Many Australopithecus fossils have been found near Sterkfontein, about 40 kilometres (25 mi) northwest of Johannesburg, in a region of Gauteng (part of the old Transvaal) now designated as the Cradle of Humankind World Heritage Site.

It derives from the scientific name Plesianthropus transvaalensis (near-man from the Transvaal), that Broom initially gave the skull, later subsumed (synonymized) into the species Australopithecus africanus.

This was a surprise to anthropologists at the time, because it had been assumed that the big brain of Homo had preceded, or at least evolved in tandem with, our upright gait.

Some experts have suggested that a partial skeleton, known only by its catalogue number of STS 14, which was discovered in the same year, in the same geological deposit and in proximity to Mrs. Ples, may belong to this skull.

This skull, along with others discovered at Taung, Sterkfontein, and Makapansgat offered compelling evidence in favour of Charles Darwin's hypothesis that humanity's origin lay in Africa.

[6] But a more recent study, using the size of the teeth of Theropithecus oswaldi, concluded that there is no evidence that any of the South African cave sites are older than about 2.8 million years.