Footprints show two extinct human ancestor species lived together

Water brings life together. The shores transform into busy corridors where birds, ungulate mammals and different species of human ancestors, or hominins, meet.

At Lake Turkana in northern Kenya, about 1.5 million years ago, a short window of wet silt captured this traffic with unusual clarity.

Scientists studied these impressions and discovered a precise, almost real-time recording of who walked there and how they moved.

Geology sets the scene to a narrow slice of time. A footprint layer lies a few meters beneath a bed of volcanic ash dating to about 1.52 million years ago.

The imprints formed and were quickly buried by fresh sediment, congealing into delicate shapes before water or wind could erase them.

Thin alternating beds of fine sand and silt mark a shallow shoreline that has preserved what would normally have disappeared within a few hours.

A surface layer, labeled TS-2, records several hominid footprints alongside the footprints of large waders, bovid hoof marks, and the footprints of horse-like animals.

Because the surface was covered and then covered in a matter of hours or days, it shows neighbors sharing the same lake margin, not just species spread out over centuries.

The researchers mapped a continuous trail of hominid footprints from one individual and three isolated hominid footprints likely made by three others.

Around them, dozens of traces of birds, cattle and equines fill the slab. The mud was firm at the top and softer a few inches below, which explains the clear toe marks and light heels. The bedding above indicates gentle and rapid burial by fine sands.

“In biological anthropology, we are always interested in finding new ways to extract behavior from the fossil record, and this is a great example,” explained Rebecca Ferrell, a program director at the National Science Foundation who helped fund this part of the research.

“The team used cutting-edge 3D imaging technologies to create a completely new way to look at footprints, which helps us understand human evolution and the roles of cooperation and competition in shaping our evolutionary journey.”

Footprints record kinematics – the mechanics of how a foot presses, slides and lifts. On early Pleistocene surfaces in the Koobi Fora region, the team found two recurring gait patterns side by side.

They appear on the same surfaces and are repeated on neighboring sites of the same age. This repetition indicates that more than one type of hominid used the shoreline at the same time.

After comparing shapes, depths and pressure patterns, the study interprets these signature pairs as two species already known in the region: Homo erectus And Paranthropus boisei.

“Their presence on the same surface, close together in time, places the two species at the edge of the lake, using the same habitat,” said Craig Feibel, study author and professor in the Department of Earth and Planetary Sciences and the Department of Anthropology at the Rutgers School of Arts and Sciences.

Homo erectus he probably walked with a more modern gait adapted to the distance. Paranthropus boiseiwith its robust chewing anatomy, may have moved differently – still upright, but not tuned for long, steady travel in the same way.

Importance of “fossil traces”

Feibel called the footprints important because they fall into the category of “trace fossils” — a group that can include footprints, nests and burrows.

Unlike body fossils such as bones and teeth, which record past life but can be moved by water or predators, trace fossils capture behavior in place. Feibel added that fossil tracks cannot be moved.

“This proves beyond a doubt that not just one, but two different hominids walked on the same surface, literally hours apart,” Feibel noted.

“The idea that they lived simultaneously is perhaps not a surprise. But this is the first time it’s been demonstrated. I think it’s really huge.”

Share space without mixing roles

This evidence takes “coexistence” from a vague idea to something you can see beneath your feet. Bones from the same rocky limbs may show broadly overlapping hominid species.

These tracks reduce overlap to the same coastline, during the same day or season.

This level of detail opens the door to ecological questions: how species met in the water, how they avoided conflict, and whether they divided resources by separating niches.

The margins of lakes concentrate food, shade and security. They also increase competition. When many species converge, even small differences in gait, endurance and food choices can tip the scales.

If Homo erectus covered the ground more effectively, it could have been further between the water and the food. If Paranthropus boisei favored different foods or microhabitats, this could reduce direct competition while using the same shoreline.

“Fossil footprints are exciting because they provide vivid snapshots that bring our fossil relatives to life,” explained Kevin Hatala, first author of the study and associate professor of biology at Chatham University in Pittsburgh, Pennsylvania, who has studied hominid footprints since 2012.

“With this type of data, we can see how living individuals millions of years ago moved through their environments and potentially interacted with each other, or even other animals. That’s something we can’t really get from bones or stone tools.”

Confidence level and limits

Footprints rarely identify species by size alone. Different hominids could leave similarly sized prints.

What strengthens this thesis is the consistent pairing of two movement signatures across multiple sites, combined with the known fossil record for the region and time.

The prints do not show faces, but reveal how bodies moved, which may be equally informative in determining who shared the landscape.

Sediments and ashes also reduce uncertainties. Volcanic layers act as timestamps. Once you date the ashes, you can limit the age of the traces underneath.

Here, the nearly 1.52 million year old ash provides that anchor, keeping the surface of the footprint almost 1.5 million years old.

This work highlights locomotion as a common thread in human history. Success didn’t just depend on tools or diets.

It also relied on how efficiently the ancestors moved from water to food to refuge, and how they managed to live near close cousins ​​without constant conflict.

Movement shapes encounter rates, territory size, and access to resources. In a coastal environment that has many needs in one place, the mechanics of each step matter.

A rare, clear and exciting scene

On the fullest surface, a continuous hominid track and three isolated footprints are found among numerous bird, bovid and equine tracks.

The firmness of the mud near the top and the softness just below produced sharp details, and rapid burial preserved them for more than a million years.

Most prints disappear quickly. These have survived long enough to change what we can say about who stood where – and when.

Two branches of our family hiked the same lakeshore at almost the same time. Their footsteps bear different movement signatures, hinting at distinct strategies for moving and coping.

Through geological precision and careful measurements, the study turns a general idea – overlap in place and time – into a specific scene: early humans sharing a shoreline, leaving different styles of walks on the same soft ground.

The full study was published in the journal Science.

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