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| Catalogno. | STS 5 |
|---|---|
| Common name | Mrs. Ples |
| Species | Australopithecus africanus |
| Age | c. 2.35 million years |
| Place discovered | Sterkfontein,South Africa |
| Date discovered | 18 April 1947 |
| Discovered by | Robert Broom andJohn T. Robinson |
Mrs. Ples is the popular nickname for the most complete skull of anAustralopithecus africanus ever found inSouth Africa. ManyAustralopithecus fossils have been found nearSterkfontein, about 40 kilometres (25 mi) northwest ofJohannesburg, in a region ofGauteng (part of theold Transvaal) now designated as theCradle of HumankindWorld Heritage Site. Mrs. Ples was discovered byRobert Broom andJohn T. Robinson on April 18, 1947. Because of Broom's use of dynamite and pickaxe while excavating, Mrs. Ples's skull was blown into pieces and some fragments are missing. Nonetheless, Mrs./Mr. Ples is one of the most "perfect" pre-human skulls ever found. The skull is currently held at theDitsong National Museum of Natural History inPretoria.
The nickname "Mrs. Ples" was coined by Broom's young co-workers. It derives from the scientific namePlesianthropus transvaalensis (near-man from the Transvaal), that Broom initially gave the skull, later subsumed (synonymized) into the speciesAustralopithecus africanus. In scientific publications, the specimen is referred to by its catalogue number, STS 5.[1]
The genusAustralopithecus, of which there are several species, is considered the likely precursor of the genusHomo. Though itscranium is comparable to achimpanzee's,Australopithecus walked upright, as humans do. This was a surprise to anthropologists at the time, because it had been assumed that the big brain ofHomo had preceded, or at least evolved in tandem with, our upright gait. Mrs. Ples, whose cranial capacity is only about 485 cubic centimetres (29.6 cubic inches),[2] was one of the first fossils to reveal that upright walking had evolved well before any significant growth in brain size.
The sex of the specimen is not completely certain and soMrs. Ples may in fact beMr. Ples. Moreover, X-ray analysis of the specimen's teeth (see below) has suggested it was an adolescent. Hence a designation ofMiss Ples orMaster Ples is also possible.
The paleoanthropologist Prof.Frederick E. Grine has studied the dental morphology of Mrs./Mr. Ples with a view to finally establishing Mrs./Ms. Ples's sex.[3] Using theComputed Tomography (CT) scans of STS 5 from the experiments of Weber et al., (2012) they compared them to CT scans of more recently discoveredA. africanus skulls from Sterkfontein. These scans allowed Grine to reconstruct the roots of the teeth, in order to see how the molar and canine teeth developed. This study concluded that Mrs./Mr. Ples was indeed a middle-aged female. However, the question is not entirely settled, since other studies have come to the opposite conclusion.
Some experts have suggested that a partial skeleton, known only by its catalogue number ofSTS 14, which was discovered in the same year, in the same geological deposit and in proximity to Mrs. Ples, may belong to this skull. If correct, this would make Mrs. Ples the South African counterpart to the famousLucy fossil. This skull, along with others discovered atTaung, Sterkfontein, andMakapansgat offered compelling evidence in favour of Charles Darwin's hypothesis that humanity's origin lay in Africa.[4]
The fossil was originally dated by a combination ofpalaeomagnetism and uranium-lead techniques to 2.1-2.6 million years ago.[5] A 2022 study dating surrounding rocks with a new methodology, stated their age as 3.4-3.7 million years old.[6] But a more recent study, using the size of the teeth ofTheropithecus oswaldi, concluded that there is no evidence that any of the South African cave sites are older than about 2.8 million years.[7]
In 2004, Mrs. Ples was voted 95th in theSABC 3's ande.tv'sGreat South Africans Top 100 list.
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