A. Hammond/© AMNH
More than 60 years ago, researchers found a surprisingly complete, but extremely flattened, fossilized skeleton of an ancient ape embedded in a slab of coal in a part of Italy that used to be an island. This unique fossil of Oreopithecus bambolii—a primate that lived between 6 and 8 million years ago—has confounded scientists for years, especially as it pertains to how the animal moved. Did it walk upright on two legs? Or did it possibly move along under branches like a sloth?
“If you can name a locomotor behavior that’s been attributed to a primate, it probably has been applied to this fossil,” said Ashley Hammond, an assistant curator in the Museum’s Division of Anthropology.
A new study in the journal Proceedings of the National Academy of Sciences and led by Hammond and Museum senior research scientist Sergio Almécija provides new insights about Oreopithecus: the extinct primate likely was a climber, but it moved differently from all living species of apes.
The deformation of the flattened skeleton specimen and its unusually shaped teeth, have made it difficult to determine how Oreopithecus, which is the latest-known hominoid (which includes apes and humans) from Europe, was related to other species, what it ate, and how it behaved.
For the study, scientists took a comprehensive look at all of the vertebrae and pelvic fossil material for Oreopithecus, including the Italian specimen—housed at the Natural History Museum of the University of Florence—and pieces found from other Oreopithecus individuals that are part of the collections at the Natural History Museum of Basel, Switzerland. The Italian skeleton has been newly prepared over the course of several years with a focus on the pelvic elements, and Hammond and Almécija were among the first outside researchers to access it since that work took place.
“We were able to get a glimpse of anatomy that couldn’t be appreciated before the new preparation of the fossil,” Almécija said. “What we see is a combination of features that is new to science, providing a much-needed view of how this late Miocene ape looked.”
“It’s also important to consider fossil apes in the context of early hominins because it gives us a guidepost as to where early hominins started off,” Hammond explained. “Oreopithecus is not an ancestor of hominins, but it gives us a window to what was happening in that time period.”
The researchers found that the body form of Oreopithecus isn’t seen in living apes. It had a more flexible lumbar region, giving it greater behavioral diversity. With limb proportions intermediate between modern-day orangutans and bonobos, it would have been a skilled climber. But its shorter fingers probably made it less suited for hanging below the branches. Its torso shape was similar to siamangs (the largest of the “lesser apes” that also includes gibbons).
However, in terms of overall body size, Oreopithecus was bigger than the “lesser apes,” and would have been on the lower end of the size range of great apes alive today. “Oreopithecus might give us an idea of what it means to be an ape at this particular body size,” Hammond said.