Fossil Footprints Offer Direct Evidence for Two Extinct Human Ancestors Sharing the Same Landscape

The Koobi Fora Research Project team, under the leadership of Louise Leakey, has conducted paleoanthrolological exploration and research at Lake Turkana in Kenya for decades.  

Leakey — a research professor in the Turkana Basin Institute — and members of the Koobi Fora team are co-authors of a new study published in Science with an international team of researchers from Kenya, the United States and the UK. It presents a newly discovered ~1.5-million-year-old fossil footprint site in northern Kenya, which records two different kinds of ancient human footprints, reflecting different patterns of anatomy and locomotion.

The paleontological record has often been insufficient to determine whether fossil human species actually lived together on the same landscapes at the same times. The researchers were able to distinguish the two different kinds of footprints using new methods that they recently developed for 3D analysis.

The fossil footprints were found in 2021, when Leakey, Cyprian Nyete, and other co-authors from the Koobi Fora Research Project and the Turkana Basin Institute were excavating unassociated hominin skeletal fossils from overlying sediments. Richard Loki was a member of that excavation team who recognized the first hominin footprint. Leakey then coordinated a team, led by Kevin Hatala — associate professor of biology at Chatham University in Pittsburgh — Roach, and Nyete, to excavate the footprint surface in July 2022.

“Fossil footprints provide us a clear picture of that instant in time, 1.5 million years ago,” said Leakey. “The different human ancestors may well have passed by each other, and observed the giant stork, ancient horses and hippos that also left their footprints along that shoreline that day.” 

The study of these footprints provides the first direct evidence of two different fossil human relatives, Homo erectus and Paranthropus boisei, occupying the same immediate landscape and likely interacting with each other. While skeletal fossils have long provided the primary evidence for studying human evolution, new data from fossil footprints are revealing fascinating details about the evolution of human anatomy and locomotion, and giving further clues about ancient human behaviors and environments.  

“Documenting the strata revealed that there are many more trackway surfaces that could be excavated nearby,” said Kay Behrensmeyer, a co-author from the Smithsonian’s National Museum of Natural History, who studied the paleoenvironmental context of the trackways. “These might hold more clues that could address questions about how different hominin species interacted, what they were doing wading in the shallow water.”

During this time and place in human evolution — about 1.5 million years ago in the Turkana Basin of Kenya — it has long been hypothesized that these fossil human species coexisted together. Homo erectus, a possible direct ancestor of ours, persisted for more than one million years after this. The other, Paranthropus boisei, went extinct within the next few hundred thousand years.

The research was supported by the National Geographic Society, U.S. National Science Foundation, the Turkana Basin Institute, and UK Research and Innovation.