The strange walk of an early human

By Victoria Jaggard, SCIENCE executive editor

One of the strangest changes for me during the pandemic has been life without high heels. We don’t wear shoes in the house, so I’ve been padding around in bare feet or socks for almost two years now. That would amaze most folks I know, who are used to seeing me in four-inch platforms. I’ve hiked through jungles, climbed volcanic plateaus, and crossed the Washington, D.C., Mall multiple times in my favorite vertiginous footwear. I can only imagine this proclivity has given me an odd gait—and that may put me in the company of a mysterious ancient relative.

Scientists recently took a closer look at a set of tracks in Tanzania (pictured above) that are near some of the most famous known to paleontologists: 3.6-million-year-old footprints left behind by the early human relative Australopithacus afarensis. As Maya Wei-Haas reports, these prints represent the first clear evidence of our ancestors walking on two feet.

The scientists who found them in the 1970s also stumbled across five more prints by a biped that was crossing one foot over the other as it shambled through the mud. It won’t exactly make the Ministry of Silly Walks, but it is pretty darn odd for the time period. "The extreme version of this would be like model walking," says study leader Ellie McNutt of Ohio University.

For a long time scientists wrote off the unusual prints thinking they’d been created by a bear walking on its hind legs. But McNutt and her colleagues know their bears, and they raised an eyebrow. Combining video analysis of bears walking with advanced scans of the prints and measurements from other hominin trackways, they conclude that ursine interlopers are off the hook. Instead, they say, the prints may belong to a mysterious human relative that crossed paths with A. afarensis way back when.

Other scientists are intrigued if not entirely convinced. It’s hard enough to define a new species based on its fossil remains, let alone a few footprints. More study and analysis could yield further clues to cement their conclusions, and the team does plan to go back to the site to search for more prints—but they better act fast. These kinds of fossil trackways are at constant risk of erosion, and preserving them is notoriously tough.

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