Artist’s reconstruction of the burial of an adult Homo naledi found in the Dinaledi Chamber. Credit: Berger et al., 2023
Forensic anthropologists working in the famous Rising Star cave system in South Africa have found evidence of ancient human burials that predate the earliest currently known Homo sapiens’ burials by at least 100,000 years.
In their search to understand human origins, the team of forensic anthropologists and explores identified depressions deep in the chambers of the Rising Star cave system. Bodies of Homo naledi adults and several children, estimated to be younger than 13 years of age, were deposited in fetal positions within pits, which suggests intentional burial of the dead. The Homo naledi fossils have been dated to around 226,000–335,000 years old.
Small-brained ancestors
Homo naledi, an extinct human ancestor, were first discovered in 2013 inside the Rising Star cave system 25 miles northwest of Johannesburg. The species is characterized by its small size, most notably a brain roughly a third the size of modern humans. However, the species boasts a number of relatively modern anatomical features that perplex anthropologists to this day.
The skeletal remains are dated to a period when modern humans were just beginning to emerge in Africa. They were discovered in a single, hard-to-reach subsystem within the Rising Star cave system.
The team, which is led by researchers from the University of the Witwatersrand (South Africa), first raised the possibility of intentional burials in 2015. However, many were—and still are—skeptical that a small-brained hominin could engage in such human-like funerary behavior.
Now the latest findings, published in three papers across the pre-print publication bioRxiv, provide strong evidence to the contrary.
Orientation and stratigraphy
While there are multiple lines of evidence supporting intentional burials, the team places focus on two specific elements found in the Dinaledi Feature and the Hill Antechamber Feature—the position of the bodies and the stratigraphy of the cave floors.
Throughout the cave, skeletal remains were recovered from vertical shallow pits that cut through the layers of the cave floor, in opposition to its natural slope. The researchers say the vertical orientation of the remains is reflective of decomposition with matrix support. For example, in the Dinaledi Feature, a portion of ribcage is visible with some ribs oriented near vertical, others broken and collapsing, but all constrained by support along the edge of the pit feature. Additionally, cranial fragments were found near the south end of the pit, also supported by matrix in a vertical arrangement.
In the Hill Antechamber Feature, the research team excavated a minimum of 90 skeletal elements and 51 dental elements. CT scans revealed the remains to be of at least three individuals, including an older juvenile. The youth’s remains appear undisturbed and intact, including 30 teeth in the correct order, two series of partial ribs, a right foot, ankle, and lower limb bones. The team says this pattern of bones is consistent with a body curled up in the fetal position for burial.
Additionally, according to the study, there are differences in the sediment of the pits compared with the surrounding walls and cave floor. The floor of the Hill Antechamber is a steep slope of approximately 30 degrees and composed of orange-red mud clasts, much like the Dinaledi Chamber. The excavation profiles at the east and south edges of the feature show distinct layering of orange-red mud clasts parallel to the chamber floor. But CT data shows these layers are interrupted.
A bowl-shaped concave layer of clasts and sediment-free voids makes up the bottom of the Hill Antechamber, while the south end slopes in the opposite direction as the chamber floor. The older juvenile’s right foot and lower limb is supported by this concave layer. Above the foot is additional sediment infill, separating it from the upper limb and torso material.
“The texture and internal stratigraphy of this sediment infill is not compatible with slow incremental deposition or the percolation of small particles around and into skeletal remains that were once exposed on the antechamber floor. The combination of these lines of evidence indicates that a pit was dug into existing strata, and then a body was placed into it and buried prior to the decomposition of soft tissue,” write the researchers in their paper.
The research team believes these interments, along with other evidence, suggest intentional burials were conducted by H. naledi within the cave system, and mortuary practices are not limited to hominins with large brain sizes.
“The evidence demonstrates that this complex cultural behavior was not a simple function of brain size,” the team concludes. “This raises the possibility that burial or other mortuary behavior may have arisen much earlier than present evidence for them, or that such behaviors evolved convergently in minds different from our own. Understanding such behaviors will require comparative study of all hominin lineages in which they occur.”