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September 18, 2015

A few years ago in South Africa spelunkers were exploring a cave near Johannesburg. Working their way through a series of smaller and larger spaces, they found themselves in a small chamber with a scattering of bones on the surface.  Thus began an intriguing search to discover the nature and significance of these bones.

Dr Lee Berger of the University of Witwatersrand became involved, determined the bones were hominin and mustered a team to investigate the remains The cave was named Rising Star and last week an announcement was made in the online journal eLife by Berger and his team that the bones represented an early species in the genus Homo.

There appear to be many hundreds of bones, many still unexcavated and comprising perhaps as many as 15 hominin individuals.. There is a major difficulty with this find: it cannot be dated. Often in East Africa, fossil hominids can be dated if strata of volcanic ash are found interlaced with other sedimentary layers. When fossils are found in South African caves, as in this case, a date can be established, sometimes, if the hominid remains are accompanied by the fossilized remains of other animals for whom clear dating has been established. In the Rising Star cave, no volcanic ash has penetrated and neither are there the remains of other animals. Nor are there artifacts such as stone tools.

Comparisons can be made with hominin bones found elsewhere. Brain size and teeth can be indicative. With regard to the Rising Star fossils, some researchers - and Donald Johanson, who discovered Lucy, is one - posit the Rising Star fossils correspond most closely to Homo erectus, a species widespread throughout the Old World and existing between two million and 50,000 years ago. Berger et al. however discern unique features and have name their collection a new species, Homo naledi.