Monday, 14 September 2015

A New Member Of Our Genus

During the 1970s when researchers cast fresh eyes over the Burgess Shale fossils, they discovered a multitude of new species. The names and classifications came so thick and fast that at one point Harry Whittington, the lead researcher, famously exclaimed 'oh fuck not another new phylum'. While Whittington's words were directed at the plethora of species from the Burgess Shale, for me they have become equally applicable to the fossils of early hominids. The fossil record of hominins in the last hundred years, has been transformed from a clear and orderly progression of forms, to a tangled web of hotly contended relationships spanning seven million years of geological history.

Cramped conditions inside the Dinaledi chamber
And now a new fossil, from the Dinaledi chamber of the Rising Star cave system in South Africa close to a series of other famous hominin sites, including Swartkrans, Sterkfontein and Kromdraai, is set to take centre stage.

The Dinaledi chamber and the first specimens, were discovered in 2013 when two cavers encountered a 20 centimetre wide, 12 metre long shaft branching off the preceding chamber.

Out of gruelling work conditions in 99% humidity came one of the richest collections of early hominin bones yet discovered. 15 individuals offered plenty of material to classify. The specimens lay within the genus Homo, but constituted a new species which researchers dubbed Homo naledi.

'It's got a tiny head and ape-like body, but arms and legs that are very human-like, something completely unexpected and we found it in incredible abundance,' said Lee Berger from the University of Witwatersrand. Berger's interpretations are controversial, in particular his proposition that the specimen's location in a cave represented an act of burial.

The impressive collection of specimens of Homo nadeli
Virtually all the bones in the caves came from the new species and the specimens themselves bore no signs of predation, suggesting that they had been placed in the cave deliberately. Such behaviours are unrecorded in other hominin species with a comparable cranial capacity.

Additionally, its age makes it difficult to place precisely within the hominin family tree, although current figures suggest that the fossils are no more than three million years old.

Determining its precise age will be important in determining whether it was ancestral to a contemporary, or descendant, of Homo habilis its closest relative both temporally and phylogenetically.

'I'm respectful of the material they found and I'm respectful of the efforts they made to recover it, but I'm extremely sceptical about the interpretation of them,' said palaeoanthropologist Bernard Wood. Further study, particularly of the age of Homo nadeli, is needed before its precise place in hominin history can be established. Only then can theories regarding mental capacity be accurately assessed. Nevertheless, Homo nadeli represents an intriguing addition to the family tree.