Approximately seven million years prior, a diminutive organism navigated treacherous floodplains in Bulgaria, evading predators like wildcats and hyenas, with evidence suggesting it may have done so using bipedal locomotion.
A recently documented fossilized femur provides compelling indications that this now-extinct primate, estimated to have weighed around 24 kilograms (53 pounds) and provisionally identified as Graecopithecus freybergi, possessed several anatomical characteristics consistent with habitual upright walking.
In a recent communiqué, the researchers involved in the analysis of this ancient thigh bone propose that this compact hominin might represent our earliest progenitor; however, this assertion is not universally accepted.
“At an age of 7.2 million years, this ancestor, which we categorize within the genus Graecopithecus, could potentially be the oldest recognized human ancestor,” stated David Begun, a paleoanthropologist affiliated with the University of Toronto and a co-author of the study.
The proposed lineage of Graecopithecus has been a subject of debate for a considerable duration. Counterarguments from other scientists contest the researchers’ conclusions, including the implication that the origins of humanity lie in the Balkans rather than Africa, citing various factors, notably a deficiency in empirical support.
Prior to this recent find, Graecopithecus was known only from two paleontological specimens: a mandible discovered in Greece in 1944 and a premolar tooth unearthed in Bulgaria in 2012. The latter was retrieved from the Azmaka excavation site, identical to the location where the aforementioned fossil femur was discovered in 2016.
Within the scope of this newest investigation, the scientists characterize the owner of the ancient thighbone as a mature female, diminutive in stature, comparable to a chimpanzee. For comparative purposes, her femur bore a resemblance in size to those of the carnivorous mammals that roamed these plains, including giant otters, proto-hyenas, and early badger descendants.
Nevertheless, the morphology of the femur offers more significant insights than its dimensions. For instance, it exhibits a comparatively elongated femoral neck, which serves as the connection between the diaphyseal shaft of the thighbone and the femoral head, subsequently articulating with the hip socket. An extended femoral neck is indicative of bipedalism, as it facilitates enhanced freedom of movement in the leg.
This anatomical feature also signifies an evolutionary compromise between structural robustness and kinetic range. As hominins evolved towards modernity, they achieved a greater amplitude of motion at the cost of inherent stability and arboreal locomotion capabilities.
The research team further points to the attachment points for the gluteal musculature, which appear to be anatomically suited for upright posture. Moreover, the cortical thickness of the bone’s outer layer suggests the presence of stresses associated with terrestrial locomotion.
However, the fossil also retains characteristics common to quadrupedal species. Within the published study, the investigators describe the femur as representing a “transitional phase between African great apes and habitual bipedal hominins.”
The Azmaka environs during the late Miocene epoch were characterized by sparse woodlands giving way to open savannahs, lending credence to the hypothesis that bipedalism may have emerged with the transformation of arboreal landscapes into grasslands.
Despite potentially abandoning arboreal life, this primate’s gait would not have precisely mirrored our own. Its femoral traits suggest facultative bipedal locomotor capabilities, implying it could ambulate upright when advantageous, while also navigating the terrain using all four limbs.
It is plausible that this individual adopted an upright stance to survey its surroundings for predators, to more efficiently procure sustenance in increasingly open environments, or to transport its young between arboreal nesting sites.
Considering the significant environmental and climatic transformations of that era, it is conceivable that Graecopithecus also migrated from the Balkans to Africa, the researchers posit.
“We are aware that substantial climatic shifts in the eastern Mediterranean and western Asia resulted in the intermittent emergence of extensive semi-arid regions and deserts between 8 and 6 million years ago,” commented Madelaine Böhme, a paleontologist at the University of Tübingen and co-author of the investigation.
“This phenomenon precipitated multiple migratory episodes of Eurasian mammals into Africa, thereby establishing the foundational elements of the contemporary mammalian fauna of African savannas.”
However, on previous occasions when Begun and Böhme presented similar hypotheses, other specialists expressed skepticism.
“The presence of a hominin or even a hominine (a modern African ape) ancestor situated in a relatively isolated region of southern Europe presents significant geographical inconsistencies as the progenitor of modern African apes, or indeed the earliest ancestor of African hominins,” Rick Potts of the Smithsonian Institution conveyed to The Washington Post in 2017.
In summation, this paleontological discovery serves as a potent reminder of the inherent uncertainty, ongoing debate, and potential variability surrounding the narrative of human origins. Any given day could yield a novel fossil discovery that sparks intensified discourse regarding our ancestral history.
This research has been formally published in the peer-reviewed journal Paleobiodiversity & Paleoenvironments.
