Toothy human ancestor may have traveled in all-male packs

One of the larger hominin footprints with a 6” ruler for scale. The tracks were made in soft mud and then filled in with sand by gentle shoreline currents, preserving the impressions. Credit: Kay Behrensmeyer / Smithsonian Get the Popular Science daily newsletter💡 Breakthroughs, discoveries, and DIY tips sent six days a week. By signing up, you confirm you are 16+, will receive newsletters and promotional content and agree to our Terms of Use and acknowledge the data practices in our Privacy Policy. You may unsubscribe at any time. A set of 1.4 million year old footprints indicate that one of our extinct evolutionary ancestors was both larger and more social than we thought. The footprints belonging to a long-deceased hominin called Paranthropus boisei were found preserved on a lakeshore 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 are some of the most well-known archaic humans, but they are far from the only examples. Dozens of other hominins are documented around the world, including more obscure variants like strong-jawed Paranthropus boisei. Much of the anatomical information about P. boisei has been gleaned from a handful of skulls and teeth, leaving vague details about overall size and physiology. Once thought less-developed than other members in the family tree, researchers now understand that P. boisei was likely advanced enough to wield tools with a gorilla-strength grip. Overview of the excavated track surface with a mix of deeper hippopotamus and antelope footprints and shallower hominin tracks visible. Credit: Kay Behrensmeyer / Smithsonian Some of the most invaluable knowledge about P. boisei comes not from body parts, but the imprints they left behind. In 1978, a team led by Smithsonian National Museum of Natural History paleontologist Kay Behrensmeyer discovered preserved P. boisei footprints along Lake Turkana in northern Kenya. Behrensmeyer returned multiple times over the years to the site known as GaJi10, uncovering more tracks from P. boisei, as well as ancient antelope, hippopotamuses, and other large animals. In total, researchers inventoried 21 footprints left by eight hominin individuals dating back to the Early Pleistocene about 1.43 million years ago. Meanwhile, a separate nearby pathway yielded tracks from both P. boisei and H. erectus, proving that the two hominin species shared the same habitat for hundreds of thousands of years. “We can’t say how the two different hominins interacted on the mudflats, but we know they were both here at this time,” Behrensmeyer said in a statement. Experts long believed P. boisei to be stockier than relatives like H. erectus, but these footprints tell a different story. Based on gait patterns and anatomical measurements, it now seems P. boisei was relatively the same size as its fellow hominin. “The sizes of the footprints indicate human-like body sizes—up to 6 feet tall and around 165 pounds,” explained Kevin Hatala, an evolutionary anthropologist at Chatham University in Pennsylvania and a study co-author. The imprints’ distribution and dating also suggest the archaic humans sometimes traveled in groups. In one instance at GaJi10, eight mostly adult male P. boisei walked together near Lake Turkana without children or females. This implies a much more complex social structure—one with males that frequently competed for mates, but also collaborated in times of need. “The special thing about footprints scientifically is that they preserve an instant in time,” said Behrensmeyer. “They also allow people to relate to these fossils much more easily than an isolated piece of bone or jaw.” 2026 Popular Science Home of the Future Awards 39 products that will improve your everyday life.