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Over a million million years ago, two different types of early humans crossed paths on the beach, perhaps locking eyes. These early forerunners of Homo sapiens wandered through an area full of wild animals, including giant anteaters that were two meters (6.5 feet) tall.
The surprising discovery of fossilized footprints pressed into the soft mud preserved an unexpected and surprising moment, showing that two different hominin species were able to live as neighbors sharing a habitat, not as competitors who kept moving towards their own.
“It’s amazing that you could have two very similar, large-bodied hominin species in the same place,” said Kevin Hatala, first author of the fossil study published in the journal Science on Thursday.
“We see them in the same area of the sea, passing through this area in a few hours to another day. Maybe they would have known each other’s presence. They met and may have interacted,” added Hatala, a biology professor at Chatham University in Pittsburgh.
The first part of the discovery took place in July 2021 during excavations at Koobi Fora, on the eastern shore of Lake Turkana in Kenya, where the bones of several ancient relatives were found. That excavation revealed one hominin footprint, along with several other tracks made by large birds. The team decided to rebury the tracks with fine sand until deeper excavation was possible.
Excavations took place in 2022, when Hatala and his colleagues uncovered 23 square meters (248 square feet) of sediment, revealing 11 hominin tracks similar to the first one in a row that appeared to have been made by a single person, as well as three feet apart. which were oriented in a perpendicular direction.
The researchers also found 94 non-human species of birds and cattle- and animals such as horses. The large bird was 27 centimeters (10.6 inches) across and probably belonged to a species of giant scorpion known as Leptoptilos.
“There’s a long track with 12 (hominin) feet in it. It’s made of good walking … especially since they were walking through the mud. There’s nowhere clear at the end,” Hatala said.
“It’s hard to say what exactly they were doing, but they walked in that muddy area,” he said. “If you think about a lake shore or a modern beach, you have a kind of narrow area where the mud is perfect for making footfall. If you go too far this way, it’s too dry, if you go too far the other way, it’s too wet. And they are walking like a straight line in a good place for their feet to be prepared, which is lucky for us,” he said.
Three other road-facing tracks are scattered around the area. Hatala thinks that they were made by three different people, some of their tracks were probably destroyed by other animals that moved on the surface at the same time.
Members of the research team excavated the railroad site in 2022. – Neil T. Roach/Harvard University
It is preserved
Hatala and his companions could not keep up on foot. But Hatala said the fossils were found below – and therefore “slightly older” than – a layer of volcanic ash at the same site known as the Elomaling’a Tuff, which has been dated to 1.52 million years ago, according to the study.
However, the researchers said they are confident that the tracks were printed within hours to a few days of each other because there are no cracks on the feet, which would be the case if they were exposed to the air and dried under the sun. for a long time.
Instead, the scientists said that the prints were preserved in a similar way under the accumulation of mud, thanks to the fine and muddy sand that gently covered them after they were formed.
“This could be a delta system, with a lot of shallow water, less pressure in this area and lots of fine mud,” Hatala said.
The term hominin refers to all organisms in the human family that emerged after splitting from the ancestors of the great apes 6 to 7 million years ago. This group includes recently extinct species such as Neanderthals, which disappeared 40,000 years ago, and Australopithecus afarensis, represented by the famous Lucy skeleton in Ethiopia, which was 3.2 million years old.
Homo sapiens, our own species, is the only living species of hominin, making the idea of meeting another species from the same lineage all the more interesting to think about. Researchers have found some clues as to which ancient human groups crossed paths during this encounter.
Whose feet were they?
The team concluded that hominins of the type Homo erectus and the small-brained Paranthropus boisei made feet. P. bosei made a long track, while Homo erectus made another three feet, the study showed. The skeletal remains of these two species were found at the site.
However, it is not clear that the feet are made of two different types. Hatala, who is an expert in foot anatomy, determined that they showed different patterns of walking, standing and walking only after detailed 3D imaging and analysis.
Through experiments in the field and in the laboratory, he compared the footprints with those made by living people, including 59 of the Daasanach people in Ethiopia, who rarely wear shoes, as well as other fossilized hominin prints and tracks made by chimpanzees. .
Hatala found that the 12-print trackway made by a person whose feet did not fall into the various types seen in Homo sapiens, unlike the three legs spread out, arranged more closely to those made by living people.
“Homo erectus, from the neck down, looks similar to modern humans, and during this time, they are the best candidates to be our direct ancestors. We suspect that those human-like feet may be Homo erectus because some of their characteristics are human,” Hatala said.
“Paranthropus boisei, they look different. Most of its fossils are attributed to the skulls or teeth. They have very large jaws, very large teeth and large attachments for chewing muscles. It seems that they are used to eating a different diet than Homo erectus,” he said. Hatala explained that Bosei might be ate plant food, while Homo erectus was more of an omnivore.
Shown here is a fossil believed to have been created by Homo erectus, a type of early man. – Kevin G. Hatala/Chatham University
Hatala and his colleagues re-analyzed fossil data from the site and found evidence of two species that had coexisted at the site for a long time – perhaps within 100,000 years, he said.
“This is interesting to see and for us it means that direct competition between these two should have decreased, that they should have been living together and living in the same place. They were not chasing each other,” he said.
“It would have been a dangerous place, there would have been hippos, crocodiles, other kinds of dangerous animals living in those places,” Hatala added. “So there must be a request for both of them to go to these places many times for such a long time.”
The footprints are the first evidence that different hominin species interacted at the same time and place, avoiding predators and finding food in the ancient landscape, according to the study. Homo erectus continued to thrive for over 1 million years. Paranthropus boisei, however, became extinct within the next few hundred thousand years. Scientists don’t know why.
Briana Pobiner, a research scientist and museum educator at the Smithsonian National Museum of Natural History’s Human Origins Program, said it was “amazing” to find footprints of the same species but two walking in the same area.
“Perhaps, they actively competed for the same food; maybe they were just watching each other on the other side of the grassy area. Maybe they completely ignored each other,” said Pobiner, who was not involved in the research.
Although it is the first time that the footprints have shown that hominins of two species have directly met, the biological evidence has shown that Neanderthals are related to Homo sapiens and Denisovans, a poorly understood hominin known only from a few fossils. Denisova Cave in Siberia contained a girl who had a Neanderthal mother and a Denisovan father.
Perhaps, Pobiner said, P. boisei and H.
“These findings tell us that they were living in the same place, at the same time, and they were walking around each other,” he said.
“It’s impossible to go back in time to really observe these animals 1.5 million years ago – but to have both of their legs on top? That’s the next best thing.”
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