In 2009, paleoanthropologists discovered eight bones from the foot of an ancient human ancestor in 3.4 million-year-old sediments at the Woranso-Mille paleontological site in Ethiopia’s Afar Rift. According to new research, the fossil – named Burtele’s foot – belongs to a species of hominid called I’m not saying Australopithecus. The discovery provides further evidence that two hominid species — I’m not saying Australopithecus And Australopithecus afarensis — coexisted at the same time and in the same region.
I’m not saying Australopithecus And Australopithecus afarensis. Image credit: Gemini AI.
“When we found the foot in 2009 and announced it in 2012, we knew it was different from Lucy’s species, Australopithecus afarensiswhich is widely known at that time,” said Professor Yohannes Haile-Selassie of Arizona State University.
“However, it is not common in our field to name a species based on postcranial elements, so we were hoping to find something above the neck in clear association with the foot.
“The skull, jaws and teeth are generally the elements used in species recognition.”
“When the Burtele Foot was announced, some teeth had already been found in the same area, but we were not convinced they came from the same level of sediment.”
“Then, in 2015, scientists announced a new species, I’m not saying Australopithecusfrom the same region but did not include the foot in this species although some specimens were found very close to the foot.
“Over the last 10 years of returning to the field and discovering more fossils, we now have specimens that we can confidently associate with Burtele’s Foot and the species. I’m not saying Australopithecus.”
I’m not saying Australopithecus‘s foot is more primitive than the feet of Lucy’s species, Australopithecus afarensis.
It retains an opposable big toe, important for climbing. But once on the ground, I’m not saying Australopithecus walked on two legs and probably grew on his second digit rather than his big toe like we modern humans do today.
“The presence of a removed big toe Ardipithecus ramidus “It was a big surprise because 4.4 million years ago there was still a hominid ancestor that retained an opposable big toe, which was totally unexpected,” Professor Haile-Selassie said.
“Then 1 million years later, 3.4 million years ago, we found Burtele’s foot, which is even more surprising.”
“This is a time when we see species like Australopithecus afarensis whose limbs were entirely bipedal with an adducted big toe.
“This means that bipedalism – walking on two legs – in these early human ancestors manifested itself in various forms.”
“The whole idea of finding specimens like Burtele’s foot tells you that there were many ways to walk on two legs on the ground, but there was only one way until later.”
To get an overview of the diet of I’m not saying Australopithecusthe authors sampled eight of the 25 teeth found in the Burtele localities for isotopic analysis.
The process involves cleaning the teeth, making sure to only remove the enamel.
“I sample the tooth with a dental drill and a very small drill bit (<1mm) – this equipment is the same type that dentists use to work on your teeth,” said Professor Naomi Levin of the University of Michigan.
“With this drill, I carefully remove small amounts of powder. I store this powder in a plastic vial and bring it back to our laboratory for isotope analysis.”
“The results were surprising: while Lucy’s species was a mixed feeder, feeding on C3 plants (resources from trees and shrubs) and C4 plants (tropical grasses and sedges), I’m not saying Australopithecus used resources that are more on the C3 side.
“I was surprised that the carbon isotope signal was so clear and so similar to carbon isotope data from older hominids. Australopithecus ramidus And Australopithecus anamensis.”
“I thought that the distinctions between the diet of I’m not saying Australopithecus And Australopithecus afarensis would be more difficult to identify, but the isotopic data clearly show that I’m not saying Australopithecus did not access the same range of resources as Australopithecus afarensiswhich is the first hominid to use C4 grass food resources.
Another key data analysis involved carefully establishing the age of the fossils and understanding the ancient environment in which ancient hominids lived.
“We have done considerable field work at Woranso-Mille to establish the relationship between different fossil layers, which is crucial to understanding when and in what contexts different species lived,” said Professor Beverly Saylor of Case Western Reserve University.
In addition to the 25 teeth found in Burtele, researchers also discovered the jaw of a 4.5-year-old juvenile, which, based on the anatomy of the teeth, clearly belonged to I’m not saying Australopithecus.
“For a juvenile hominid of this age, we could see clear evidence of a growth mismatch between the front teeth (incisors) and the back chewing teeth (molars), much like we see in living apes and other primitive australopiths, like Lucy’s species,” said Professor Gary Schwartz of Arizona State University.
“I think the biggest surprise was that, despite our growing awareness of the diversity of these early australopith species (i.e., early hominids) – in their size, in their diet, in their locomotor repertoires, and in their anatomy – these early australopiths appear to be remarkably similar in the way they grew.”
An article on the results was published this week in the journal Nature.
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Y. Haile-Selassie and others. New discoveries shed light on diet and locomotion I’m not saying Australopithecus. Naturepublished online November 26, 2025; doi: 10.1038/s41586-025-09714-4
