Mrs. Ples: The Sterkfontein Skull, Her Age and Whether She Was Female

Sterkfontein is a cave site in Gauteng. On 18 April 1947, Robert Broom and John T. Robinson of the Transvaal Museum recovered an almost complete cranium from the breccia, the hard, cemented rubble that fills the old cave. It went into the catalogue as Sts 5. Broom and Robinson reported their Sterkfontein material in Nature that same year.

The extraction was not gentle. The skull broke into two pieces as it came out of the rock, reportedly after Broom used dynamite to expose it, according to the Smithsonian Human Origins Program. The break is part of the fossil's story.

Broom gave the skull a scientific name of its own: *Plesianthropus transvaalensis*, meaning "almost human of the Transvaal." He read it as an adult female. Shorten the genus name to "Ples," add "Mrs." for the female reading, and the nickname more or less writes itself. The genus name did not last, and the fossil is now placed in *Australopithecus africanus*, but the nickname stuck for good.

Broom was also one of the few scientists who had backed Raymond Dart's claims about an earlier South African fossil, a story told in full in our piece on the Taung Child.

Mrs. Ples mattered right away because she was a grown individual. The Taung Child, named by Dart in the 1920s, was a young child, and critics had argued that a juvenile could not show what the adults of its kind looked like.

An adult cranium answered that. Sts 5 showed that a mature *Australopithecus africanus* still had a small brain and a strongly projecting face. The Smithsonian notes that this supported the reading of the Taung Child as an early human relative rather than a young chimpanzee. A complete adult face, with the jaw pushed forward under a small braincase, gave everyone something solid to compare against.

The short answer is probably around 2.1 to 2.8 million years old, under the estimates most often used, with the age still argued. The Smithsonian's Sts 5 record gives 2.1 to 2.5 million years. Older accounts often placed her near 2.5 million years.

The uncertainty comes from the cave itself. Mrs. Ples came from a layer called Member 4, and different dating methods give Member 4 different ages. Wits University's 2024 explainer lays out the competing approaches. Here is how the main estimates compare.

An estimate of about 2.15 million years has also been cited for Sts 5 specifically. The Granger study is the outlier that pushed parts of Member 4 much older, and other researchers have not accepted that result. Taken together, the fair summary is a fossil a little over two million years old, perhaps closer to two and a half, with a real debate about how to read the cave. For a general look at how scientists put ages on old bones, see our story on how old bones are dated.

Nobody knows for sure, and scientists still disagree. The nickname reflects Broom's 1947 reading, not a settled fact. The question is sometimes put simply as "Señora o Señor Ples?", and scientists have been arguing both sides for more than forty years.

Broom judged Sts 5 to be an adult female because of its small canine sockets and its generally gracile, lightly built appearance. That view held for decades. Then the arguments began.

The most recent major argument came from Gaokgatlhe Tawane and Francis Thackeray in 2018. They measured the canine sockets and concluded that they are more consistent with a small male. The Ditsong Museums material and Thackeray's work lean toward male. Their reading has not ended the disagreement, though: Bonmatí and colleagues and Villmoare and colleagues had both made the case for a grown woman, and Sts 5 is still discussed as either a small male or an adult female.

A related puzzle involves a partial skeleton from the same site, Sts 14. A 2002 discussion asked whether Sts 14 could be the body that went with Mrs. Ples's head. Bonmatí and colleagues concluded in 2008 that Sts 5 and Sts 14 were not demonstrably the same individual. So, the skull still stands on its own.

Reading sex and age from a skull without the rest of the skeleton is hard even for much younger bones, as our story on what bones tell archaeologists explains. Whatever the answer turns out to be, Mrs. Ples was a real individual who lived and died at Sterkfontein, and the nickname is simply part of that individual's long life in science.

Three famous South African fossils get mentioned together, and it helps to know how they connect.

The Taung Child and Mrs. Ples belong to the same species, *Australopithecus africanus*. Raymond Dart described the Taung Child from Taung, South Africa, in the 1920s; it was a juvenile. Mrs. Ples, found at Sterkfontein in 1947, gave the species its classic adult face. Our Taung Child story covers that first find.

Little Foot is a different case. It is a much older and far more complete skeleton from the same Sterkfontein cave system, found by Ron Clarke and colleagues in the 1990s. It is generally treated as *Australopithecus prometheus*, although its classification has been debated, and a 2024 study gave it a biochronological age of about 3.6 million years. Same caves, then, but a different period and possibly a different species. For another well-known australopith from much farther north, read about Lucy.

The original Sts 5 fossil is curated by the Ditsong National Museum of Natural History in Pretoria, where it is associated with the museum's Broom Room. Public displays and visitor exhibitions may use casts rather than the original, so the skull you saw on a trip may well have been an exact replica.

The place where she was found is a separate visit. Sterkfontein Caves lie about 40 kilometres northwest of Johannesburg in Gauteng, inside the Cradle of Humankind UNESCO World Heritage Site. Maropeng is the official visitor centre for the wider Cradle of Humankind. Since 1 April 2024, Wits University has run research and visitor operations at the Sterkfontein and Swartkrans Caves, according to Wits Sterkfontein Caves, and Wits announced the reopening of the Sterkfontein Caves in April 2025.

Before you travel, confirm opening hours, tickets and whether the original or a cast is on show with Ditsong, Wits Sterkfontein Caves or Maropeng.

A few smaller questions come up again and again.