Embedded in the dolomitic rock within a dozen caves in the area now called the Cradle of Humankind are the fossilized remains of hominids that lived in South Africa up to 3.5 million years ago. Samples of fossilized pollen, plant material and animal bones also found in the caves indicate that the area was once a tropical rainforest inhabited by giant monkeys, long-legged hunting hyenas and sabre-toothed cats.
Quite when hominids arrived on the scene isn’t certain, but scientists now believe that the human lineage split from apes in Africa around five to six million years ago. The oldest identified group of hominids is Australopithecus, a bipedal, small-brained form of man. The first Australopithecus discovery in South Africa was in 1924, when Professor Raymond Dart discovered the Taung child in what is now North West Province. In 1936, australopithecine fossils were first found in the Sterkfontein Caves, and in 1947 Dr Robert Broom excavated a nearly complete skull which he first called Plesianthropus transvaalensis ("near-man" of the Transvaal), later confirmed as a 2.6-million-year-old Australopithecus africanus. Identified as a female, she was nicknamed "Mrs Ples", and for many years she was the closest thing the world had to what is dubbed "the missing link".
A number of even older fossils have since been discovered at Sterkfontein and nearby caves, along with evidence of several other genera and species, including Australopithecus robustus, dating from between one and two million years ago, and Homo ergaster, possibly the immediate predecessor of Homo sapiens, who used stone tools and fire.