Homo naledi: The Star Man Rewriting Our Origins

In September 2015, the world of paleontology was shaken by a stunning announcement: the discovery, in an almost inaccessible cave in South AfricaAfricaThe cradle of humankind: the continent where the first hominins appeared, then Homo sapiens around 300,000 years ago, before the expansion to the rest of the world.→, of fossil remains belonging to a completely unknown human species. Homo naledi, the Star Man, combines anatomical traits that defy simple classification and raises fundamental questions about the diversity and behaviors of PleistocenePleistoceneThe geological epoch of the great ice ages (c. 2.6 Ma–11,700 BP), spanning most of human prehistory.→ hominins. Its dating, revealed two years later, places it among the contemporaries of our own species, making its significance even more disturbing.

The Star Cave: A Spectacular Discovery

The story of Homo naledi begins in 2013, when two South African amateur cavers, Rick Hunter and Steven Tucker, were exploring the Rising Star cave system, about 50 km northwest of Johannesburg, in the Cradle of Humankind region - a UNESCO World Heritage Site. While searching for new passages, they squeezed through a fissure no wider than 18 cm, descended a near-vertical conduit, and emerged in a completely isolated chamber carpeted with fossils¹.

They contacted paleontologist Lee Berger of the University of the Witwatersrand, who - unable to pass through the narrow passages himself - organized a global call to recruit small scientists capable of entering the cave. Six female scientists, nicknamed "underground astronauts", formed the excavation team and worked for three weeks in the Dinaledi Chamber, recovering fossils. The results exceeded all expectations: more than 1,550 specimens representing at least 15 different individuals, of all ages, were recovered.

The official announcement was made in September 2015 in the journal eLife in two simultaneously published papers describing the anatomy of the species and the circumstances of the discovery². The name "naledi" means "star" in Sesotho, a southern African language, in reference to the name of the cave.

A Paradoxical Anatomy: A Unique Mix of Primitive and Advanced Traits

Homo naledi presents one of the most perplexing anatomical combinations ever seen in a homininHomininMember of the subtribe Hominina, comprising the human lineage (Homo, Australopithecus, Paranthropus…) but excluding orangutans and gibbons. The term progressively replaces "hominid" in its narrow sense.→. Its brain is remarkably small: between 465 and 610 cm³, a value close to that of australopiths and Homo habilis, far below that of Homo erectus or Homo heidelbergensisHomo heidelbergensisMiddle Pleistocene human species, often seen as the common ancestor of Neanderthals and our own species.→. Its body size is also modest: approximately 150 cm tall and 45 kg, values similar to those of early Homo³.

But other aspects of its anatomy are markedly more advanced. Naledi's feet are almost identical to those of Homo sapiensHomo sapiensThe present-day human species, which emerged in Africa around 300,000 years ago, the only surviving human lineage after the extinction of Neanderthals and Denisovans.→, indicating highly efficient bipedal walking. The hands are striking: the phalanges are strongly curved, as in arboreal species, yet the thumb is robust and the carpal joints are compatible with tool use. The shoulders, however, are oriented upward and forward, like those of great apesgreat apesThe family of great apes (Hominidae) comprising orangutans, gorillas, chimpanzees, bonobos and humans.→ - morphology adapted for climbing.

Naledi's dentition is small and modern in shape, with relatively modest crown volume - very different from the massive teeth of robust australopiths. The deciduous teeth resemble those of early Homo, but the permanent teeth have distinctive characteristics. The leg bones, particularly the femur and tibia, are gracile and elongated, typical of an efficient biped.

In summary, Homo naledi appears to be an evolutionary patchwork: a primitive small brain, a gracile body, hands adapted for both climbing and manipulation, and nearly modern feet. Some researchers have interpreted this as the result of evolution in isolation, perhaps in restricted populations.

The Astonishing Date: 335,000 Years Old

At the time of the 2015 announcement, dating remained a mystery due to difficulties applying standard radiometric methods in that context. The primitive skull morphology suggested an age of at least 2 million years. The answer, published in 2017 by Paul Dirks and colleagues, stunned the scientific community: specimens from the Dinaledi Chamber date between 335,000 and 226,000 years ago⁴.

This date means that Homo naledi was living in South Africa at the same time as Homo heidelbergensis, the earliest Homo sapiens in eastern Africa, and possibly the NeanderthalsNeanderthalsA fossil humanity of Eurasia, robust and cold-adapted, extinct around 40,000 years before present.→ in Europe. A hominin with a brain as small as Homo habilis was therefore coexisting with our own direct ancestor, in the same part of the world. This challenges the idea that human evolution was a linear process of progressive replacement of one species by a more advanced one.

Also in 2017, a second chamber in the cave system, the Lesedi Chamber, yielded remains of at least three more individuals, including a nearly complete adult male nicknamed "Neo". This specimen, with a partially intact skull with a cranial capacity of about 610 cm³, allowed refinement of the cranial anatomy reconstruction for the species.

The Mystery of Deliberate BurialBurialThe intentional deposition of a body, sometimes with offerings; a marker of symbolic behaviour.→

The most intriguing question posed by Homo naledi may be how its remains ended up in the Dinaledi Chamber. Access required passing through a 12-meter vertical narrow chute followed by a horizontal fissure less than 20 cm wide. It is nearly impossible that a predator transported bodies there, or that individuals wandered in alone and died accidentally.

The most parsimonious conclusion, advanced by Lee Berger and his team, is that naledi deliberately deposited its dead in this chamber - a behavior implying advanced social cognition, perhaps even an awareness of death⁵. This funerary or proto-funerary behavior would be the oldest ever documented, and for a species with a much smaller brain than our own. The scientific community remains divided on this interpretation: other mechanisms, such as gradual deposition over time or the existence of an ancient passage now blocked, have been proposed.

In 2023, Lee Berger and his team announced even more provocative findings: traces of fire in the Rising Star caves and what appears to be deliberate engravings on the walls. If confirmed, these observations would further support the hypothesis of advanced cognition in naledi, though these highly contested claims continue to generate intense debate.

Naledi's Place in Human Evolution

Homo naledi represents a challenge to simplistic models of human evolution. Its primitive brain and mosaic morphologyMosaic morphologyThe combination, in a single organism, of primitive and derived anatomical traits, as if the body assembled parts of different ages.→ suggest either that it descends from a very ancient lineage that remained isolated, or that it represents a species that evolved independently in southern Africa. Its coexistence with hominins of much larger brains raises questions about competition and interaction between human species in mid-Pleistocene Africa.

Genetic analyses have so far not been conducted on naledi specimens, as the cave conditions, while favorable for bone preservation, are not ideal for ancient DNAAncient DNAGenetic material preserved in old remains, often degraded, sequenced with cutting-edge techniques.→ preservation. The phylogenetic position of the species therefore rests entirely on morphological data, which alone cannot settle the question definitively.

Homo naledi reminds us that sub-Saharan AfricaSub-Saharan AfricaThe part of Africa south of the Sahara; cradle of Homo sapiens, long thought hostile to ancient-DNA preservation because of heat.→, less thoroughly prospected than some other regions, still holds immense surprises. It profoundly changes our vision of human evolution in Africa as a simple, linear process, and opens the way for future research that promises equally groundbreaking discoveries.