A new study published online in the Journal of Human Evolution refutes a long body of evidence, suggesting that a 9-million-year-old ape called Oreopithecus bambolii had the capabilities for bipedal walking.

“Our findings offer new insight into the Oreopithecus locomotor debate,” said lead author Dr Gabrielle Russo of the University of Texas at Austin.

“While it’s certainly possible that Oreopithecus bambolii walked on two legs to some extent, as apes are known to employ short bouts of this activity, an increasing amount of anatomical evidence clearly demonstrates that it didn’t do so habitually.”

Dr Russo and her colleague Dr Liza Shapiro, also from the University of Texas at Austin analyzed Oreopithecus fossils to see whether the ape possessed lower spine anatomy consistent with bipedal walking.

They compared measurements of its lumbar vertebrae and sacrum – a triangular bone at the base of the spine – to those of modern humans, fossil hominins, and a sample of mammals that commonly move around in trees, including apes, sloths and an extinct lemur.

“The lower spine serves as a good basis for testing the habitual bipedal locomotion hypothesis because human lumbar vertebrae and sacra exhibit distinct features that facilitate the transmission of body weight for habitual bipedalism,” Dr Russo said.

The study shows that the anatomy of Oreopithecus lumbar vertebrae and sacrum is unlike that of humans, and more similar to apes, indicating that it is incompatible with the functional demands of walking upright as a human does.

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Bibliographic information: Gabrielle A. Russo and Liza J. Shapiro. Reevaluation of the lumbosacral region of Oreopithecus bambolii. Journal of Human Evolution, published online July 23, 2013; doi: 10.1016/j.jhevol.2013.05.004