Human Evolution’s Cookie Monster, Oreopithecus

For the past 60 years, scientists have argued over the enigmatic, human-like fossils of the nine-million-year-old Italian ape

The skeleton of Oreopithecus bambolii
The skeleton of Oreopithecus bambolii Image courtesy of Wikicommons

In the 1950s, a Swiss paleontologist named Johannes Hürzeler made an intriguing discovery. In a coal mine in the Tuscany region of Italy, he unearthed dozens of fossils, including a largely complete skeleton, belonging to an ape species named Oreopithecus bambolii (the name refers to the Greek word for hill or mountain, not the delicious chocolate cookie). A jaw of the species had been found in 1872, but the new treasure trove of fossils painted an unusual picture of the ape. The ape’s features implied it walked upright on two legs, just like humans. In fact, Hürzeler thought the nine-million-old species might have been a human ancestor. Others concluded it was just an ape that had evolved human-like characteristic due to convergent evolution. Still others who saw the fossils saw no human-like traits at all.

More than 50 years later, the debate continues.

In the 1990s, researchers Meike Köhler and Salvador Moyà-Solà, both of the Miquel Crusafont Catalan Institute of Paleontology in Spain, restored and reanalyzed a collection of Oreopithecus fossils housed in a Swiss museum. They claimed features of the ape’s pelvis, spine, legs and feet resembled those of australopithecines and modern humans, new evidence that Oreopithecus was capable of walking upright and probably did so habitually. Subsequent work on hand fossils suggested the ape also had the precise gripping skills that allow humans to thread a needle or turn a key in a lock.

Despite the similarities to humans, Köhler and Moyà-Solà argued that Oreopithecus was indeed an ape and not part of our lineage. The species evolved its unusual traits because of its unusual environment. Nine million years ago, during the Miocene epoch, the world’s climate was warmer and apes lived throughout much of Europe. The region of Italy where Oreopithecus was found was a swampy island at the time. Animals on islands often evolve unusual traits. (Scientists think the hobbit, Homo floresiensis, was exceptionally small because it lived on an island.) Oreopithecus lived in a place that lacked predators, so it was safer for the ape to travel on the ground. Waking upright, rather than climbing and swinging through the trees, also saved the ape energy, the researchers suggested. But the island was far from being a Shangri-La. The confined space meant food was limited and competition was fierce. Walking upright and precise manipulative abilities may have increased the ape’s foraging efficiency.

This view of Oreopithecus was not universally accepted. Other paleoanthropologists, such as Randall Susman of Stony Brook University in New York, interpreted the fossils differently. Where Köhler and Moyà-Solà saw human traits, Susman saw typical ape characteristics, such as long arms, short legs and curved toes, features associated with tree climbing. Some studies have suggested Oreopithecus may have been similar to modern orangutans. Susman also noted the Oreopithecus fossils are poorly preserved, and some of the bones are crushed, making it difficult to draw definitive conclusions.

Researchers have yet to find additional Oreopithecus fossils, so the debate remains in a stalemate. And Oreopithecus continues to be the most enigmatic ape of the Miocene.

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