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Two years ago, scientists unveiled to the world Homo naledi: a new species of hominin and a potential ancestor of Homo sapiens (modern humans).
Discovered deep in the Dinaledi chamber – part of the Rising Star cave system nestled in the Cradle of Humankind – were 1550 fossil elements and 15 Homo naledi skeletons.
While the discovery of Homo naledi was one of the best documented in the history of hominins, the species soon proved to be an enigma to researchers.
Homo naledi’s small skull and brain size suggested a close relationship to earlier, more primitive hominins.
Yet, at the same time, the species displayed modern, human-like features.
Now, the team of scientists and researchers who uncovered Homo naledi have announced two major new findings: the age of the original remains and a second chamber full of skeletons.
According to Wits paleoanthropologist Professor Lee Berger, who led the team, Homo naledi lived between 236 000 and 335 000 years ago.
“This places this population of primitive small-brained hominins at a time and place that is likely alongside Homo sapiens,” Berger said.
The shockingly young age of Homo naledi provides the first evidence that another species of hominin may have existed alongside the first humans in Africa.
“We can no longer assume that we know which species made which tools, or even assume it was modern humans that were the innovators of some of these critical technological and behavioural breakthroughs in the archaeological record of Africa,” Berger said.
Paul Dirks, a geologist at James Cook University and Wits, worked with 19 other scientists around the world and used six different independent dating methods to establish the age of Homo naledi to the late Middle Pleistocene Age – a period of time when it was previously thought only Homo sapiens existed in Africa.
According to Berger and Dirks, this means that Homo naledi may have survived for as long as two million years alongside other species of hominins in Africa.
“This is a humbling discovery for science,” Berger said.
“We can never assume that what we have tells the whole story.”
Berger and his team discovered more of that story when they uncovered more than 130 hominin species and the remains of at least three individuals in the Lesedi chamber, a cave 100m from the Dinaledi chamber where the original fossils were first found.
While the newly discovered fossils have not been dated, University of Wisconsin-Madison Professor John Hawks, the lead author on the paper describing the discovery, is confident that the skeletal remains not only are similar in age to that of the Dinaledi fossils but also belong to members of the same species.
Excavators uncovered the skeletal remains of a juvenile and two adults, one of which is an adult male called “Neo”, which means “gift” in Sesotho.
“The skeleton of Neo is one of the most complete ever discovered, and technically even more complete than the famous Lucy fossil, given the preservation of the skull and mandible,” Berger said.
Professor Peter Schmid of the University of Zurich, who led the reconstruction of the fossils, said the well-preserved nature of the fossils, especially the skull, provides researchers with a better idea of what Homo naledi actually looked like.
“We finally get a look at the face of Homo naledi,” Schmid said.
And according to Hawks, Neo “is one of the most significant discoveries ever made in the Cradle of Humankind and the continent of Africa” and constitutes one of the “best understood samples of hominins outside of Neanderthals and humans”.
Even though there is not enough research or evidence to definitively conclude how Homo sapiens are related to Homo naledi or why Homo sapiens survived and Homo naledi did not, the team believes that the full story of human evolution is not yet complete.
“Recently, the fossil hominin record has been full of surprises, and the age of Homo naledi is not going to be the last surprise that comes out of these caves I suspect,” Berger said.
Berger and his team published their newest findings in three papers in the open-access journal eLife detailing the age of the original fossils, the discovery of a second chamber in Rising Star and, more controversially, the evolution and behaviour of Homo naledi.
The fossils from the new discovery as well as the Homo naledi fossils from the first Rising Star expedition will be put on public display at the Maropeng Visitor Centre for the Cradle of Humankind from May 25.
The exhibit will be the largest display of original fossil hominin material in history.
