By Steve Drury First PUBLISHED ON December 3, 2021
In 2015 the remains of about 15 hominins, new to science, were found in a near-inaccessible South African cave (See: The ‘star’ hominin of South Africa; September 2015), that number having risen to more than 24 at the time of writing.
The ‘star’ status of Homo naledi (named after the cave’s name Naledi meaning star in the local Sotho language) arose partly from an extraordinary barrage of promotion by the organisers of the expedition that unearthed them (probably to boost fundraising). But it was indeed one of the most extraordinary discoveries in palaeoanthropology.
The remains were recovered by a team of women archaeologists who small and lithe enough to wriggle through a maze of extremely narrow cave passages. The bones in the remote chamber were complete, with no sign of physical trauma, except gnawing by snails and beetles.
Few hominin fossils were found in the more accessible parts of the cave. One likely explanation was that a living H. naledi group had deliberately carried the bodies through the cave system for burial – at less than 1.5 m tall with a slender build they could have done this far more easily than the modern excavators.
A plausible alternative is that a group of H. naledi scrambled deep into the cave on being panicked by large predators, and suffocated as CO2 built-up to toxic levels.
Initially, the bones were estimated to be 2 Ma old. The fossils are so well-preserved that most aspects of their functional anatomy are known in great detail, such as the articulation of their hands and feet. Although not a single tool was found in the cave deposit, to get into the far reaches of the labyrinthine cave system they must have lit the way with firebrands.
The anatomy of H. naledi is far more advanced than that of contemporary H. habilis. The discoverers speculated that the group may have been a species that gave direct rise to the later H. ergaster and erectus, and ultimately us. Alternatively, the individuals’ diminutive size suggested parallels with much later H. floresiensis and H. luzonensis from the other side of the world. Much of this hype was later blunted by more reliable geochronology indicating an age of between 236 ka and 335 ka: i.e. about the time when anatomically modern humans were already roaming Africa. A more plausible conclusion, therefore, is that H. naledi was one of at least 6 hominin groups that co-occupied the late-Pleistocene world: i.e. similar to H. floresiensis.
Now the partial skull and half a dozen teeth of an immature H. naledi has been recovered from another remote chamber in the cave system (Brophy, J.K. et al. 2021. Immature Hominin Craniodental Remains From a New Locality in the Rising Star Cave System, South Africa. PaleoAnthropology. Issue 1.64; DOI: 10.48738/2021.iss1.64).
Fossils of young humans are rare, their bones being thinner and much more fragile than those of adults, so the skull had to be reconstructed from 28 fragments. Unlike the older individuals from the main chamber, there are no other bones associated with the skull. Oddly, the supposedly young H. naledi’s brain volume (between 480 to 610 cm3) is between 90 to 95 % that of adults. A possible explanation for this degree of similarity is that these beings reached maturity far more quickly than do anatomically modern humans. The evidence for youth is based on close dental similarity with those of other ‘immature’ specimens from the main bone deposit, and most importantly that two of the teeth are deemed to be deciduous (‘milk’) teeth. Yet the ‘milk’ teeth show severely chipped enamel as do the permanent teeth of more mature specimens, to the extent of being unique in the fossil record of hominins. Clearly, their diet was sand-rich.
Shortly after publication in the journal PaleoAnthropology during early November 2021 the world’s media leapt on the two papers reporting these new finds. Yet it is hard to judge why it was deemed by science journalists to have truly popular appeal. It actually adds very little to the H. naledi story, apart from specialised anatomical description. Despite the skull being bereft of the rest of the individual’s body, the authors ‘…regard it as likely that some hominin agency was involved in the deposition of the cranial material’. Perhaps the ‘star’ status was rekindled because the press release from the University of the Witwatersrand used the word ‘child’ again and again – a sure fire way of getting wide attention. The published papers properly refers to it as an ‘immature hominin individual’, which it undoubtedly is.
The same sort of attention came the way of Raymond Dart from a small skull of Australopithecus africanus found in 1924 by workers in a limestone quarry – he called it ‘the Taung Child’. Of course, H. naledi is one of the best-preserved hominins known. But how does its current newsworthiness rank above H. floresiensis? Now, that was a surprise, but the hype about that tiny human has died down. And when H. naledi was originally deemed to be 2 Ma old, it too was astonishing. But since its true, quite young age was determined, it too is no longer such a big deal.
Interestingly, South African scientists self-proclaimed the name ‘Cradle of Humankind’ for the area in Gautung Province close to Johannesburg, which is rich in limestone caves and has a long history of fossil hominin discoveries since Raymond Dart’s Taung Child. But the earliest anatomically modern human remains are from Jebel Irhoud in Morocco, and the oldest known hominin fossils are from Chad, and most advances in early hominin evolution have stemmed from Ethiopia, Kenya and Tanzania. The fossiliferous part of Gautung Province rightly has World Heritage status, but not under that name. Instead it is called more accurately ‘Fossil Hominid Sites of South Africa”
See also: Partial skull of a child of Homo naledi: Insight into stages of life of remarkable species. Science Daily, November 2021.
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Many thanks to Steve Drury for permission to republish his article and to Bernie Bell for sending it into The Orkney News.