Human Relative’s Foot a Step Towards Modern Walking

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A new study of Homo naledi, the extinct human relative whose remains were discovered in a South African cave and introduced to the world in the October Issue of National Geographic, suggests that although its feet were the most human-like part of its body, H. naledi didn’t use them to walk in the same way we do. Detailed analysis of 107 foot bones indicates that H. naledi was well adapted for standing and walking on two feet, but that it also was likely comfortable climbing trees. That’s the conclusion of work published today in the journal Nature Communications.

H Naledi Foot
A digital reconstruction of the fossilized foot of human relative Homo naledi.
© Nature Communications

Homo naledi’s foot is far more advanced than other parts of its body, for instance, its shoulders, skull, or pelvis,” said William Harcourt-Smith, lead author of the new paper and a resident research associate in the American Museum of Natural History’s Division of Paleontology, and assistant professor at CUNY’s Lehman College. “Quite obviously, having a very human-like foot was advantageous to this creature because it was the foot that lost its primitive, or ape-like, features first.”

Walking upright is one of the defining features of the human lineage, and as feet are the only structure that make contact with the ground in bipeds, they can tell us a lot about our ancient relatives’ way of moving. In the Dinaledi Chamber of the Rising Star cave system in South Africa, the H. naledi excavation team recovered at least one specimen from almost every single bone in the new species’ foot.

H Naledi Foot Nat Geo
The foot of Homo naledi is astonishingly humanlike. Only a few traits, such as slightly more curved toe bones, retain a primitive cast. 
Art: Stefan Fichtel. Sources: Lee Berger and Peter Schmid, Wits; John Hawks, University of Wisconsin-Madison/National Geographic

Analysis of these bones has shown that the foot bones look much more like human bones than chimpanzee bones, except for two major areas: the toes of H. naledi’s foot were more curved and their feet were generally flatter than seen in the average modern human. Taken alongside clues from other parts of its body—like its long, curved fingers, and ape-like shoulder joint—a picture emerges of a creature that was undoubtedly bipedal but also a tree climber.

Since we don’t yet know the age of the H. naledi fossils, researchers don’t know how this form of bipedalism fits into the hominin family tree.

“Regardless of age, this species is going to cause a paradigm shift in the way we think about human evolution, not only in the behavioral implications—which are fascinating—but in morphological and anatomical terms,” Harcourt-Smith said.