Homo Naledi: Ancient Human Relative Walked Upright and Swung From Trees

Homo naledi hand and foot
The hand and foot of Homo naledi, a potentially-ancient human relative, show remarkable similarities to modern humans, according to two new studies. University of the Witwatersrand

Homo naledi, the ancient human relative recently discovered in South Africa, walked upright and climbed trees, according to new research.

Fossils belonging to H. naledi were first found at the Cradle of Humankind World Heritage Site, about 50 31 miles northwest of Johannesburg in South Africa, in October 2013. The researchers behind the find—the biggest single discovery of human fossils ever in Africa—believe that the hominid could be the most ancient member of the Homo genus to which modern humans belong, saying that it lived around three million years ago. However, a firm date has not yet been established.

Two new papers, published on Tuesday in the scientific journal Nature Communications, detail the remarkable similarities found between the bones of modern humans and the nearly 15 full H. naledi skeletons that have been discovered to date.

One study assessed 107 foot fossils, including a well-preserved adult right foot, and the other look at nearly 150 hand bones. The first study found that the ancient hominid had a bulky heel and short, straight toes that lay close together, similar to modern Homo sapiens. "We are seeing what's essentially a human foot," says Bernhard Zipfel, senior collections curator at the Evolutionary Studies Institute at the University of the Witwatersrand and co-author of the study. "There's very little about these feet that distinguish it from a modern human foot, but what makes it exciting is that these rather human feet are attached to [what is] very much a non-human hominid." Zipfel was also part of the team that confirmed the initial discovery of H. naledi.

But similar feet don't necessarily make for similar walking styles. Zipfel explains that more primitive features of H. naledi higher up the body—including at the hip and shoulder regions—suggest that the hominid would have been "a little more flat-footed than the average human."

Homo naledi
The cranium (A and B) and jaws of Homo naledi, which could be the oldest ancestor to modern Homo sapiens yet discovered. John Hawks/eLife

The second study, which focused on H. naledi's hand, found a unique mixture of features not seen before in other hominids. H. naledi had a wrist and palm similar to Neanderthals and H. sapiens that suggests an ability to manipulate tools, but the hominid also had finger bones (phalanges) that are even more curved than early fossils such as Lucy, the 3.2 million-year-old Australopithecus afarensis discovered in Ethiopia in 1974. The curved phalanges indicate that H. naledi still used their hands for climbing trees and that moving through the tree canopy may have been a secondary form of locomotion for the hominids, perhaps for when bipedal walking was impractical.

According to Zipfel, the confirmation that H. naledi was an upright, walking hominid is significant for understanding how the human brain developed. The brain of H. naledi was likely one-third of the size of a modern human brain, says Zipfel, suggesting that it was only once human-like creatures began to stand upright that they developed the high levels of intelligence seen in modern humans.

"It seems that we had to get up on our hind legs first [and] free up our hands so that we could start using our hands to develop technologies and through developing these technologies [such as bone and stone tools]... we would then subsequently develop a larger brain," says Zipfel.