Researchers reported 21 fossil footprints made by at least eight hominins beside an ancient lake in northern Kenya about 1.43 million years ago. The Max Planck Institute for Evolutionary Anthropology said the tracks place eight individuals at the same site and time, with all thought to be adults.

The study, published July 27 in the Proceedings of the National Academy of Sciences, links the tracks most strongly to Paranthropus boisei. The footprints also yield body-size estimates larger than the sparse skeletal record had suggested, while leaving uncertainty over which hominin species made them.

Twenty-one tracks preserve a brief lakeshore crossing

The GaJi10 track surface lies in the Koobi Fora Formation near Lake Turkana. The site was first excavated in 1978, then expanded in 2016 and 2023 after researchers removed sand that had protected the original surface.

The Smithsonian Institution's account says volcanic ash in surrounding rock dated the surface to about 1.43 million years ago and that it contains 21 hominin footprints alongside tracks from hippos, antelope and other animals. The hominin prints represent at least eight individuals.

Fossil impressions exposed in sandy sediment at an excavation site (illustrative image)

Foot mechanics favor Paranthropus, but size complicates the attribution

The researchers compared the tracks' anatomy and movement patterns with footprints associated with P. boisei and Homo erectus, the two hominins known from the region at that time. The flatter arches and more mobile big toes resemble the pattern previously assigned to Paranthropus.

The largest footprints produced estimates of about 1.8 meters in height and 75 kilograms in mass. Those values approach estimates for H. erectus and exceed most skeletal estimates for P. boisei. The analysis therefore favors P. boisei on foot mechanics while acknowledging that unusually variable H. erectus anatomy could also explain the tracks.

Tracks suggest coordinated movement, not a settled social structure

Most of the footprints run in the same direction and appear to have been made within a short interval. The researchers classified several individuals as probable adult males and proposed that they crossed the lakeshore together.

That interpretation does not show that P. boisei routinely traveled in male-only groups. Age and sex were inferred from track dimensions, no skeletons were found with the prints, and a single preserved crossing cannot establish a species-wide social pattern.

Earlier tracks show two hominin species used the same habitat

A separate 2024 study examined a slightly older footprint surface in the same part of northern Kenya. The peer-reviewed study reported two distinct walking patterns attributed to H. erectus and P. boisei, placing both species in the same immediate lakeshore setting about 1.5 million years ago.

The GaJi10 analysis adds evidence about body size and movement but does not reveal how the two species interacted. Together, the sites show that footprints can preserve short episodes of behavior that bones and teeth alone do not record.