1.4-Million-Year-Old Footprints Reveal a Surprisingly Large Human Relative

A set of 1.4-million-year-old fossil footprints from northern Kenya is giving scientists a rare look at how an extinct human relative, Paranthropus boisei, may have moved and interacted. The tracks were found near an ancient lakeshore close to Lake Turkana.

The prints appear to record eight Paranthropus boisei individuals in the same place at roughly the same time. Researchers call the find a snapshot of "fossil behavior," because unlike bones, which can accumulate over long periods, footprints capture a single brief moment.

The international team, made up of researchers from the US and Kenya, used analytical techniques it first developed in 2024 to identify the tracks as Paranthropus boisei, based on foot anatomy and the way the individuals appear to have moved.

The size of the footprints surprised the researchers. "The sizes of the footprints indicate human-like body sizes - up to 1.8 meters tall and around 75 kilograms," said lead author Kevin Hatala of Chatham University, who is also an associated researcher at the Max Planck Institute for Evolutionary Anthropology in Leipzig. For decades, most known Paranthropus boisei fossils have been skulls with large jaws and teeth. The new tracks challenge earlier estimates that the species was much smaller than Homo erectus, another hominin that lived at the same time.

The eight individuals appear to have traveled together, and researchers found no obvious evidence of females or children among them. Co-author Neil Roach of Harvard University said the group hints at a complex social structure, in which males may have competed for mates but also tolerated each other for safety.

The discovery is part of a larger collection of hominin footprints found in ancient lakeshore environments around Lake Turkana. Researchers have documented hundreds of hominin footprints at more than half a dozen sites in the region.

Co-author Kay Behrensmeyer of the Smithsonian Institution said the team hopes to understand what geological conditions allowed the tracks to survive, which could also explain why hominins kept returning to the lakeshore for more than 100,000 years. The research team plans to return to Kenya this year to continue investigating the footprint sites.