An international team of paleoanthropologists has unearthed a 2-million-year-old skull of Homo erectus, the first of our ancestors to be nearly human-like in their anatomy and aspects of their behavior, in the fossil-rich Drimolen cave system north of Johannesburg, South Africa.
This is an artist’s reconstruction of female Homo erectus from Dmanisi, Georgia. Image credit: Elisabeth Daynes, via tabula.ge.
Homo erectus is one of our direct human ancestors and is best known for migrating out of Africa into the rest of the world.
They walked upright and were a more human-like species than the other hominins found in the Cradle of Humankind.
Homo erectus had shorter arms and longer legs. They could walk and run for longer distances over the African grasslands than the others.
“The Homo erectus skull we found shows its brain was only slightly smaller than other examples of adult Homo erectus,” said Professor Andy Herries, a researcher at La Trobe University and the University of Johannesburg and corresponding author of a paper published in the journal Science.
“It samples a part of human evolutionary history when our ancestors were walking fully upright, making stone tools, starting to emigrate out of Africa, but before they had developed large brains.”
The 2-million-year-old fossil, designated DNH 134, was reconstructed from more than 150 individual fragments recovered from the Drimolen site over a five-year period.
“Before we found DNH 134, we knew that the oldest Homo erectus in the world was from Dmanisi in Georgia dating to 1.8 million years ago,” said co-author Stephanie Baker, a Ph.D. candidate at the University of Johannesburg.
“The newly-discovered fossil demonstrates that Homo erectus, our direct ancestor, clearly evolved in Africa,” added co-author Jesse Martin, a Ph.D. student at La Trobe University.
The DNH 134 Homo erectus cranium from South Africa. Image credit: Jesse Martin / Reanud Joannes-Boyau / Andy I. R. Herries.
The age of the DNH 134 skullcap shows something else — that at least three hominins lived in southern Africa at the same time.
“Unlike the world today, where we are the only human species, two million years ago our direct ancestor was not alone,” Professor Herries said.
“We can now say Homo erectus shared the landscape with two other types of humans in South Africa, Paranthropus robustus and Australopithecus.”
“This suggests that one of these other human species, Australopithecus sediba, may not have been the direct ancestor of Homo erectus, or us, as previously hypothesized.”
“The new crania offered an unparalleled insight into how three different human species, with quite different adaptations, shared a changing environment together,” said co-author Angeline Leece, a Ph.D. student at La Trobe University.
“The discovery raises some intriguing questions about how these three unique species lived and survived on the landscape,” said co-author Dr. Justin Adams, a researcher at Monash University.
“One of the questions that interests us is what role changing habitats, resources, and the unique biological adaptations of early Homo erectus may have played in the eventual extinction of Australopithecus sediba in South Africa.”
“Similar trends are also seen in other mammal species at this time. For example, there are more than one species of false saber-tooth cat, Dinofelis, at the site — one of which became extinct after two million years.”
“Our data reinforces the fact that South Africa represented a truly unique mixture of evolutionary lineages — a blended community of ancient and modern mammal species that was transitioning as climates and ecosystems changed.”
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Andy I.R. Herries et al. 2020. Contemporaneity of Australopithecus, Paranthropus, and early Homo erectus in South Africa. Science 368 (6486): eaaw7293; doi: 10.1126/science.aaw7293
