How early humans learned to walk from an ancestor called Lufengpithecus

Humans and apes share a fascinating array of locomotive abilities, ranging from upright walking to tree climbing and four-limbed movement.

The transition from our quadrupedal ancestors to the bipedal posture unique to humans has long captivated scientists.

Despite extensive studies and fossil examinations, the early stages of this evolutionary journey remained largely obscured — until now.

A fascinating study, leveraging novel techniques and recent fossil discoveries, sheds new light on this mystery.

The inner ear of Lufengpithecus

At its core is the 6-million-year-old Lufengpithecus fossil, unearthed in China.

The research team, using advanced three-dimensional CT scanning, focused on a previously overlooked area: the bony inner ear region of these ancient skulls.

This approach has provided pivotal insights into the origins of bipedal locomotion.

Yinan Zhang, a doctoral student at the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) and lead author, explains the significance of this approach.

“The semicircular canals, located in the skull between our brains and the external ear, are critical to providing our sense of balance and position when we move, and they provide a fundamental component of our locomotion that most people are probably unaware of,” Zhang said.

Humans walking happened in three stages

Co-author Terry Harrison, a New York University anthropologist, outlines a three-step evolutionary process that led to humans walking on two feet, as revealed by the study.

Initially, early apes moved in trees, akin to modern-day gibbons. The last common ancestor of apes and humans, similar to Lufengpithecus, displayed a mixed locomotion pattern — climbing, suspension, arboreal bipedalism, and ground movement.

This diverse locomotor repertoire laid the foundation for human bipedalism.

Prior research often focused on limb, shoulder, pelvis, and spine bones to understand ape and human movement.

However, the variability in living ape locomotion and gaps in the fossil record have hindered a complete understanding of human bipedalism’s origins.

The Lufengpithecus skulls, discovered in the 1980s in Yunnan Province, China, offered a new avenue for investigation.

3D insights into ancient skulls

Earlier researchers, hindered by the skulls’ distorted state, overlooked the ear region. Zhang, Ni, Harrison, and their colleagues at IVPP and the Yunnan Institute of Cultural Relics and Archaeology (YICRA) utilized 3D scanning technology to reconstruct the inner ear’s bony canals virtually.

Comparing these reconstructions with data from other apes and humans, they unveiled a detailed picture of early ape locomotion.

Professor Xijun Ni of IVPP, who led the project, highlights the study’s unique contribution.

“Our analyses show that early apes shared a locomotor repertoire that was ancestral to human bipedalism,” explains Ni.

“It appears that the inner ear provides a unique record of the evolutionary history of ape locomotion that offers an invaluable alternative to the study of the postcranial skeleton.”

Environmental changes also led to humans walking

Ni adds that most fossil apes represent an intermediate locomotor mode between gibbons and African apes.

The human lineage diverged from great apes with the adoption of bipedalism, as evidenced in Australopithecus, an early human relative.

The team also proposed that climate change might have been a crucial factor in driving the locomotor diversification of apes and humans.

“Cooler global temperatures, associated with the build up of glacial ice sheets in the northern hemisphere approximately 3.2 million years ago, correspond with an uptick in the rate of change of the bony labyrinth and this may signal a rapid increase in the pace of ape and human locomotor evolution,” explains Harrison.

Deciphering our evolutionary bipedalism legacy

In summary, this study marks a pivotal advancement in understanding the evolutionary path of human bipedalism.

By innovatively analyzing the inner ear structure of the Lufengpithecus fossils through 3D CT scanning, the research team has shed light on the complex journey from arboreal locomotion to upright walking.

This discovery challenges previous assumptions in paleoanthropology while highlighting the intricate interplay between our physical evolution and environmental shifts.

As we continue to uncover these evolutionary mysteries, our comprehension of human origins becomes ever more nuanced, offering profound insights into the story of our species.

The full study was published in the journal The Innovation.

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