335,000 to 236,000 years ago

Image credit Witwatersrand University

Homo naledi is an extinct hominin species (“naledi” meaning “star” in the language Sotho) known from an extensive assemblage of bones found in Malapa, in the Rising Star Cave system in South Africa. While the original publication of the material posited an age of 1.0 to 2.0 million years old, more recent dating attempts have assigned a younger date of around 335,000 to 236,000 years old. The extensive assemblage is comprised of the fragmentary remains of at least 15 different individuals of the species, including both juveniles and adults.

In terms of the anatomy, like many other hominin species it is characterized by a mosaic pattern of ancestral and derived traits. Homo naledi was bipedal, with many Homolike modifications of the skeleton to support a more human-like mode of locomotion, relative to older hominins such as those in the genus Australopithecus. Interestingly, while many features of the legs and wrist joint are more Homo-like, the fingers of H. naledi are longer than most other hominin species. The proximal phalanges, the finger bones closest to the hand, are also curved, more than is seen even in some australopiths. Its feet also show some ape-like features. These traits suggest a capacity for arboreal locomotion—in particular, climbing, or arboreal suspension (i.e., hanging from tree branches).

On average, H. naledi specimens stood just under five feet tall, around 4 foot 9 inches on average. The estimated cranial capacity (which measures the volume of the inside of the brain case) ranges between 465 to 610 cubic centimeters (cc), which is much smaller than the average for humans (about 1300 cc). Even relative to their small body size, the H. naledi brain is small and demonstrates the persistence of small-brained hominins late in the human evolutionary timeline. The shape of the skull is Homolike, and while the size of the teeth is similar to other Pleistocene hominins, many of the traits (or lack thereof, in the case of many dental features seen in modern humans) are more Australopithecus afarensis– or Paranthropus-like.

There are still unanswered questions about this species. The phylogenetic relationship of Homo naledi to other hominin species is still unknown. Homo naledi possesses a unique suite of both Australopithecuslike and Homolike characteristics that make determining its precise relationship with other species difficult. Additionally, both ancestral and contemporaneous species of hominins were manufacturing stone tools. To date, no stone tools have been reported from the site, so it is unclear what the technological capacity of the species was. Further, there are still some unsettled debates about whether H. naledi buried their dead, with continued arguments for and against. Research into the paleobiology of H. naledi is ongoing and dynamic, and the excavations at the Rising Star cave system have continued. Ongoing analysis of the existing fossils and the discovery of new material will continue to reveal new, fascinating information about this species.

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