Walking upright is considered a core characteristic of the first prehumans; it distinguished them from prehistoric apes. But which hominids were the first to develop this ability is still a matter of debate. Now a fossil femur discovered in Bulgaria could upend common assumptions. The 7.2 million year old fossil proves that the European hominid Graecopithecus freybergi could already walk on two legs. Was he the first real pre-human?
When and where did the first hominin, the first prehuman who no longer belonged to the great apes, develop? So far, neither the location nor the exact time of this evolutionary milestone in human history has been clarified. For a long time, Ardipithecus ramidus, which lived in East Africa around 4.4 million years ago, was considered the first primate to temporarily walk upright and thus the first true prehuman. However, fossil analyzes now suggest that the Central African Sahelanthropus tchadensis also mastered bipedal walking around six million years ago. Both prehumans supported the assumption that the first prehumans developed in Africa.
Leg bones with features of upright walking
However, in 2017, paleoanthropologists in Greece and Bulgaria discovered fossils of another hominid, around 7.2 million years old. The lower jaw and several molars of this creature, named Graecopithecus freybergi, showed features that differed from those of prehistoric apes and were more human-like. However, because no other skeletal parts were found, it was not possible to determine whether this hominid could already walk upright. Now a team led by Nikolai Spassov from the Bulgarian National Museum of Natural History in Sofia has also discovered a femur bone in the Azmaka site in southern Bulgaria.
The fossil bone is also around 7.2 million years old and comes from an individual weighing only around 24 kilograms. According to the researchers, it could be a lighter, female specimen of Graecopithecus. Further analysis showed that this bone has unmistakable features of a bipedal primate. “A number of external and internal morphological features, such as the elongated and upright femoral neck, special attachment points for the gluteal muscles or the thickness of the outer bone layer, show similarities to bipedal fossil human precursors and humans,” says Spassov.
Was Graecopithecus the first prehuman?
The new find suggests that Graecopithecus freybergi was no longer a prehistoric ape, but rather an early prehuman or at least a transitional form. “Graecopithecus represents a stage in human evolution that stands between our tree- and ground-dwelling ancestors, such as the almost twelve-million-year-old Danuvius guggenmosi from the Hammerschmiede in the Allgäu, and more recent finds from East Africa,” says co-author David Begun from the University of Toronto. “You could definitely call it the missing link.”
If this is confirmed, Graecopithecus could have been the oldest known prehuman, even older than the African Sahelanthropus. According to the researchers, Graecopithecus could have evolved in the Balkan region from prehistoric great apes such as Ouranopithecus and Anadoluvius, which occurred in the Balkans and Anatolia eight to nine million years ago. According to Spassov and his colleagues, it could even be that Graecopithecus and similar hominid forms also provided the impetus for the development of African prehumans. “We know that large-scale climate changes in the eastern Mediterranean and western Asia eight to six million years ago led to the periodic emergence of extensive semi-deserts and deserts,” explains co-author Madelaine Böhme from the University of Tübingen. “This development initiated several waves of expansion of Eurasian mammals into Africa.”
In the course of this migration, Graecopithecus could also have reached Africa from the Balkans – and then contributed to the emergence of other prehumans such as the Sahelanthropus or Orrorin. Later, in East Africa, the Australopithecus, the pre-human beings that became our ancestors, developed from these forms.
Source: Eberhard Karls University of Tübingen; Specialist article: Palaeobiodiversity and Palaeoenvironments, doi: 10.1007/s12549-025-00691-0