The first apes to walk upright may have evolved in Europe
Illustration of Graecopithecus freybergi, an ape that lived 7.2 million years ago in southeastern Europe
Velizar Simeonovski, Chicago
Apes may have walked upright in what is now Bulgaria 7.2 million years ago. That’s according to researchers who found a leg bone that shows signs of bipedal walking.
The leg bone is older than all known hominid fossils, including all those from Africa. This suggests that bipedalism – a crucial step in human evolution – may have evolved in Europe rather than Africa.
“The oldest indications of bipedalism are found in Europe,” explains Madelaine Böhme of the University of Tübingen in Germany.
Böhme and his colleagues have been excavating at Azmaka, near Chirpan, in southern Bulgaria, since 2008. The site features a layer of sediments deposited by the river, about 20 meters thick.
In 2016, the team discovered a single femur, or right femur, buried in 7.2 million-year-old sands. The femur is 21.5 centimeters long and almost complete, with only part of the lower end missing. The team nicknamed the individual “Diva”.
“It’s a very, very nice discovery,” says Clément Zanolli of the University of Bordeaux in France, who was not involved in the study. “This femur is pretty well preserved, and it’s really very rare in the Miocene fossil record for hominids.”
Europe was once home to many different apes, but by 7.2 million years ago many of them had become extinct. Today, our closest ape relatives all live in Africa. Likewise, all early ancient humans, or hominids, originated in Africa.
The only monkey identified at Azmaka is Graecopithecus freybergia little-known species known only from a damaged jaw from Greece, a tooth from North Macedonia, and, from Azmaka, a single tooth. Böhme’s team therefore suggests that the femur is probably Graecopithecus.
“This is the most parsimonious choice we can make at the moment,” Zanolli says, but he emphasizes that more fossils will be needed before we can have confidence.
“The association between these fossils is vague,” says Kelsey Pugh of OCAD University in Toronto, Canada.
Femur bone Graecopithecus (left), Lucy (Australopithecus afarensis, in the middle) and a chimpanzee (right). A longer femoral neck (shown in red) may be associated with upright walking
Spassov et al. 2026
Böhme’s team measured the femur in detail and performed a CT scan. Researchers found several features that they believe prove it belonged to a bipedal animal.
For example, at the top of the bone, a short neck extends sideways and then expands into a rounded bulb that would have inserted into the pelvis. The neck has a fairly long, straight section – seen in bipedal hominids, but not in knuckle-walking apes – that can support a vertical load. Likewise, the outer layer of bone is thicker at the bottom of the neck than at the top, which also helps it support weight.
Additionally, there is a ridge at the back of the bone, where the gluteal muscles would have attached. “They are important because they keep the back straight,” explains Böhme.
Other researchers are intrigued but not convinced. “This femur has a number of characteristics,” says Zanolli. “Some look like bipeds, but others look like quadrupeds. So it’s quite difficult to know exactly what their locomotor behavior was.”
The more we study apes that went extinct millions of years ago, the more we discover that bipedalism is difficult to diagnose from isolated bones, Pugh says. Many features thought to be unique to bipedal hominids have been discovered in quadrupedal apes. This means that researchers must determine which characteristics are truly diagnostic and identify several for each species. “We’re raising the standard of what’s required,” she says, and so far there isn’t enough femur to convince her.
Much of this reassessment is due to an ongoing dispute over Sahelanthropus chadensis. Known from only one location in Chad, this species is the oldest species generally considered to be a hominid rather than an ape. It lived 7 million years ago, a little more recently than the Azmaka specimen. A Sahelanthrope The femur was discovered and paleoanthropologists have argued for years about whether it shows signs of bipedalism.
Böhme and his colleagues spent years trying to establish that key steps in early hominid evolution took place in Europe. They reported evidence of hominid-like characteristics in the Graecopithecus jaw, which have been contested because the bone is very damaged. They also described another European ape, Danuvius guggenmosi from 11.6 million years ago, as being able to stand and walk along tree branches.
Subsequently, these early hominids may have migrated to Africa – perhaps due to climate changes that occurred 8.75 to 6.25 million years ago, the team suggested – where they gave rise to all later hominids, including us.
Many other animals moved between Africa and Eurasia, Zanolli says. “If wildlife can do it, why not hominids?
However, Pugh argues that we need to consolidate the evidence for bipedalism in Europe and find more specimens of bipedalism. Graecopithecusso that we can understand its connections to other apes and hominids. Without this, it is premature to develop detailed scenarios, she believes.
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