An anonymous footprint in sand. Photo: Kensy Cooperrider

It began with a bang — an eruption, to be exact. Around 3.6 million years ago, in a region now known as Laetoli, in Tanzania, a volcano belched out a fearsome cloud. It was a violent upheaval no doubt. But soon, as the cloud settled, creatures of all kinds resumed their daily commutes, to-ing and fro-ing through the ash. They stamped out a fray of footprints — more than 18,000 tracks all told, from 17 different families. Cats and hares and baboons are all in evidence. Antelope and rhinos, too. There are signs of a now-extinct three-toed horse and of the microscopic march of what may have been a dung beetle.

It was Mary Leakey, an archaeologist working in Laetoli in the 1970s, who first described this sprawling menagerie of marks. She and her team were especially interested in a subset of the tracks made by a trio of hominids — early humans, that is. That tracks show that their foot-shape was unmistakably like our own; that their stride had a familiar cadence. The path this trio laid down — about 70 steps in all — is what archaeologists refer to as a trackway. And this one shows that our ancestors were, already three and a half million years ago, walking upright, bipedally. These now-famous Laetoli footprints, in other words, may amount to just a few small steps, but they speak to one our species’ most giant leaps.

Tracks tell stories. Stories writ in snow, mud, or dust — tramped out along riverbanks, over dunes, across shorelines. And these tales, under the right conditions, have astonishing durability. They can reach across vast stretches of time to tell about our origins and much else besides.

Since the Laetoli finds, other remarkable trackways have emerged. In 2013, some 50 footprints came to light in Norfolk, England. Dating to around 800,000 years ago, they likely belonged to Homo antecessor, a species of archaic humans that predated the Neanderthals in Europe. The footprints are the oldest hominid tracks ever found outside of Africa, in fact, and they speak to a human family very much on the move. They were made by a mixed band adults and children — five or so individuals — who may have been scouring the mudflats for shellfish and other coastal snacks.

Two views of the Happisburgh prints, with lens cap for scale. Photo by Martin Bates. Source: Wikipedia. (CC BY 4.0)

Even more recently, in November of 2020, a team working in the White Sands Monument of New Mexico announced the longest ancient human trackway ever found. It’s made up of 400 or so prints and extends for 1.5 kilometers across a muddy playa; their age is hard to pinpoint, but they are thousands of years old. The prints were likely made by a young woman carrying a toddler at her hip, and, from her gait, it seems she was making a bee-line. This may be because she and the child had company. Mammoths crossed their path in a few places. A giant ground sloth was roaming the area, too. Its own tracks suggest that one point it reared up on its hind legs to sample the air, perhaps detecting a whiff of human.

The branch of archaeology devoted to tracks is known as ichnology, from the Greek word ikhnos for ‘footprint.’ This subfield is, by all accounts, as lively as ever. But it’s not just trained archaeologists who are interested in tracks. Hunters, famously, are intensely curious about them. They memorize their shapes and patterns, study how they fade and persist. They have their own colorful parlance, too. Contemporary hunters often refer to tracks as ‘spoor’; but at one time they were known — more evocatively — as ‘foils.’ Some argue that hunters have been tuned to tracks for thousands, maybe even millions of years. And a few venture the bold claim that tracking was central to how we became human.

The scholar Kim Shaw-Williams has made this case in detail. In a 2014 paper in the journal Biological Theory, he presented what he dubs the “social trackways” theory of cognitive evolution. His account starts with the Laetoli footprints. He lingers on a detail about them that is perfectly easy to overlook. At first blush, the trackway consists of just two sets of prints — but in fact there are three individuals in the mix. That’s because one of the individuals was stepping — quite precisely, it seems — in the footprints of another.

To Shaw-Williams, this detail is telling. Stepping perfectly in another’s footprints is not so easy to do — it requires concentration. We can’t say whether the tracks were made at exactly the same time — it could be that one individual was tracking down the other at some later point. In any case, it seems that, already at that very early stage, we humans were tuned to tracks left by our conspecifics. Even a very rudimentary awareness of other people’s tracks could come in handy — when needing to re-trace steps over unfamiliar terrain, for instance. Other advantages of track-reading would kick in later, once we started to key on the tracks of other species. We may have done this not just while hunting, but also when searching for water holes, trying to avoid predators, or scouting for tubers. On Shaw-Williams’ account, tracks were a key part of our niche and the ability to read them would have been directly selected for. This wouldn’t have been selection for narrow ability — like being distinguish an antelope from an ostrich print — but rather for rich capacity. A capacity for imagining events we haven’t experienced; for reasoning about invisible agents and forces; for putting ourselves in the shoes, or hooves, of others.

The argument hinges on a key claim: that only humans read tracks. Many species follow scent trails, of course, but only humans seem follow visual trails. Chimps, for example, are reportedly unmoved by footprints. The issue has been addressed most directly with dogs, through a series of studies by comparative psychologist Deborah Wells. One of her experiments showed that some dogs were consistently able to follow human trails. But a follow-up experiment with a reversed trail — made by a human walking backwards — showed that these successful dogs were using smell not sight. Her later studies confirmed this interpretation. It’s not just that dogs weight the olfactory evidence over the visual evidence. They really just can’t seem to use visual at all.

Bird tracks in snow. Image: Austris Augusts.

Time will tell, of course, whether a genius for tracking really is unique to our species. But even if another species is eventually found to tune in to visible tracks, that’s just the beginning. After all, one can read tracks in more or less sophisticated ways — a point several researchers have stressed. At its most basic, tracking involves inferring that some creature made the mark in front of me. But to a talented tracker, a set of prints may say much more. Not just that some animal was here — but a particular species of animal, of certain size, headed in a specific direction. Depending on their quality, prints may also hint at when the animal passed by, and whether it was idly browsing or high-tailing it.

One of the most detailed studies of such techniques is a slim book titled The Art of Tracking by Louis Liebenberg. It’s based on Liebenberg’s fieldwork with hunter-gatherers from the Kalahari, in Southern Africa. When engaging in the most sophisticated mode of track-reading — what Liebenberg calls “speculative tracking” — hunters make bold leaps of inference and imagination. From a peculiar pattern of paw prints, they may glean that two lions were playing. From the precise location of a set of tracks, they might hypothesize that an antelope was taking advantage of shade, and so likely passed through at a particular time.

The word “hypothesize” here is quite deliberate. Liebenberg argues that speculative tracking requires the same kinds of reasoning as, say, modern physics. Both ventures involve the close observation of data — data that is often vexingly incomplete. Both involve building models of the world to explain that data. And both involve gathering additional data to support or contravene those proposed models. Liebenberg’s argument is that tracking was, in a sense, the first science.

Could footprints really have loomed so large in the human saga? It may seem a bit of stretch. For today’s urbanites, footprints are little more than afterthought. Robert Macfarlane writes: “We easily forget that we are track-makers… because most of our journeys now occur on asphalt and concrete — and these substances are not easily impressed.” But this is not the case everywhere. Ethnographic reports from non-industrialized groups — particularly ones that don’t habitually wear shoes — suggest a much more prominent role for tracks. People in such communities readily distinguish the footprints of specific group members, for example. San children in the Kalahari reportedly recognize their mother’s footprints by the time they are four years old.

Whether or not we pay much attention to tracks these days, whether or not they played any role in human cognitive evolution, one thing is clear: they’ve left a deep imprint on the human imagination. They crisscross our myths and metaphors.

Several groups have concocted fantastical creatures with distinctive footprints. The Ciguapa of the Dominican Republic, the Curupira of Brazil, the Konderong of West Africa — all are mythical beings that, among other features, have backwards pointing feet. In the Amazonian language Xerénte, the word for the number two translates as ‘deer footprint’ and the word for three as ‘rhea footprint.’ The Bantu language Sesotho seizes on the fact that trackways capture an event unfolding in time. To express the idea that fall follows summer, a Sesotho speaker may say that fall “goes in summer’s footprints.”

An 1937 illustration of the Brazilian Curupira, one of several mythical beings that have backwards-facing feet, making them hard to track. Source: Wikipedia.

Tracks are also a recurring motif of visual culture. No doubt this is due to their arresting visual quality — etched and clean. Prints in fresh snow look like symbols on a blank page. According to Chinese legend, in fact, the first written characters were inspired by the sight of bird tracks. In the Boturini Codex, an Aztec manuscript dated tentatively to the16th century, footprints are used as a graphical device to connect episodes in the narrative, much like arrows are in Western contexts. Tracks also feature in ancient cave art: at different sites around the world, depictions of emu, marsupial, and reptile prints mingle with representations of human hands.

So what makes tracks so captivating to the eye and mind? Why have they attracted — why do they still attract — the attention of ichnologists and cognitive scientists, of hunters and artists? Part of the reason may be their double quality. They’re simple 2d images. But 2d images that can conjure 4d scenes, evoking bodies in motion. As a result, they can feel visceral, dynamic, even intimate.

A photo of Buzz Aldrin’s boot print on the moon, taken in July 1969. Image: NASA. Source: Wikipedia.

Another part of the appeal of tracks is that, again, they tell stories. Not just of bodies but of agents — of characters with goals and personalities. But it’s perhaps too swift to say that tracks simply tell stories, as though they address us clearly and declaratively. Better to say that tracks invite stories. Every set of tracks, after all, offers not one single narrative but a space of possible narratives. A trackway is less a clear plot than a kind of open-ended prompt.

And so it is that, 3.6 million years after the Laetoli tracks were tramped out in ash, scientists are still puzzling over their meanings. Just in the last decade a raft of new papers have offered new analyses of these same storied prints. And more and more ancient trackways keep coming to light. By analyzing them, we’re gleaning fresh insights into our ancestors — how they walked, how they lived, what their bodies were like.

And, of course, even as we continue to pore over these ancient tracks, fresh ones are being laid down. As Ralph Waldo Emerson once wrote, “Not a foot steps into the snow or along the ground, but prints, in characters more or less lasting, a map of its march.” And so it will continue, with all creatures stamping out stories in ash and mud, snow and dust, and some straining to read them.

– Kensy Cooperrider

Note: This post originally appeared in audio format on the ‘Many Minds’ podcast (@ManyMindsPod). You can listen to the episode here.

Our world is brimming with beings—human, animal, and artificial. We explore how they think, sense, feel, and learn. A project of @DivIntelligence & @kensycoop.