Researchers find age of South Africa’s ‘young’ hominid fossil

Published in the May 2017 issue

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Dr Renaud Joannes-Boyau holding one of Homo naledi’s teeth from the Rising Star cave system before undertaking US-ESR direct dating of the fossil in the University’s GARG laboratories.

The age of a hominid fossil found in South Africa, which has been dated using state-of-the art techniques by Southern Cross University researchers, has led to an ‘astounding’ new look at human evolution.

The University’s Geoarchaeology and Archaeometry Research Group (GARG) lead researcher Dr Renaud Joannes-Boyau was invited to collaborate in analysis of the fossil’s teeth because of his recognised international expertise in direct dating of human remains.

The confirmation of the ‘young’ age of the fossil Homo naledi – at between 236,000 and 340,000 years old – means that primitive hominids lived in Africa at almost the same time as humans, the first time this has been established.

The conclusion is outlined in an international multi-authored paper published in the journal eLife ‘The age of Homo naledi and associated sediments in the Rising Star Cave, South Africa’, led by Professor Paul Dirks and Associate Professor Eric Roberts of James Cook University (JCU).

The pair found Homo naledi deep in a cave system in South Africa in 2013.

Dr Joannes-Boyau’s contribution to this research project, was to conduct the first direct dating of Homo naledi’s tooth last year. The result was later blindly duplicated by another independent research group.

Dr Joannes-Boyau said the Homo naledi date was surprisingly recent.

“With an age between 236,000 and 340,000 years old, Homo naledi is an incredible fossil. You have to understand that, at first, most palaeoanthropologists believed the hominid was 1.5 to 2 million years old, because of its anatomical features.

“The accurate dating of Homo naledi was challenging but fascinating. When I first modelled the age, I had to go back and look at all my results again, as it was so unexpected,” he said.

The direct dating was performed at the University’s Lismore campus on a unique ESR spectrometer prototype, custom designed by Freiberg Instruments, using Uranium series dating (U-series) and electron spin resonance (ESR) dating.

Professor Paul Dirks from JCU worked with 19 other scientists from laboratories and institutions around the world, including seven Australian universities, to establish the age of the fossils.

“The dating of Naledi was extremely challenging. Eventually, by combining six independent dating methods we managed to constrain the age of this population of Homo naledi to between 236,000 and 335,000 years,” said Professor Dirks.

The age for this population of hominins shows that Homo naledi may have survived for as long as two million years alongside other species of hominins in Africa. More astounding, perhaps, is that at such a young age, in a period known as the late Middle Pleistocene, it was previously thought that only Homo sapiens (modern human) or their immediate ancestors existed in Africa. More critically, it is at precisely this time that we see the rise of what has been called “modern human behaviour” in southern Africa, behaviour attributed, until now, to the rise of modern humans and thought to represent the origins of complex modern human activities such as burial of the dead, self-adornment and complex tools.

“I remember back in 2013 when I was in South Africa with the team that discovered the remains,” Dr Joannes-Boyau said.

“With the first pictures they showed me of Homo naledi and with just a few handfuls of remains being excavated at the time, I already knew that like Au. Sediba, Naledi would change everything,” said Dr Joannes-Boyau.

“Although, there is still a lot to learn about Homo naledi and more dating to perform in the future, the age of the hominid completely reshapes our understanding of human evolution. It was not that long ago when we had this simple idea of a very linear human evolution. But for the past decade, discoveries have clearly shown the complexity of the human journey, and Homo naledi is definitely an incredible and central piece of the puzzle.

“With Homo Floresiensis, Homo (Sapiens) Denisova, Homo Neanderthalensis and now Homo naledi, we can see that it’s only recently that modern humans became the lone survivor after a complex and incredible journey that took place over millions of years of evolution. While at the present the oldest known remains for Homo Sapiens is slightly younger (200ka) than the Homo naledi deposition, future discoveries might show that the two very different species had overlapped in time, and potentially interacted in some forms.”

Background
Homo naledi had a tiny brain, about the size of an orange.
• It stood about 1.5 metres (about 5 feet) tall and weighed about 45 kilograms (almost 100 pounds).
Homo naledi‘s teeth and skull are similar to those of the earliest known members of our genus. The shoulders are more similar to those of apes and the extremely curved fingers suggest climbing ability. Its feet are similar to modern humans and this and its relatively long legs suggest it was well suited for long-distance walking.
• The discovery in 2013 of Homo naledi in the Rising Star cave system outside of Johannesburg, South Africa, was announced by the University of the Witwatersrand, the National Geographic Society and the South African National Research Foundation on September 10, 2015.

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