The study has already stirred attention beyond academic circles, with Bulgaria’s national news agency BTA highlighting the find as potential evidence that the “earliest bipedal hominins lived in the Balkans.” At the same time, the authors stress that the fossil doesn’t look like a modern human leg; instead, it suggests a complex locomotor repertoire at the edge of the human lineage.
A Femur From Azmaka and a “Transitional” Gait
The fossil comes from Azmaka, near the town of Chirpan in Bulgaria’s Upper Thracian Plain, and is dated to roughly 7.2 million years ago (Late Miocene). In the new analysis, the team describes it as the first known postcranial (non-tooth, non-skull) element from this locality that can be tentatively linked to cf. Graecopithecus. This is key because earlier debates around Graecopithecus leaned heavily on dental and jaw traits, not locomotion explains a University of Tubingen release.
The authors argue that the femur lacks key specializations typical of arboreal quadrupeds and, taken as a whole, “indicates a transitional form of bipedalism.” In the Bulgarian news coverage, lead author Prof. Nikolai Spassov notes that the bone shows a “unique combination” of traits linked to both terrestrial quadrupedal movement and bipedal walking. They also report CT-based evidence from the femoral neck that they say sets it apart from the femora of tree-dwelling apes.
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The Graecopithecus femur from Azmaka, Bulgaria, (left) in comparison with that of Lucy (Australopithecus afarensis) (middle) and the thighbone of a chimpanzee (right). (N. Spassov, D. Youlatos, M. Böhme, R. Bogdanova, L. Hristova, D. Begun/Palaeobiodiversity and Palaeoenvironments)
One eye-catching detail is the researchers’ estimate that the bone likely belonged to a small female, about 24 kg, and nicknamed “Diva.” Spassov noted the fossil seems to sit somewhere between older, more arboreal forms and later, more committed bipeds, making it intriguing without being a definitive “smoking gun.”
The Balkans Place in the Late Miocene
The paper places the femur in a wooded-grassland savanna setting, arguing that early terrestrial bipedalism could have emerged in a relatively open, non-forested landscape. In the abstract, the authors also connect this timing to wider Late Miocene biogeography, when intercontinental dispersals between Eurasia and Africa were reshaping mammal communities. In other words, “Balkan bipedalism” is being framed not as an isolated oddity, but as part of broader ecological and climatic pressures.
In BTA’s report, the excavation team describes the Azmaka fauna as savanna-like, including gazelles and other bovids, hipparions, giraffes and rhinos. The researchers further argue that the Balkans and nearby Anatolia acted as a crossroads for species moving between continents, and they suggest that a bipedal hominine could have dispersed southward into Africa before later phases of human evolution played out there. That dispersal idea is also echoed in a separate Ancient Origins discussion of eastern Mediterranean primates and possible migrations into Africa. BTA Ancient Origins
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Lower jaw and tooth (holotype) of Graecopithecus freybergi, long central to debates about early European hominins. (Fuss, Spassov, Begun & Böhme/CC BY 4.0)
What this means for ‘Out of Africa’, and what it doesn’t
Even if the Azmaka femur truly reflects early bipedal ability, it doesn’t automatically rewrite the entire human story. The fossil record around 6–7 million years ago is famously sparse and frequently contested, and the field has learned (sometimes painfully) that single bones can support multiple, competing reconstructions. A recent Scientific American overview of the debate around Sahelanthropus underscores how even well-known candidates can swing in and out of favor as methods and interpretations change.
What the Bulgarian femur does provide is a concrete, testable specimen that ties “Balkan bipedalism” to an anatomical signal rather than inference from teeth alone. Whether it ends up as an ancestral clue, a parallel experiment in upright walking, or something else entirely will likely depend on what comes next: more fossils from Azmaka and comparable Balkan sites, and, crucially, clearer links between teeth, jaws and postcranial bones. For now, it is best read as an invitation to dig deeper, not a final verdict.
Top image: Scenery at Zgorigrad Village, Vrachanski Balkan National Park, Bulgaria. Right; Views of the femur from the study. Source: Adam Jones/CC BY-SA 2.0 Right; Spassov et al
By Gary Manners
References
Bulgarian Telegraph Agency (BTA). 2026. Earliest Bipedal Hominins Lived in the Balkans. Available at: https://www.bta.bg/en/news/culture/1076655-earliest-bipedal-hominins-lived-in-the-balkans
Cottier, C. 2026. Earliest Human Ancestor May Have Walked on Two Legs. Available at: https://www.scientificamerican.com/article/earliest-human-ancestor-may-have-walked-on-two-legs/
University of Tübingen, 2026. Did the first human ancestor originate in the Balkans? New fossil shows evidence of bipedalism. Available at: Did the first human ancestor originate in the Balkans? – New fossil shows evidence of bipedalism
Spassov, N., Youlatos, D., Böhme, M., Bogdanova, R., Hristova, L., Begun, D.R. 2026. An early form of terrestrial hominine bipedalism in the Late Miocene of Bulgaria. Available at: https://link.springer.com/article/10.1007/s12549-025-00691-0
