TWO sets of 1.5million-year-old footprints belonging to separate species of ancient humans have been discovered on the same lakeshore.
It had long been hypothesised that these ancient human species coexisted, but researchers now say there is “hard proof”.
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The tracks, found on Lake Turkana in Kenya, belong to the species Homo erectus and Paranthropus boisei, according to researchers.
These were the two most common living human species of the Pleistocene Epoch.
If these human ancestors didn’t cross paths, they almost certainly walked the shore within hours of each other, said Craig Feibel, a professor in the Rutgers School of Arts and Sciences.
Fossil records suggest these hominins (the term for all animals considered to be within the human lineage) coexisted for roughly 3million years.
However, the Paranthropus boisei eventually went extinct and were outlived by the Homo erectus, whose existence persisted for another 1million years.
Both species walked upright with two feet, and were highly agile.
“Their presence on the same surface, made closely together in time, places the two species at the lake margin, using the same habitat,” added Feibel, who is also an author of the study.
Feibel added: “This proves beyond any question that not only one, but two different hominins were walking on the same surface, literally within hours of each other.
“The idea that they lived contemporaneously may not be a surprise. But this is the first time demonstrating it. I think that’s really huge.”
Little is known about how these species coexisted – whether it was violent or collaborative.
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Homo erectus may have bred with the early human species’ it encountered, or they could have feared them.
Scientists are unsure why the Homo erectus survived another 1million years, and the Paranthropus boisei did not.
Skeletal fossils are the main source for studying human evolution.
But they fail to offer glimpses into ancient human behaviours and environments, according to Kevin Hatala, the study’s first author.
“Fossil footprints are exciting because they provide vivid snapshots that bring our fossil relatives to life,” said Hatala, an associate professor of biology at Chatham University in Pittsburgh, who has been investigating hominin footprints for over a decade.
“With these kinds of data, we can see how living individuals, millions of years ago, were moving around their environments and potentially interacting with each other, or even with other animals.
“That’s something that we can’t really get from bones or stone tools.”
Fossil footprints, which fall under a category known as “trace fossils”, also cannot be moved, noted Feibel, who says this offers researchers a more accurate glimpse into the lives of ancient humans.
Researchers discovered the footprints in 2021 when fossil bones were found at the Lake Turkana site during a dig organised by paleontologist Louise Leakey.
The field team, led by Cyprian Nyete, noticed fossils on the surface and were excavating to try and find the source.
While digging out the fossils on the top layer of a bed, Richard Loki, one of the excavators, noticed some giant bird tracks.
He then spotted the first hominin footprint, which was enough for Leakey to coordinate a team to excavate the footprint surface in July 2022.
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