ASU scientists uncover new fossils – and a new species of ancient human ancestor
The fossils found in northeastern Ethiopia date between 2.6 to 2.8 million years ago and shed new light on human evolution
image:
Ledi-Geraru paleontological team searching for
fossils in the Lee Adoyta Basin where the genera
Homo and Australopithecus have been recovered.
Credit: Kaye Reed, Arizona State University
A team of international scientists has discovered new fossils at a field site in Africa that indicate Australopithecus, and the oldest specimens of Homo, coexisted at the same place in Africa at the same time — between 2.6 and 2.8 million years ago. The paleoanthropologists discovered a new species of Australopithecus that has never been found anywhere.
The Ledi-Geraru Research Project is led by scientists at Arizona State University and the site has revealed the oldest member of the genus Homo and the earliest Oldowan stone tools on the planet.
The research team concluded that the Ledi-Geraru Australopithecus teeth are a new species, rather than belonging to Australopithecus afarensis (the famous ‘Lucy’), confirming that there is still no evidence of Lucy’s kind younger than 2.95 million years ago.
“This new research shows that the image many of us have in our minds of an ape to a Neanderthal to a modern human is not correct — evolution doesn’t work like that,” said ASU paleoecologist Kaye Reed. “Here we have two hominin species that are together. And human evolution is not linear, it's a bushy tree, there are life forms that go extinct.”
Reed is a Research Scientist at the Institute of Human Origins and President’s Professor Emerita at the School of Human Evolution and Social Change at ASU. She has been co-director of the Ledi-Geraru Research Project since 2002.
Ledi-Geraru
What fossils did they find to help them tell this story? Teeth, 13 of them to be exact.
This field site has been famous before. In 2013 a team led by Reed discovered the jaw of the earliest Homo specimen ever found at 2.8 million years old. This new paper details new teeth found at the site that belong to both the genus Homo and a new species of the genus Australopithecus.
“The new finds of Homo teeth from 2.6 – 2.8 million year old sediments—reported in this paper—confirms the antiquity of our lineage," said Brian Villmoare, lead author and ASU alumnus.
“We know what the teeth and mandible of the earliest Homo look like, but that’s it. This emphasizes the critical importance of finding additional fossils to understand the differences
between Australopithecus and Homo, and potentially how they were able to overlap in the fossil record at the same location.”
The team cannot name the species yet based on the teeth alone; more fossils are needed before that can happen.
How old are the fossils?
How do scientists know these fossil teeth are millions of years old?
Volcanoes.
The Afar region is still an active rifting environment. There were a lot of volcanoes and tectonic activity and when these volcanoes erupted ash, the ash contained crystals called feldspars that allow the scientists to date them, explained Christopher Campisano, a geologist at ASU.
“We can date the eruptions that were happening on the landscape when they're deposited,” said Campisano, a Research Scientist at the Institute of Human Origins and Associate Professor at the School of Human Evolution and Social Change.
“And we know that these fossils are interbed between those eruptions, so we can date units above and below the fossils. We are dating the volcanic ash of the eruptions that were happening while they were on the landscape.”
Finding fossils and dating the landscape not only helps scientists understand the species – it helps them recreate the environment millions of years ago. The modern faulted badlands of Ledi-Geraru, where the fossils were found are a stark contrast to the landscape these hominins traversed 2.6 – 2.8 million years ago. Back then, rivers migrated across a vegetated landscape into shallow lakes that expanded and contracted over time.
Ramon Arrowsmith, a geologist at ASU, has been working with the Ledi-Geraru Research Project since 2002. He explained the area has an interpretable geologic record with good age control for the geologic time range of 2.3 to 2.95 million years ago.
“It is a critical time period for human evolution as this new paper shows,” said Arrowsmith, professor at the School of Earth and Space Exploration. “The geology gives us the age and characteristics of the sedimentary deposits containing the fossils. It is essential for age control.”
What’s next?
Reed said the team is examining tooth enamel now to find out what they can about what these species were eating. There are still remaining questions the team will continue to work on.
Were the early Homo and this unidentified species of Australopithecus eating the same things? Were they fighting for or sharing resources? Did they pass each other daily? Who were the ancestors of these species?
No one knows – yet.
“Whenever you have an exciting discovery, if you're a paleontologist, you always know that you need more information,” said Reed. “You need more fossils. That's why it's an important field to train people in and for people to go out and find their own sites and find places that we haven't found fossils yet.”
“More fossils will help us tell the story of what happened to our ancestors a long time ago — but because we're the survivors we know that it happened to us.”
The paper “New discoveries of Australopithecus and Homo from Ledi-Geraru, Ethiopia,” was published in the journal Nature. The team of scientists and field team working on this project is widespread and many work at Arizona State University, or are alumni of ASU.
ASU alumni and current faculty authors include; Associate Professor Brian Villmoare, Associate Professor Lucas Delezene, Professor Amy Rector, Associate Research Professor Erin DiMaggio, Research Professor David Feary, PhD Candidate Daniel Chupik, Instructor Dominique Garello, Assistant Professor Ellis M. Locke, Lecturer Joshua Robinson, Assistant Professor Irene Smail and the late Professor William Kimbel.
Reed and Campisano talk more about this project in an in-depth interview you can view here.
“These are teeth from Turtle Flat as we were
discovering them — you can see what the
ground behind looked like, and how amazing
it was that Omar Abdulla first saw them on
the surface,” said Amy Rector, Virginia Commonwealth University scientist.
Credit
Amy Rector, Virginia Commonwealth University
The 13 fossil teeth collected in the Ledi-Geraru Research Area from 2015-2018.
The collections at LD 750 and LD 760 localities represent a newly-discovered
species of Australopithecus. LD 302 and AS 100 represent early Homo already
known from the LD 350 mandible discovered in 2013.
Credit
Brian Villmoare: University of Nevada Las Vegas
Journal
Nature
Method of Research
Observational study
Subject of Research
Not applicable
Article Title
New discoveries of Australopithecus and Homo from Ledi-Geraru, Ethiopia
Article Publication Date
13-Aug-2025
Discovery of new fossils — and a new species of ancient human ancestor — reveals insights on evolution
UNLV anthropologist and international research team unearth Ethiopian fossils; findings published in Aug. 13 issue of Nature journal
image:
UNLV anthropology professor Brian Villmoare (right, in blue shirt) and colleagues screening at the Ledi-Geraru research site in 2018.
view moreCredit: Image courtesy of Brian Villmoare/UNLV
The discovery of new fossils and a new species of ancient ancestor may help shift the perception of human evolution from linear evolution to that of a tree with many branches, new UNLV research published today in the journal Nature shows.
UNLV anthropologist Brian Villmoare and a team of international scientists discovered new fossils at a field site in Ethiopia that indicate Australopithecus, and the oldest specimens of Homo, coexisted between 2.6 and 2.8 million years ago at the same place in Africa.
The scientists found 13 teeth at the Ledi-Geraru site and determined that, although some belong to the genus Homo, a set of upper and lower teeth belong to a new species of the genus Australopithecus. This new species is distinct from the well-known Australopithecus afarensis (the famous ‘Lucy’), which last appears at roughly 2.95 million years ago and was discovered in nearby Hadar.
The presence of both species in the same location shows that human evolution is less linear and more tree-like, said Villmoare, associate professor of anthropology and lead author of the paper.
“We used to think of human evolution as fairly linear, with a steady march from an ape-like ancestor to modern Homo sapiens. Instead, humans have branched out multiple times into different niches. Our pattern of evolution is not particularly unusual, and what has happened to humans has happened to every other tree of life,” he said.
“This is what we should be finding in the human fossil record," Villmoare said. "Nature experimented with different ways to be a human as the climate became drier in East Africa, and earlier more ape-like species went extinct.”
The Ledi-Geraru site is the same field site where a team of researchers discovered the jaw of the earliest Homo specimen ever found at 2.8 million years old. Villmoare has worked with the Ledi-Geraru Research Project and scientists at the Institute of Human Origins at Arizona State University since 2002.
“The new finds of Homo teeth from 2.6–2.8 million-year-old sediments—reported in this paper—confirms the antiquity of our lineage," he said.
“We know what the teeth and mandible of the earliest Homo look like, but that’s it. This emphasizes the critical importance of finding additional fossils to understand the differences between Australopithecus and Homo, and potentially how they were able to overlap in the fossil record at the same location.”
The researchers haven’t named the species yet. More fossils and further study are needed.
About the Study
“New discoveries of Australopithecus and Homo from Ledi-Geraru, Ethiopia,” by Villmoare et al., was published Aug. 13 in the journal Nature. The scientists and field team working on this project span multiple universities.
Journal
Nature
Article Title
New discoveries of Australopithecus and Homo from Ledi-Geraru, Ethiopia,
Article Publication Date
13-Aug-2025
Discovery confirms early species of hominins co-existed in Ethiopia
New findings document the geological age, context and anatomy of hominin fossils discovered at the Ledi-Geraru Research Project, Ethiopia
University of Arkansas
image:
Lucas Delezene, associate professor of anthropology.
view moreCredit: University Relations
While we know much of the story of how humans evolved, the puzzle is still missing critical pieces. For example, fossil evidence for human evolution between 2 and 3 million years ago is patchy. It’s frustrating because we know that the branch of the hominin family tree that includes humans, or Homo sapiens, appears in the fossil record for the first time in this period.
Today, Homo sapiens (which anthropologists shorten to Homo), is the only hominin species alive. But in the past, Homo wasn’t alone. We coexisted and competed with other branches of the human family tree. Research supported by the National Science Foundation and the Leakey Foundation and published in Nature now fills in a piece of the ongoing evolutionary puzzle, placing two early species of hominin side-by-side.
A team working in the Afar Region of Ethiopia, at the site of Ledi-Geraru, reports hominin fossils that date between 2.6 and 3.0 million years old. Lucas Delezene, an associate professor of anthropology at the University of Arkansas, was second author on a paper that incorporated the work of more than 20 researchers from North America, Africa and Europe.
The team found fossils of Homo that confirm the earliest evidence for the human lineage at 2.8 million years ago as well as evidence of Homo at 2.6 million years ago, solidifying the antiquity of Homo. Unexpectedly, the team also found evidence that Homo overlapped at the site with a different type of hominin, Australopithecus, at 2.6 million years ago.
This was a surprise because Australopithecus was thought to be extinct in the area by about 3 million years ago. The famous Australopithecus fossil known as Lucy was found at a nearby site, but her species disappeared from the fossil record at 3 million years ago.
“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.
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.
Journal
Nature
Method of Research
Observational study
Subject of Research
People
Article Title
New discoveries of Australopithecus and Homo from Ledi-Geraru, Ethiopia
Article Publication Date
13-Aug-2025
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