WASHINGTON app Muddy footprints left on a Kenyan lakeside suggest two of our early human ancestors were nearby neighbors some 1.5 million years ago.
The footprints were left in the mud by two different species appwithin a matter of hours, or at most days,app said paleontologist Louise Leakey, co-author of the research published Thursday in the journal Science.
Scientists previously knew from fossil remains that these two extinct branches of the human evolutionary tree app called Homo erectus and Paranthropus boisei app lived about the same time in the Turkana Basin.
But dating fossils is not exact. appItapps plus or minus a few thousand years,app said paleontologist William Harcourt-Smith of Lehman College and the American Museum of Natural History in New York, who was not involved in the study.
Yet with fossil footprints, appthereapps an actual moment in time preserved,app he said. appItapps an amazing discovery.app
The tracks of fossil footprints were uncovered in 2021 in what is today Koobi Fora, Kenya, said Leaky, who is based at New Yorkapps Stony Brook University.
Whether the two individuals passed by the eastern side of Lake Turkana at the same time app or a day or two apart app they likely knew of each otherapps existence, said study co-author Kevin Hatala, a paleoanthropologist at Chatham University in Pittsburgh.
appThey probably saw each other, probably knew each other was there and probably influenced each other in some way,app he said.
Scientists were able to distinguish between the two species because of the shape of the footprints, which holds clues to the anatomy of the foot and how itapps being used.
H. erectus appeared to be walking similar to how modern humans walk app striking the ground heel first, then rolling weight over the ball of the foot and toes and pushing off again.
The other species, which was also walking upright, was moving appin a different way from anything else weappve seen before, anywhere else,app said co-author Erin Marie Williams-Hatala, a human evolutionary anatomist at Chatham.
Among other details, the footprints suggest more mobility in their big toe, compared to H. erectus or modern humans, Hatala said.
Our common primate ancestors probably had hands and feet adapted for grasping branches, but over time the feet of human ancestors evolved to enable walking upright, researchers say.
The new study adds to a growing body of research that implies this transformation to bipedalism app walking on two feet app didnappt happen at a single moment, in a single way.
Rather, there might have been a variety of ways that early humans learned to walk, run, stumble and slide on prehistoric muddy slopes.
appIt turns out, there are different gait mechanics app different ways of being bipedal,app Harcourt-Smith said.
