Athena Review Image Archive ™
Mrs. Ples skull and brain endocast
Skull and brain endocast of A. africanus, Mrs. Ples (photo: Transvaal Mus.)
In 1947 Robert Broom and John T. Robinson found a nearly complete skull of an adult hominin in a cave near Sterkfontein, South Africa. The site is about 40 km NW of Johannesburg in a limestone region of the Transvaal. Based on tooth analysis, the fossil is considered that of an adult female.The skull was nicknamed "Mrs. Ples" from the name Plesianthropus transvaalensis ("near-man from the Transvaal"), that Broom initially gave the skull. It is now considered part of the species Australopithecus africanus, and this is the most complete A. africanus skull known.
Mrs. Ples had a brain size or cranial capacity of about 485 cubic centimetres, only slightly larger than that of a chimpanzee. Her skull also revealed that she walked upright, based on the location of the foramen magnum on the underside of the skull, where the medulla oblongata also lies, as opposed to near the back of the skull as in the case of anthropoid apes. This was one of the first fossils (along with the Taung child skull found by Dart in 1924) to reveal that upright walking had evolved well before any significant growth in brain size. The fossil has been dated by a combination of palaeomagnetism and uranium-lead techniques to ca. 2.05 million years ago.
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