Sterkfontein in brief
Sterkfontein (“strong spring” in Afrikaans) is a system of limestone caves about 40 kilometres northwest of Johannesburg, in South Africa’s Gauteng province. Over millions of years the caves have filled with rubble, sediment and the bones of animals that fell in, were dragged in by predators or lived there, and the cave deposits have since been exposed by mining and excavation. About 500 or more fossils of early humans and their relatives have come from there, the largest number from any one site.
The caves are part of the Cradle of Humankind, a group of fossil sites listed by UNESCO as a World Heritage Site in 1999.
Discovery
Limestone miners found the caves in the 1890s, and fossils turned up as lime was quarried. After the Australopithecus skull from Taung was described in 1925, Robert Broom, a Scottish doctor and paleontologist, looked for more. In 1936 he found part of an adult skull at Sterkfontein, and so the first adult of the species now called Australopithecus africanus was found. In 1947, with John Robinson, he found Sts 5, the skull nicknamed “Mrs Ples”, and a pelvis that showed upright walking.
From 1966 Phillip Tobias of the University of the Witwatersrand led excavations at Sterkfontein for many years. Ron Clarke, who had been Tobias’s student, took over the work in the 1990s and has led the excavation of Little Foot.
Little Foot
In the mid-1990s Ron Clarke noticed four foot bones in a box of fossils from the cave, apparently from an Australopithecus with a grasping big toe. He sent two workers to look for where they came from, and in 1997 they found the rest of the skeleton still in the rock of the cave, which then took about twenty years to remove and clean. The skeleton, StW 573 and nicknamed Little Foot, is the most complete early hominin skeleton of its age from the region. A 2015 study dated it to about 3.67 million years, though other methods give younger dates, and its date and species are debated. Clarke calls it Australopithecus prometheus, and others place it with africanus or in a separate species.
Other finds
- Sts 5, “Mrs Ples”. The best-known skull of A. africanus, found in 1947.
- Sts 14. A skeleton with a pelvis, vertebrae and ribs, found in 1947.
- StW 53. A skull found in 1976 that some researchers assign to early Homo, which would make Sterkfontein one of the oldest sites for the genus.
- Stone tools. Simple Oldowan tools in a younger layer, Member 5, dated to about 2 million years ago or a little later (estimates differ), and later Acheulean handaxes.
Neighbours in the Cradle
Within a few kilometres are other major sites: Swartkrans and Kromdraai (Paranthropus robustus), Drimolen (where a 2.04 million-year-old Homo erectus skull was found), Gladysvale, and Malapa, where Australopithecus sediba was found in 2008 by nine-year-old Matthew Berger and published in 2010. In 2013 cavers in the Rising Star Cave system found a narrow chamber filled with bones of a small-brained human species, Homo naledi, announced in 2015.
Why Sterkfontein matters
Together the Cradle caves show that South Africa had a variety of early human relatives between about 3.5 and 1 million years ago, living in the same landscape: australopiths, robust Paranthropus, and early Homo. They also hold the fossils of large numbers of animals, which help reconstruct the climate. Dating the deposits has proved difficult, and the ages of many fossils remain argued over.
Visiting
The Sterkfontein Caves are open for guided tours, which go underground to the excavation area and the chamber where Mrs Ples was found. The Maropeng visitor centre, a few kilometres away, has exhibitions on human evolution. Many sites in the Cradle, including those still being excavated, are not open to the public.
Sources
- Broom, R. and Robinson, J. T. (1947). Further remains of the Sterkfontein ape-man, Plesianthropus. Nature 160: 430 to 431.
- Granger, D. E. and others (2015). New cosmogenic burial ages for Sterkfontein Member 2 Australopithecus and Member 5 Oldowan. Nature 522: 85 to 88.
- Berger, L. R. and others (2010). Australopithecus sediba: a new species of Homo-like australopith from South Africa. Science 328: 195 to 198.
- Berger, L. R. and others (2015). Homo naledi, a new species of the genus Homo from the Dinaledi Chamber, South Africa. eLife 4: e09560.
- UNESCO World Heritage Centre. Fossil Hominid Sites of South Africa.