Since Homo naledi was presented in 2015 [see related article], a global project has been carried out with 150+ scientists involved in the analysis of the anatomy, behavior, diet, geology and chronology, but also a massive exploration project in the field, inside the Rising Star cave system and other cave systems in the area.

The result is astonishing: this project has yielded more hominin fossils in the last 3 years than in the rest of history in Africa. And the exploration is far from finished: this will surely be followed by a number of further projects and discoveries in the following years.

Back in 2015, it was announced the Dinaledi chamber of the Rising Star cave, containing 1500+ hominin remains corresponding to 15 individuals of Homo naledi, which became one of the most famous species. But thousands of other remains were there still to be discovered and analysed.

Reconstruction of Homo naledi. Photo: Lee R. Berger

A pending question: What was the place of Homo naledi in the evolutionary tree?

The dating of Homo naledi could not be realized by then. In the last two years, geochronologists from 11 laboratories around the world have determined that the Homo naledi remains from Dinaledi are 241-335 K years old. And this is really surprising because its anatomy is rude and primitive, corresponding actually to M’s years rather than K’s years. And clearly it is, because the species has likely its origin M’s years ago, close to the roots of the Homo genus.

Such recent dating makes very possible that Homo naledi encountered Homo sapiens, or other archaic forms of Homo sapiens. If naledi groups were in competition for resources and shared ecological areas with other humans, how could they survive? Let me remember that naledi’s brain is tiny (c. 500 cc), only a bit bigger than the brain size of a modern chimp (c. 350 cc) and far from modern humans (c. 1200 cc).

In other case, how could naledi groups survive in extreme isolation during thousands of years of evolution? We can easily think of the comparable Homo floresiensis case, but this was truly isolated, physically.

A combination of different dating techniques were used: optically stimulated luminescence dating of sediments with U-Th dating and palaeomagnetic analyses of flowstones, plus direct dating of the teeth using U-series and ESR.

A controversial hypothesis: the bodies was disposed by purpose

Now the research team has studied a second site inside Rising Star, the Lesedi chamber (Lesedi means ‘light’ in the Setswana language), which is 100 meters away from the first Dinaledi chamber announced in 2015. Both chambers are equally difficult to get into there. The Lesedi chamber has yielded 130 new fossils, corresponding to 3 individuals, two adults and one child.

‘Neo’, Homo naledi sleleton. Credit: Hawks et al (2017) eLife

The quality of the fossil preservation is extraordinary. They show no cut marks, water remotion or signs from other animal activity. Both chambers are in complete darkness and have no evidence of regular habitation. How could these bones reach such place? Did the other group members dispose them there by purpose? Is there any alternative way to get those chambers, not found yet? We may find a similar complex behavior 430 Kya in Sima de los Huesos (Spain) but these hominins had c. 1000 cc brains. Are both cases comparable?

‘Neo’, the most complete skeleton of Homo naledi

Neo is a remarkably complete adult skeleton (probably male) of Homo naledi found at the Lesedi chamber, even more complete than the famous Lucy, considering the preserved cranium and the mandible. Neo means «a gift» in the Sesotho language. The Lesedi fossils have not been dated yet.

It has also provided the first complete face of this species!

‘Neo’, Homo naledi cranium. Credit: Hawks et al (2017) eLife

«The southern half of Africa was home to a diversity that we’ve never seen anywhere else», John Hawks

«At least two potential makers of the very complex stone industries… This is going to lead to perhaps a lot of more questions than answers», Lee Berger