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New fossils from Ethiopia reveal that early Homo and Australopithecus species lived side by side 2.6 million years ago.
Credit: Shutterstock
New findings reveal the geological age, context, and anatomy of hominin fossils discovered at the Ledi-Geraru Research Project in Ethiopia.
Although scientists have uncovered much of the story of human evolution, several key chapters are still missing. One major gap lies between 2 and 3 million years ago, a period for which fossil evidence remains scarce. This absence is especially significant because it marks the era when the branch of the hominin family tree that includes modern humans, or Homo sapiens, first appears in the fossil record.
Today, Homo sapiens (commonly referred to by anthropologists as Homo) is the only surviving member of the hominin lineage. In earlier times, however, our ancestors shared the Earth with other related species, sometimes competing and coexisting with them. Recent research supported by the National Science Foundation and the Leakey Foundation, and published in Nature, helps close one of these evolutionary gaps by revealing two early hominin species that lived side by side.
At the Ledi-Geraru site in Ethiopia’s Afar Region, an international research team discovered hominin fossils dated between 2.6 and 3.0 million years old. Lucas Delezene, an associate professor of anthropology at the University of Arkansas, served as the study’s second author, contributing alongside more than 20 scientists from North America, Africa, and Europe.
The findings include fossils of Homo that establish the oldest confirmed evidence of our lineage at 2.8 million years ago, with additional remains dating to 2.6 million years ago. These discoveries strengthen the case for Homo’s deep evolutionary roots. Even more surprising, the team found that Homo lived in the same region at the same time as another hominin, Australopithecus, around 2.6 million years ago.
This overlap challenges long-held assumptions, as Australopithecus was believed to have vanished from the area roughly 3 million years ago. The famous Australopithecus specimen known as Lucy was discovered nearby, yet her species was thought to have disappeared from the fossil record by that point.
Rethinking Evolution’s “Linear” Model
Credit: University of Arkansas
“People often think evolution is a linear progression,” explains Delezene, “like the March of Progress, but in reality humans are only one species that make up a twig of a bigger family tree — it’s quite bushy and what we found is another twig that was previously unknown. The idea that Homo appears and immediately spreads around the planet and replaces all other hominin species is not accurate. Homo lived side-by-side with many other hominin species throughout Africa. What’s neat is that Homo overlaps with different hominin species in different places.”
For example, from southern Ethiopia to southern Africa, the earliest species of Homo overlapped with a hominin known as Paranthropus, which is well known for its massive teeth and chewing muscles and a diet reliant on grass in some parts of its range. However, in the Afar Region of Ethiopia, no Paranthropus fossils have ever been found.
Instead, the team working at Ledi-Geraru found that Homo overlap with a different type of hominin, Australopithecus. How all of these hominin species divided up resources is the question of ongoing research. Did Homo nod to the other hominin species on their way to hunting and gathering in the morning, or did the various species consume similar resources? Did Homo eat the same things in Ethiopia, where it coexisted with Australopithecus as it did in the south where it coexisted with Paranthropus, or was its diet flexible?
We know that Homo eventually becomes a culturally reliant tool user and occasionally consumed meat. But the oldest Homo fossils at Ledi-Geraru predate any evidence of tool manufacture or meat consumption. Did Homo evolve those traits to avoid competing with other hominin species? Competition among these various hominin species likely set the stage for the evolution of the traits that ultimately made humans a globally widespread and successful species.
Fossils in Focus: The Teeth Tell the Story
The fossils published in the Nature paper are all teeth. Teeth are often the best-preserved fossils because their enamel coating provides better protection from the ravages of time and the elements.
Delezene, a hominin dental expert, says, “When we get down to the picky details, the teeth of Homo and Australopithecus look different. The differences are subtle, but once you see them, you can’t unsee them. They’re very consistent.”
While the new fossils fill in a piece of the puzzle, there is still a long way to go before we have a complete picture of human evolution. While there is evidence for the teeth of early Homo and the new Australopithecus, the team doesn’t know what their heads or the rest of their bodies looked like. The multi-national collaboration, done in partnership with the local community of Afar people, will continue its work looking for more fossils, ideally with continued funding.
“People often think evolution is a linear progression,” explains Delezene, “like the March of Progress, but in reality humans are only one species that make up a twig of a bigger family tree — it’s quite bushy and what we found is another twig that was previously unknown. The idea that Homo appears and immediately spreads around the planet and replaces all other hominin species is not accurate. Homo lived side-by-side with many other hominin species throughout Africa. What’s neat is that Homo overlaps with different hominin species in different places.”
For example, from southern Ethiopia to southern Africa, the earliest species of Homo overlapped with a hominin known as Paranthropus, which is well known for its massive teeth and chewing muscles and a diet reliant on grass in some parts of its range. However, in the Afar Region of Ethiopia, no Paranthropus fossils have ever been found.
Instead, the team working at Ledi-Geraru found that Homo overlap with a different type of hominin, Australopithecus. How all of these hominin species divided up resources is the question of ongoing research. Did Homo nod to the other hominin species on their way to hunting and gathering in the morning, or did the various species consume similar resources? Did Homo eat the same things in Ethiopia, where it coexisted with Australopithecus as it did in the south where it coexisted with Paranthropus, or was its diet flexible?
We know that Homo eventually becomes a culturally reliant tool user and occasionally consumed meat. But the oldest Homo fossils at Ledi-Geraru predate any evidence of tool manufacture or meat consumption. Did Homo evolve those traits to avoid competing with other hominin species? Competition among these various hominin species likely set the stage for the evolution of the traits that ultimately made humans a globally widespread and successful species.
Fossils in Focus: The Teeth Tell the Story
The fossils published in the Nature paper are all teeth. Teeth are often the best-preserved fossils because their enamel coating provides better protection from the ravages of time and the elements.
Delezene, a hominin dental expert, says, “When we get down to the picky details, the teeth of Homo and Australopithecus look different. The differences are subtle, but once you see them, you can’t unsee them. They’re very consistent.”
While the new fossils fill in a piece of the puzzle, there is still a long way to go before we have a complete picture of human evolution. While there is evidence for the teeth of early Homo and the new Australopithecus, the team doesn’t know what their heads or the rest of their bodies looked like. The multi-national collaboration, done in partnership with the local community of Afar people, will continue its work looking for more fossils, ideally with continued funding.
The birth of modern Man
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