A set of 1.4 million-year-old footprints indicates that one of our extinct evolutionary ancestors was larger and more social than we thought. The footprints belonging to a long-dead hominid called Paranthropus boisei were found preserved on the shore of a lake in northern Kenya and are described in a study published today in the Proceedings of the National Academy of Sciences.

Neanderthals (Homo neanderthalensis) and homo erectus They are some of the best-known archaic humans, but they are far from the only examples. Dozens of other hominids are documented around the world, including more obscure variants such as the strong-jawed. Paranthropus boisei. Much of the anatomical information on boisei It has been obtained from a handful of skulls and teeth, leaving details on general size and physiology vague. They were once thought to be less developed than other members of the family tree, but researchers now understand that boisei He was probably advanced enough to wield tools with the strength of a gorilla.

Some of the most valuable knowledge about boisei It doesn’t come from body parts, but from the traces they left behind. In 1978, a team led by Smithsonian National Museum of Natural History paleontologist Kay Behrensmeyer discovered boisei Footprints along Lake Turkana in northern Kenya. Behrensmeyer returned several times over the years to the site known as GaJi10, discovering more traces of boiseias well as ancient antelopes, hippos and other large animals. In total, the researchers inventoried 21 footprints left by eight hominids dating back to the Early Pleistocene, approximately 1.43 million years ago. Meanwhile, a nearby separate road yielded footprints of both boisei and H. erectusproving that the two hominid species shared the same habitat for hundreds of thousands of years.

“We can’t say how the two different hominids interacted in the mudflats, but we know they were both here at the time,” Behrensmeyer said in a statement.

Experts long believed boisei be stockier than relatives like H. erectusbut these footprints tell a different story. Based on gait patterns and anatomical measurements, it now appears boisei It was relatively the same size as its hominid companions.

“The sizes of the footprints indicate similar body sizes to humans: up to 6 feet tall and about 165 pounds,” explained Kevin Hatala, an evolutionary anthropologist at Chatham University in Pennsylvania and co-author of the study.

The distribution and dating of the footprints also suggest that archaic humans sometimes traveled in groups. In one case in GaJi10, eight men, mostly adults, P. boisei We walked together near Lake Turkana without children or women. This implies a much more complex social structure, in which males frequently competed for mates, but also collaborated in times of need.

“What’s special about footprints from a scientific point of view is that they preserve a moment in time,” says Behrensmeyer. “They also allow people to relate to these fossils much more easily than to an isolated piece of bone or jaw.”

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