methods used by Western scientists,” says Megan Biesele at the Kalahari Peoples Fund in Austin, Texas, who witnessed the trackers at work in France.
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