A set of footprints found in the east African country of Tanzania from millions of years ago have long been thought to belong to a bear, but researchers have discovered they actually belonged to an ancient human species, suggesting there may have been more than one early human species existing at the same time.
The area of Laetoli in northern Tanzania is known for having fossils dating back millions of years. One site, Laetoli site G, is where the fossils of the Australopithecus afarensis have been recovered, widely regarded as one of the earliest human species walking on two legs. The famous skeleton of “Lucy” from 3.18 million years ago was part of the Australopithecus afarensis species.
However, not far from Laetoli site G, Laetoli site A had a set of footprints that appeared to be much wider than Australopithecus afarensis footprints. Because the footprints were not similar to any other known species of human, they were believed to belong in bear form.
Ellison McNutt was an assistant professor at Ohio University’s Heritage College of Osteopathic Medicine. She became interested in the mysterious prints as she wasn’t sure they were bear prints. McNutt’s interest is understanding the evolution of human walking and why it’s done on two legs.
McNutt went to a local bear sanctuary and had bears there make prints so she could compare them with the ones from Laetoli site A. These prints didn’t match.
“It’s not consistent with a bear, and it doesn’t appear to be consistent either with what we see in site G, which are the ones that belong to afarensis. According to McNutt, it appears to have a primitive foot.
The lead author of the peer-reviewed study published in the journal Nature on Wednesday explained what makes it appear to come from a hominin – the ancestors of humans – is because of the cross stepping the prints indicate. When bears or chimpanzees attempt to cross step, it would have to be on one leg. When they do so, they move in a waddle and can’t cross the step as gracefully as models on runways or people trying to keep their balance.
The hip muscles of hominins evolved to allow them to stand on both their feet and cross the steps. Steps also had impressions for a toe and a heel.
“That’s how we know for sure that, one way or another, this belongs to an individual within our lineage,” McNutt said.
McNutt led a group of international researchers who studied the prints. The prints proved to be wider than site A’s, but they were most likely made by a juvenile hominin. Full grown humans are smaller than most people today.
The team doesn’t know when the prints were created, unlike Lucy. However, analysis revealed that it was made around a thousand years ago. What they find remarkable is that time frame overlaps with when the Australopithecus afarensis were also roaming around.
“It’s very possible that the individual who made Laetoli A could have kind of looked up across the landscape and seen an Australopithecus afarensis walking by,” McNutt said. It tells us we were not alone in our past and that our family tree was more complete and diverse. “There wasn’t one right way to be human.
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Jeremy DeSilva (senior author, associate professor in anthropology, Dartmouth College) said there remain many questions regarding how humans started to walk on two feet. Furthermore, the discoveries only complicate its evolution since there were two hominins.
McNutt stated that they hope to discover more of these prints so we can better understand how and why they move.
Taylor Avery from USA TODAY, Contributing
Follow Jordan Mendoza Twitter @jordan_mendoza5.