An Australopithecus partial cranium found in the Jacovec Cavern of the Sterkfontein Caves, South Africa, one of the richest early hominin fossil localities in Africa, shows striking similarities to that of our own, according to new research.
Forensic facial reconstruction of Australopithecus. Image credit: Cicero Moraes / CC BY-SA 3.0.
The hominin cranium, probably of Australopithecus anamensis, was discovered in 1995 in the roof of the eastern part of the Jacovec Cavern, and was described as the ‘oldest evidence of human evolution in South Africa.’
Now, Dr. Amelie Beaudet from the University of the Witwatersrand and co-authors have scanned the specimen and applied advanced imaging techniques in ‘virtual paleontology’ to further explore its anatomy.
“The Jacovec cranium represents a unique opportunity to learn more about the biology and diversity of our ancestors and their relatives and, ultimately, about their evolution,” Dr. Beaudet said.
“Unfortunately, the cranium is highly fragmentary and not much could be said about the identity nor the anatomy of the specimen before.”
Through high resolution scanning, the researchers were able to quantitatively and non-invasively explore fine details of the inner anatomy of the Jacovec specimen and to report previously unknown information about the genus Australopithecus.
“Our study revealed that the cranium of the Jacovec specimen and of the Ausralopithecus specimens from Sterkfontein in general was thick and essentially composed of spongy bone,” Dr. Beaudet said.
“This large portion of spongy bone, also found in our own cranium, may indicate that blood flow in the brain of Australopithecus may have been comparable to us, and/or that the braincase had an important role in the protection of the evolving brain.”
Skull vault thickness cartographies of the Jacovec cranium (StW 578) compared to three Australopithecus (StW 505, Sts 5 and Sts 71 from Sterkfontein), one Paranthropus (SK 46 from Swartkrans), one extant human (EH) and one extant chimpanzee (EC) crania. Topographic thickness variation is rendered by a pseudocolor scale (in mm) ranging from thinner dark blue to thicker red. All color maps are shown at the same relative scale, except the chimpanzee individual in lateral right (left column), lateral left (middle column) and superior (right column) views. In all individuals, the color map corresponds to the portion of the cranial vault above the transverse plane passing through the glabella and the opisthocranion. Scale bars – 2 cm. Image credit: Beaudet et al, doi: 10.1016/j.jhevol.2018.04.004.
In comparing this cranium to that of another extinct group of our family tree, Paranthropus, that lived in South Africa along with the first humans less than 2 million years ago, the team revealed an intriguing and unexpected aspect of the cranial anatomy in this genus.
“We also found that the Paranthropus cranium was relatively thin and essentially composed of compact bone,” Dr. Beaudet said.
“This result is of particular interest, as it may suggest a different biology.”
“The Jacovec cranium exemplifies the relevance of the Sterkfontein fossil specimens for our understanding of human evolution,” she added.
“Imaging techniques open unique perspectives for revisiting the South African fossil assemblage.”
The findings appear in the Journal of Human Evolution.
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Amélie Beaudet et al. Cranial vault thickness variation and inner structural organization in the StW 578 hominin cranium from Jacovec Cavern, South Africa. Journal of Human Evolution, published online May 23, 2018; doi: 10.1016/j.jhevol.2018.04.004
