Archaeologists Found 120,000-Year-Old Human Footprints Where They Shouldn’t Be

4 min readBetween roughly 112,000 and 121,000 years ago, a handful of people walked along the muddy shore of a lake in what is now Saudi Arabia’s Nefud Desert. Elephants and camels had churned up the ground, and the humans left seven footprints among hundreds of animal tracks before sediment sealed the whole scene for eternity. When researchers described the site, called Alathar (Arabic for “the trace”), in a 2020 paper in Science Advances, we called the prints “the oldest-ever human footprints on the Arabian Peninsula” and marveled that they had survived at all. As the researchers noted, an experimental study of modern footprints in mud flats “found that fine details were lost within two days and prints were rendered unrecognizable within four.”Six years later, the original interpretation still holds. “The age estimate remains about 120,000 years ago based on scientific dating,” Michael Petraglia, an archaeologist at Griffith University in Australia who studies human evolution and dispersal, tells Popular Mechanics. “The size and shape of the footprints are consistent with Homo sapiens.” What has changed is the record around them. Petraglia says sites dated since 2020 suggest that people entered Arabia when wetter weather filled the peninsula with lakes. During these “Green Arabia” periods, people could find drinking water in places that are now desert. When the water disappeared, some of those populations may have disappeared with it, possibly including the people who left the Alathar tracks.The desert kept opening and closingArabia went through this cycle many times. For a 2021 study in Nature, Huw Groucutt, Petraglia, and their colleagues dated ancient lake deposits in the Nefud that contained stone tools and animal fossils. They found that human ancestors moved into the Arabian interior at least five times between about 400,000 and 55,000 years ago, each time during a wetter spell, and each phase had its own style of stone tools. “This looks like different populations, and indeed species, moving into the area at different times,” says Groucutt, an archaeologist and senior lecturer at the University of Malta who studies human prehistory and environmental change. Once the rains stopped, he says, there probably wasn’t enough water for anyone to stay.Even in the good years, people probably kept moving. Groucutt pictures groups traveling among scattered small lakes and other water sources in a landscape that was still highly seasonal, with very hot summers. Alathar fits that picture. The researchers found no stone tools or butchered bones at the site and concluded that the lake “was only briefly visited by people,” most likely for drinking water. For Petraglia, that brevity is what makes the tracks valuable. “Footprints capture a moment in time, illustrating that people walked along lakeshores at the same time as animals,” he says.These walkers may have no living descendantsIf the Alathar walkers were Homo sapiens, Groucutt thinks they belonged to a branch of humanity that didn’t make it. “The dominant view from genetics is that people living outside Africa today descend from people spreading into Asia around 50 to 80,000 years ago, so earlier people died out,” he says. By that reasoning, the footprints are “probably an example of an earlier, failed, migration.” That kind of failed migration is also known from other sites, including Skhul Cave on Mount Carmel, where fossils of early Homo sapiens were found. Reaching Arabia, then, came with no guarantee of surviving there. The people who left these tracks may have died out, and a much later migration brought the ancestors of most people living outside Africa today. Petraglia describes the same pattern of shifting fortunes: “Migrations were repeated movements, with groups expanding, contracting, and possibly disappearing from parts of the peninsula as conditions changed.”The green windows may have been trapsAs Arabia dried, Groucutt thinks, people may have retreated south, following the water into the wetter parts of the peninsula. Differences in stone tools suggest that these southern populations developed their own ways of doing things as they lost contact with people farther north. But the south eventually dried up too. Groucutt reads gaps in the archaeological record as a sign that the remaining groups became too small and isolated to make it through the worst dry spells. The same lakes that drew people into Arabia could leave them stranded, crowded around whatever water remained and with fewer and fewer places to go. The Alathar tracks date to a dry spell during the last interglacial, which puts their makers in exactly this kind of shrinking landscape.The proof is hard to find in a hot desertSettling the question will take evidence that a desert doesn’t give up easily. Groucutt would welcome hominin fossils, though he doubts they would be the “smoking gun” people sometimes imagine, since bones can be hard to date and hard to assign to a species. Ancient DNA could do more, but in low latitudes it “just doesn’t go that far back,” he says, because “hot places are bad for preservation.” Petraglia is hunting for something more specific. “A securely dated human fossil or a long, stratified sequence showing human occupations across both wet and dry periods would be transformative,” he says. Working with Saudi colleagues who help choose sites and reach them, his team is searching around former water sources for evidence of people who stayed as the climate changed.Until that evidence turns up, the Alathar footprints remain one of the few direct records of these early travelers. If they left no descendants, the site’s name may best describe what survives of them: a trace.Eric Spitznagel is a frequent contributor to magazines like Playboy, Esquire, and the New York Times, and was employed for over two decades by the Second City comedy theater, where Stephen Colbert was his Secret Santa _twice.