Miocene ape inner ear fossil sheds light on bipedalism origin

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News Team

A recent study on the fossil of a Lufengpithecus, an ancient ape that lived in China around 7 to 8 million years ago, has provided new information on the evolution of human bipedalism. The study, published in The Innovation, was conducted by a team from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences, the Yunnan Institute of Cultural Relics and Archeology (YICRA), and New York University (NYU).

Humans and apes have different ways of moving, from walking upright on two legs to climbing trees or walking on all fours. Scientists have been trying to understand how our unique bipedal posture and movements evolved from an ancestor that walked on all fours. Most studies on the evolution of ape locomotion have focused on the bones of the limbs, shoulders, pelvis, and spine, but this study used a new approach focusing on the study of the inner ear.

The semicircular canals, located in the skull between our brain and external ear, are fundamental to our sense of balance and position when we move. They provide a fundamental component of our locomotion that most people are probably unaware of. Thanks to modern imaging techniques, researchers were able to visualize the internal structure of skull fossils and study the anatomical details of the semicircular canals to reveal how extinct mammals moved.

Lufengpithecus, slightly smaller than a chimpanzee, lived in the Miocene, between 6.2 and 12.5 million years ago, in present-day Yunnan province in southwestern China. The fossil record of Lufengpithecus includes fossil bones of the skeleton and some skulls, but since they were compressed, they prevented researchers from seeing the ear region, which could never be studied. Now, thanks to an advanced multi-scale and multi-modal 3D imaging system, the team has managed to see the inner ear and its bony semicircular canals and create an accurate virtual reconstruction of the delicate structures of the bony canals.

Comparing them with those of other living and fossil apes and humans from Asia, Europe, and Africa, they discovered that the first apes shared a locomotor repertoire that was the ancestor of human bipedalism. The human lineage then diverged from the great apes and opted for bipedalism, as observed in Australopithecus, a primitive human relative from Africa.

The researchers believe that the planet’s colder temperatures, starting about 3.2 million years ago, may have been an important environmental catalyst in which apes and humans diversified their locomotor function. “Our study points to an evolution of bipedalism human development in three stages: In the first, the first apes moved through the trees in a style very similar to aspects of the way gibbons do today in Asia,” explains co-author Terry Harrison of the University of New York. “In the second, the last common ancestor of apes and humans had a locomotor repertoire similar to that of Lufengpithecus, which combined climbing and climbing, suspension of the forelimbs, bipedalism, and quadrupedism. From this extensive locomotor repertoire ancestral human bipedalism evolved”, (the third stage).

Image Source: www.infobae.com

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