Washington (AFP) – Take a second look at the prehistoric footprints that have baffled scientists since the 1970s: were they left by extinct animals or human ancestors?

When famed paleontologist Mary Leakey discovered footprints in Tanzania 40 years ago, the evidence was murky.

Instead, Leakey focused his attention on other fossil footprints that may be more clearly related to early humans. who – which FootprintsIt was found at a site called Laetoli G, and is the first clear evidence that early humans walked upright.

Decades later, a new team has re-excavated the confounding footprints, found at a site called Laetoli A, and made the images and 3D scans available for other researchers to continue the discussion.

The research was published on Wednesday in the journal. nature of mood.

“These footprints have been in the mystery category for 40 years,” said Rick Potts, director of the Human Origins Project at the Smithsonian Institution.

“It’s a really exciting idea to be researched and studied again,” added Potts, who was not involved in the research.

What has long puzzled scientists is that these footprints – large, arrogant fifth-toe footprints, estimated to be around 3.7 million years old – don’t closely match anything scientists identified elsewhere.

“They didn’t have the right weight and foot movement that would be easily recognizable as humans, so other explanations have been sought,” said co-author and paleontologist Jeremy DeSilva, including that it may belong to an extinct species of bear.

He and other researchers returned to the site in 2019 and used Leakey’s original maps to identify the mysterious prints, preserved in a layer of volcanic ash that has cooled and solidified.

Ohio State University co-author Ellison McNutt studied the mechanics of the feet of young black bears at the New Hampshire Wildlife Rescue Center to see if a small bear walking on its hind legs could leave similar footprints.

She was carrying a tray of apple puree to entice the chicks to walk towards her. Each step was recorded in the folder path for analysis.

She said that bears that walk upright put their weight on their heels first, like humans. “But the proportions of the foot are not the same.” He concluded that the fossils’ footprints were not left by the bears.

Other factors, such as the spacing of the footprints, led the study authors to conclude that these footprints were left by species hitherto unknown to early human ancestors.

Not everyone is convinced.

This fluctuated between an ancient bear or an ancient human, said Potts of the Smithsonian, adding that an ancient bear may have walked differently than a modern black bear.

William Harcourt Smith, a paleoanthropologist at the American Museum of Natural History who was not involved in the research, said he was convinced it wasn’t a bear but wasn’t sure it was a Neanderthal.

“These footprints still belong to some form of non-human ape,” he said.

If two different species walk upright in the landscape at the same time, this indicates different simultaneous experiences of walking on two legs – complicating the traditional view of human evolution as strictly linear.

“It’s cool to think of,” Harcourt Smith said.

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