A group of fossil footprints found beside an ancient lake in northern Kenya is giving researchers one of the clearest records of early human behavior ever found. The tracks date to about 1.43 million years ago and capture a single moment when at least eight hominins walked across wet ground before the surface hardened.
One of the large, 1.4-million-year-old footprints that the team excavated. A 6-inch (~15 cm) ruler is shown for scale. Credit: Kay Behrensmeyer
The footprints were uncovered in the Koobi Fora Formation near Lake Turkana. Based on the shape of the feet and the way the individuals walked, researchers think the track makers were most likely Paranthropus boisei, an extinct human relative. Fossil bones from this species are mostly skulls and teeth, so very little is known about the rest of the body.
Footprints offer something fossils rarely preserve. They record movement as it happened. They show how many individuals were present, where they walked, and how they moved across the landscape. The newly found tracks point to a group made up mostly of adult males traveling together along the lakeshore.
The size of the footprints came as a surprise. Earlier studies based on fossil bones suggested Paranthropus boisei was much smaller than Homo erectus, another human relative living in East Africa at the same time. The new evidence tells a different story. Some track makers appear to have stood close to 1.8 meters, or about 5 feet 11 inches, tall and weighed around 75 kilograms, or 165 pounds. Those figures match estimates for Homo erectus much more closely than expected.
This leaves researchers with two possible answers. The footprints belong to Paranthropus boisei, which means the species reached much larger body sizes than fossil bones suggest. The other option is that the tracks came from Homo erectus. If so, members of this species showed far more variety in foot shape and walking style than researchers thought.
The footprints still resemble others linked to Paranthropus boisei. Their foot shape and pattern of movement differ from modern humans and look closer to earlier Australopithecus species. For this reason, the team favors Paranthropus boisei as the track maker, although the question is still open.
Kevin Hatala and colleagues discuss the ancient footprints excavated in northern Kenya in 2023. Credit: Kay Behrensmeyer
The tracks also offer rare evidence of social behavior. Several large adults appear to have walked together across the lakeshore. Researchers think the group included multiple adult males. Such evidence is rarely preserved in the fossil record because bones usually tell little about how individuals interacted during life.
The site adds to a growing collection of fossil footprints from the East Turkana region. Researchers have now recorded hundreds of hominin tracks from several nearby locations. Some sites lie about 40 kilometers, or 25 miles, apart and formed at roughly the same time. Together they show early human relatives returned to these lake margins for more than 100,000 years, likely because the area offered fresh water and food.
Researchers plan more fieldwork in Kenya to uncover additional footprint surfaces. Every new track adds another piece to the story of how early human relatives moved, lived together, and shared the same landscape long before modern humans appeared.
Publication: Hatala, K. G., Roach, N. T., Harris, J. W. K., Kiura, P., Ndiema, E. K., Sila, B., … Behrensmeyer, A. K. (2026). Insights into hominin body size, locomotion, and behavior from Early Pleistocene trackways in northern Kenya. Proceedings of the National Academy of Sciences of the United States of America, 123(31). doi:10.1073/pnas.2530996123