Ancient Fossil Footsteps Found in Kenya May Hint That an Early Human Relative Was Larger Than Previously Thought

Newly documented fossil footprints in Kenya are offering a rare, ground-level view of early human relatives and raising the possibility that one of them was bigger than scientists had assumed. The trackway, described in a new study in the Proceedings of the National Academy of Sciences, preserves evidence from at least seven hominins. Rather than presenting a single isolated step, the find records several individuals in the same landscape and opens fresh questions about their bodies, movement and social lives.

The discovery began during work at a surface that also held hippo impressions. Excavator Kimolo Mulwa was removing the layers of rock around those animal tracks when he encountered something unexpected: two fossilized prints made by an ancient human relative. Such sites can preserve many kinds of marks across an extensive exposed surface, so the find emerged from work already focused on reading a broader scene rather than from a search for one particular footprint.

When Behrensmeyer came to see the excavation, Mulwa’s reaction signaled that the work had taken an unusual turn. The two prints were compelling, but they were not immediately the project’s central task. With other field priorities underway, the researchers protected the newly exposed impressions by covering them again, leaving a fuller investigation for a later return.

That return unfolded in stages. Teams revisited the Kenyan location in 2016 and again in 2023, reopening the area and extending the search. The first efforts to enlarge the excavated surface did not yield more hominin steps. Eventually, however, the evidence grew from the original pair of prints into a track assemblage that researchers say represents no fewer than seven individuals.

The accumulation matters because footprints preserve behavior differently from bones or individual artifacts. A skeleton can indicate the physical traits of one animal or person, while a trackway can show that multiple beings used the same patch of ground. Here, the prints provide a momentary record of hominins sharing an environment that also retained signs of other animals. The study therefore speaks not only to anatomy, but to how early relatives of humans navigated their surroundings.

Kevin Hatala, a biology associate professor at Chatham University and the study’s lead author, said the pattern is consistent with a basic expectation about hominin life: they were not generally solitary. He noted that one hominin footprint often points researchers toward others nearby. The Kenyan tracks do not on their own reconstruct the relationships among the individuals, but their concentration makes a social setting more plausible than an encounter involving only one traveler.

The size implication is especially intriguing. The newly reported steps may indicate that the early human relative responsible for some of the tracks was larger than earlier estimates suggested. Footprints can offer clues through their dimensions and form, but they are not a complete substitute for a body. The conclusion should therefore be read as an opening for further comparison, rather than a final account of the species’ size or the identity of every track maker.

There is also a practical lesson in the history of the excavation. Important evidence was initially recognized amid hippo tracks, then deliberately reburied until the team could devote the necessary time and resources to it. That sequence underlines why fossil fieldwork often advances through repeated visits: an exposed surface may reveal more information only after careful expansion, documentation and comparison with nearby impressions.

Next work will likely focus on separating what the trackway can demonstrate directly from what it can only suggest. Researchers can examine how the individual prints relate to one another, compare them with other hominin evidence, and consider the setting in which the people moved. Even with those limits, the Kenyan surface has added an unusually social dimension to the fossil record: it captures several early human relatives in one place, leaving traces of a shared passage through an ancient world.

Source: Smithsonian Magazine