The discovery of a new human-related species, named Homo naledi, has thrown the evolutionary biology world for a loop. The newfound species, uncovered in a South African cave system, appears to be an odd combination of primitive and modern features not previously seen together.
From the remains of at least 15 individuals, scientists assembled the skeletal system of Homo naledi and published the findings in the journal eLife. The new species has some remarkably human-like similarities, namely its hands and feet—though its brain is much smaller, as is its frame. Human hands have played a key role in the evolution of Homo sapiens, and that’s one of the similarities between humans and Homo naledi. Individuals of the Homo naledi species had opposable thumbs much like our own that would have allowed them dexterity somewhat like that of humans. The curved nature of the hands also suggests that the species may have had climbing abilities. Many of our close ancestors, including chimpanzees and apes, have opposable thumbs.
Perhaps the most significant similarity is not anatomical. Scientists say the cave location the Homo naledi remains were found appears to be a burial chamber. Burying the dead was a practice previously thought to be a unique human trait.
These similarities carry significance from an evolutionary perspective, but a number of traits make humans stand out from our predecessors. Human brains are typically between 1,100 and 1,200 cubic centimeters. Scientists estimated that the brain in Homo naledi would have been about half that size. Brain size isn’t everything when it comes to intelligent life and evolution, of course, but the structure of the brain in Homo naledi, revealed by the shape of the skull, also suggests a more primitive brain. Together, when comparing humans to a direct ancestor, the brain does suggest some distance between humans and Homo naledi.
The frame, including the shoulders and pelvis, also bears closer resemblance to early hominin species. Overall, scientists believe Homo naledi individuals weigh less than their human counterparts.
The differences between humans and Homo naledi are significant, but that doesn’t diminish the significance of the finding. The discovery of a human-related species just underscores how little we know about the lifeforms the preceded ours’ millions of years ago.