The discovery of Homo naledi, an extinct hominin species, has introduced fascinating questions to the study of human evolution. Unveiled in 2015, this ancient relative was found in a South African cave system. The large collection of fossils belongs to a previously unknown species, prompting scientists to re-examine the timeline of hominin existence and the development of complex behaviors. The unique circumstances of the discovery and its unusual physical traits have made Homo naledi a subject of intense scientific interest.
The Rising Star Cave Discovery
The story of Homo naledi began deep within the Rising Star cave system, located in the Cradle of Humankind World Heritage Site in South Africa. In 2013, recreational cavers Rick Hunter and Steven Tucker entered a previously unexplored chamber and found the floor littered with bones. They reported the find to paleoanthropologist Lee Berger, who organized an excavation of the exceptionally difficult-to-access site, named the Dinaledi Chamber.
Berger assembled a team of slender excavators with caving and archaeological experience, often called the “Underground Astronauts,” to systematically excavate the chamber. Over two expeditions in 2013 and 2014, they recovered more than 1,550 fossil specimens belonging to at least 15 individuals. A second chamber, the Lesedi Chamber, was later explored, yielding more remains of the species.
Physical Anatomy and Traits
Homo naledi presents a mosaic of physical features, combining traits seen in more ancient hominins with those of the genus Homo. One of the most striking features is its small braincase. The estimated cranial capacity is between 465 and 610 cubic centimeters, which is closer to that of an australopithecine and about a third of the size of a modern human’s brain. This small brain size contrasts sharply with other physical attributes that appear much more modern.
The species had hands and feet that were remarkably human-like in their structure. The wrist and palm bones suggest a powerful grip and the ability for fine manipulation, similar to later hominins. The feet were adapted for walking upright, with arches and a big toe aligned with the other toes, indicating an efficient, bipedal stride. However, the fingers were long and curved, a primitive trait often associated with climbing abilities.
This combination of features extends throughout the skeleton. The shoulders were configured in a way that would have been advantageous for climbing, similar to earlier hominins. Yet, the leg bones were long and slender, much like those of early Homo species built for long-distance walking. The vertebrae and ribcage also showed a mix of primitive and more derived characteristics.
Placement in the Hominin Timeline
Initially, the primitive aspects of Homo naledi’s anatomy led some researchers to believe the fossils were much older. However, direct dating of the fossil material and surrounding sediments produced a surprising result. The remains from the Dinaledi Chamber were found to be between 335,000 and 236,000 years old, placing Homo naledi in the Middle Pleistocene epoch.
This recent age is significant because it means Homo naledi was a contemporary of early Homo sapiens in Africa. For a long time, it was thought that by this period, larger-brained hominins had outcompeted and replaced their smaller-brained relatives. The existence of a small-brained hominin species living alongside anatomically modern humans challenges previous assumptions about the linear progression of human evolution.
Evidence of Complex Behaviors
The location and context of the fossil discoveries have led to profound claims about Homo naledi’s cognitive abilities. The primary hypothesis is that the individuals were intentionally placed in the deep, dark chambers of the cave. This argument is based on the number of individuals found, the absence of signs of predation, and no indication that water washed the bones into the cave. If this was deliberate body disposal, it would represent a behavior previously thought exclusive to larger-brained species.
The discovery team has also reported finding evidence of controlled fire use within the passages, suggesting Homo naledi may have used fire for light to navigate the pitch-black cave system. Remnants of charcoal and burned animal bones were identified in areas near the fossil deposits, though these claims are still undergoing intense scientific scrutiny.
Another debated claim is the discovery of what appear to be abstract engravings on the cave walls near the fossil chambers. These markings include cross-hatch patterns and geometric shapes. These proposals—intentional burial, the use of fire, and the creation of art—suggest a level of cognitive complexity unexpected for a hominin with such a small brain, and all claims remain subjects of active debate.