About six million years ago, the lineage which would lead to the evolution of modern humans broke off from the lineage which would lead to the modern apes, such as the chimpanzee. The earliest ancestors to humans were distinguished by bipedalism—the ability to walk upright.
About 2.5 million years ago, the first Homo species evolved in Africa: Homo habilis made and used stone tools and had a somewhat larger brain than Australopithecus, the species from which Homo evolved. Over the next two million years there is physical evolution characterized by an increasing brain size and cultural evolution shown by an increasingly complex tool kit.
The process of human evolution has not been linear but has been a complex puzzle with many dead ends, with branches of Homo that are not directly ancestral to modern Homo sapiens and times when several species of Homo have lived on the planet together. One of the exciting things about paleoanthropology in the twenty-first century is that when we feel that we are close to understanding the evolution of our species, there are new discoveries from archaeology and genetics which change everything. One of these discoveries has come from the Rising Star Caves in South Africa.
The Rising Star Caves are difficult to access, yet in spite of this, some early humans crawled through the narrow passages and deposited dead bodies. Archaeologists have now recovered at least 1,550 bones from this site which suggest that at least 15 bodies were deposited here. The bones cover a range of ages, from the elderly to infants. There are examples of nearly every bone in the human body.
The finds of these early humans have been given the designation Homo naledi (naledi means star in the Sesotho language.) Anatomically, Homo naledi looks similar to early humans such as Homo habilis. This suggests that Homo naledi and Homo habilis may have had a common ancestor or that Homo habilis is ancestral to Homo naledi.
The skull of Homo naledi appears to be similar to that of early humans, but the brain size—560 cubic milliliters—is about half the size of that of modern humans.
The Oregon Museum of Science and Industry (OMSI) in Portland has a small display on Homo Naledi which features a 3-D printed skull which is shown below.
According to the display:
“Homo naledi have very similar bodies to early humans. However, they have small brains (about 1/3rd the size of ours), curved fingers for climbing and were only about 4 feet 10 inches and 100 pounds. It is possible that Homo naledi were found in caves because they ‘buried’ their dead there.”
The bodies were deliberately placed in the cave, and that meant working in the total absence of light which suggests that Homo naledi may have mastered the use of fire. As yet, however, there is no evidence that Homo naledi was making and using stone tools.
With regard to anatomy, James Shreeve, in a report in National Geographic, writes:
“A fully modern hand sported wackily curved fingers, fit for a creature climbing trees. The shoulders were apish too, and the widely flaring blades of the pelvis were as primitive as Lucy’s—but the bottom of the same pelvis looked like a modern human’s. The leg bones started out shaped like an australopithecine’s but gathered modernity as they descended to the ground. The feet were virtually indistinguishable from our own.”
The anatomical features, such as the curved fingers and the pelvis, initially suggested that Homo naledi should have flourished during the evolutionary transition from Australopithecus to Homo, that is, 2-3 million years ago. It was surprising, therefore, to find that the remains date to only 236,000 to 335,000 years ago. In a report in Skeptic, Nathan Lents writes:
“Based on the anatomical features, most agree that H. naledi is an early species of the Homo genus, so the tender young age of 300,000 years is quite a surprise.”
The lack of stone tools associated with Homo naledi may be an indication that the curved fingers on the hand made tool-making difficult or, just as likely, any stone tools which they made have not yet been identified at archaeological sites. At the present time, there are no habitation sites which have been clearly associated with Homo naledi.
The bodies in the Rising Star caves appear to have been deliberately placed there, and this raises another interesting question: did Homo naledi have beliefs about an afterlife? Burials are often seen as evidence for the earliest religions. Did Homo naledi have religion?
Homo naledi, like Homo floresiensis (“the hobbit”) and Homo altai (Denisovans) remind us that evolution is not a simple linear progression, but there are many branches which intertwine (crossbreed) and eventually go extinct.
More Ancient Ancestors
Ancient Humans: Fire
Early Homo Sapiens: A Brief Overview of DNA
Ancient Humans: Neandertal Language?
Ancient Africa: How Old Is It?
Ancient Africa: Early Homo Sapiens at Pinnacle Point
Ancient Humans: A Short Overview of Homo Ergaster
Ancient Africa: A Short Overview of Homo Habilis
The Ancient World: An Overview of Homo Erectus