“OUR POOR COUSINS”
THE LATER AUSTRALOPITHECINES AND THEIR EXTINCTION
2.6-1.0 million years ago
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| Reconstruction of the skull of the later robust australopithecine, Australopithecus boisei, about 1.8 million years old. This was an East African form of the robust australopithecines and co-existed in that region with early forms of our genus, Homo. Credit: Photo by Kathy Schick, courtesy of the Stone Age Institute. |
There was more than one evolutionary experiment in upright walking. One branch, represented by the genus Homo, led to us. Another branch, represented by the so-called “robust australopithecines”, co-existed with our ancestors for over one-and-a-half million years. These bipedal hominins were characterized by small front teeth and huge cheek teeth, a slightly larger brain than earlier australopithecines (~550 cc), flared cheek bones, and, in males, a bony (sagittal) crest running down the center of the skull for the attachment of massive chewing muscles.
First put into the genus Australopithecus, many anthropologists now believe their morphology is unique enough to warrant their own genus, Parathropus. In East Africa, the earlier form is called Paranthropus aethiopicus and the later form Paranthropus boisei, and in South Africa the form is called Paranthropus robustus. Tooth-wear suggests these forms were eating hard food items such as seeds. With smaller brains, they were likely less of a tool-maker than the larger-brained Homo forms. They go extinct in East and South Africa by one million years ago, while the genus Homo (and stone tools) continue and thrive over time. It is likely that these forms were too specialized in their adaptation, and when the environment changed they were less able to adapt to new conditions.
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| Comparison of the lower jaw of Australopithecus boisei (top) with that of a modern human. Credit: Photo by Kathy Schick, courtesy of the Stone Age Institute. |
HOW DO WE KNOW?
Hundreds of fossils of robust australopithecines have been found at well-dated sites in Ethiopia, Kenya, Tanzania, Malawi, and South Africa.
WHY SHOULD I CARE?
Although the robust australopithecines were not our direct ancestors, they co-evolved with early genus Homo and could have produced some of the stone tools that we find in the archaeological record. Their total extinction by 1 million years ago shows that there were several experiments in upright walking, and these were the experiments that ultimately failed.
WEB RESOURCES
This is a BBC website about Lucy and other facts of hominin evolution.
https://www.bbc.co.uk/sn/prehistoric_life/human/human_evolution/mother_of_man1.shtml
This site has a lot of information about australopithecines, young and old.
https://www.talkorigins.org/faqs/homs/species.html#afarensis
This is a comprehensive Wikipedia web site about the Australopithecines.
https://en.wikipedia.org/wiki/Australopithecus
Stanford University’s website briefly outlines and highlights basic information about the Australopithecines.
https://www.stanford.edu/~harryg/protected/chp18.htm
This website provides a detailed description of Australopithecine evolution, with a respectable list of references.
https://tolweb.org/treehouses/?treehouse_id=4438
This webpage provides a narrative version of Australopithecine evolution. There is also a link on this page to an article about human hand evolution.
https://evolution-of-man.info/combined.htm
