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New research published in South African Journal of Science offers a continuation of the debate that ‘Mrs Ples,’ the 2.5 million year old Australopithecus africanus skull found in the Sterkfontein Caves in 1947, by paleontologist Dr. Robert Broom and his assistant, John Robinson, is actually a male. Soon after the two made their landmark discovery, Broom confidently claimed that Mrs Ples was female based on the size of specimen’s canine sockets.

As we know, all primate adult males have larger canines than females. This clam was a visual deduction. The fossil record at that time he did not have a substantial comparative sample for the species, so there was room for doubt.

A study of “Mrs” Ples’ tooth sockets has made scientists think differently about “her” sex. Credit: Ditsong National Museum of Natural History

A study of “Mrs” Ples’ tooth sockets has made scientists think differently about “her” sex. Credit: Ditsong National Museum of Natural History

Since Mrs Ples’ teeth weren’t preserved, the authors of the new study carefully compared her tooth sockets. Mrs Ples’ sockets are in fact the size one would expect for a female, but this observation isn’t completely authentic…  Initially, Broom used a hammer and chisel to remove the hard calcified sands that surrounded Mrs Ples in the caves.  Later, Robinson used acetic acid to remove further rock – and some fossils, Mrs Ples among them, were damaged in the process. Because of acid used during work done on the skull about 60 years ago, parts of the skull and sockets were digested away.

The argument that Mrs Ples is a male or a female has been hotly debated for decades. In 1983 on the first challenges of Broom’s observation came from Yoel Rak, who argued that the prominent ridges on Mrs Ples’ snout indicated large roots of the canine teeth. This was supported by subsequent research. In 2012, Grine published an article which re-examined the available evidence and the pendulum swung back to the other side. He insisted Mrs Ples was “an adult female,” and that assertion was based in part on the apparently small size of the canine tooth sockets.

While it isn’t much significance, aside from understanding anatomical sexual dimorphism of A. africanus, this debate findings outlines science is a work in progress. Scientists don’t always agree, and they don’t always have the definitive answers. Sometimes it can take decades, or even centuries, to reach a resolution.

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