A pair of footprints discovered in Tanzania in 1980 could rewrite the history of human evolution. The footprints, which are 3.66 million years old, were initially believed to be made by a young bear that was walking upright on its two hind legs.
The fossilized footprints were brushed off at the time, but a team of researchers from Dartmouth University went back to the site in 2019 and began re-examining the footprints.
They compared the footprints to other animals, including American black bears and chimpanzees, and determined they likely belonged to "a small, cross-stepping bipedal hominin."
The footprints are distinct from another set left by an early human ancestor classified as Australopithecus afarensis, the researchers explained in a study published in the journal Nature. Jeremy DeSilva, who was a co-author of the study, said that the findings suggest that two distinct species of human ancestors were living in the same area at the same time.
"These footprints demonstrate that the evolution of upright walking was more complicated and more interesting than we previously thought," DeSilva said, according to CNN. "There were at least two hominins, walking in different ways, on differently shaped feet, at this time in our evolutionary history, showing that the acquisition of human-like walking was less linear than many imagine."