In February 1925, Nature published a paper by Raymond Dart, an anthropologist who spent much of his working life describing the first hominin fossil ever found, Australopithecus Africanus – now known as the Taung Child.
The fossil, named after the small town near where it was found, led to the understanding that humans and their ancestors evolved in Africa. After years of scientific denial, it is now a widely accepted fact.
Charles Darwin had a hunch that our origins lay in Africa, but at the time of the Taung Child’s discovery, most scientists were convinced that humanity originated in Asia and Europe. Homo erectus, the oldest known hominin with a human-like body, had been found in Java in Asia in 1891. Fossils of Homo neanderthalenis, our closest human relative, had been found in Europe by 1829 due to Neanderthals. Complicating the timeline was Piltdown Man, believed to be the ‘missing link’ between apes and humans until he was exposed as a forgery in 1949, 37 years after his ‘discovery’.
“There was an element of disbelief, mixed with a huge dose of racism, because they couldn’t imagine that humans emerged from Africa. That made many scientists dismiss it,” says Rebecca Rogers Ackermann, co-director of the Human Evolution Research Institute at the University of Cape Town, South Africa.
In 1936, Robert Broom, as Dart, of the University of the Witwatersrand (Wits), in Johannesburg, found the first adult Australopithecus in the Sterkfontein Caves in South Africa. And in 1947, Broom and John Robinson discovered Ms. Ples 3,4 – the most complete skull of an Au africanus yet found.
John Hawks, a paleoanthropologist at the University of Wisconsin-Madison, says that Australopithecus, and the Taung skull in particular, combined three things in a way that no scientist had predicted.
First, it had a small brain—equivalent to or smaller than a gorilla of the same dental age, slightly larger than the brain size of a chimpanzee.
Second, the teeth were human-like, but with a twist: Taung has fairly large molars, with a generally human-like shape, and the deciduous incisors are small with no space between them. These differ from the jaws and teeth of young gorillas and chimpanzees.
Third, the species walked upright. The preserved face allowed Dart to estimate the size and shape of the base of the skull, in particular, the position where the spine would support the skull, which indicated that the head was held in an upright position.
Darwin believed that these characteristics must have evolved more or less together, as a system. That is, the gradual change in brain size, in diet (reflected by teeth), and in posture must have all kept pace with each other. Or, if one of those anatomical regions was changing faster, it must have been the brain.
“But Australopithecus was the first real new evidence. And it showed clearly that this idea, Darwin’s idea of human origins, was backward,” says Hawks.
“Bipedalism came first, changes in tooth shape and reductions occurred before the evolution of smaller molars, and the large brain was last. Darwin was wrong.”
A hundred years later, in the human fossil record, the genus Australopithecus is represented by a diverse group of five fossil species found throughout Africa. It fills the transitional space between the smaller-bodied hominins, the apes, and the hominins that ultimately contributed to our evolution.
