‘Taung Child’ fossil offers clues about the evolution of childhood

A fossil found in South Africa 100 years ago provides insights into the emergence of a crucial — and unusual — life stage

In November 1924 — on the day they were hosting a wedding at their Johannesburg home in South Africa — Australian anatomist and physician Raymond Dart and his wife Dora noticed two men staggering up the drive with two large boxes. According to Dart’s memoirs, written decades later¹, Dora had bemoaned the fact that the fossils Dart had been expecting had arrived on this day “of all days”. She had begged him not to “go delving in all that rubble until the wedding [was] over and everybody [had] left”.

The boxes contained what would become one of the world’s most famous fossils, the Taung Child.

In just a few weeks — astonishingly — Dart was able to use this one individual to surmise the broad course of human evolution as we understand it today. Previous evidence for human ancestry made use of fossils that bore a closer resemblance to modern humans. Dart’s description was astounding because it was of a species that was more apelike than humanlike, a revelation that in turn suggested that humanity’s evolutionary path had originated in Africa.

Dart’s report of the fossilized skull and matching endocast — an internal cast of the braincase formed from sediments that had accumulated in it — was published² in Nature on 7 February 1925. Both the discovery and Dart’s insights deserve to be celebrated. There were, however, things that Dart could not have known and details that he misconstrued. Today — a century on — the fossil is still prompting questions about human evolution.

Fresh finds

In his Nature paper, Dart argued that the Taung Child belonged to a previously unknown group of bipedal human ancestors that he called ‘man-apes’ or more formally, Australopithecus africanus, meaning southern ape from Africa.

Dart’s find was described in newspapers all over the world, and he became famous overnight. But it took decades and the discovery of more australopithecine fossils in South Africa before scientists began to accept his controversial ideas about human evolution. At the time, several fellows of the Royal Society of London thought that a specimen found in the village of Piltdown in East Sussex, UK, known as Piltdown Man (which was later exposed as a hoax), belonged to the oldest ancestor leading to modern humans.

But Dart’s ideas were eventually accepted. In fact, his announcement in 1925 nailed the big picture of hominin evolution as it is understood today. His claim that Taung belonged to a previously unrecognized group of early hominins that shared features of both humans and other living apes still holds. So does his inference that Taung was bipedal because of where the spinal cord entered the bottom of the skull. He also speculated correctly that the genus Homo arose from Australopithecus and that, as Charles Darwin had predicted³, the cradle of humanity was in Africa rather than in England or Asia.

Dart judged Taung to be a six-year-old child with a cranial capacity (a proxy for brain size) of 520 cubic centimetres⁴. He also estimated the fossil’s age to be about one million years. However, in the mid-1920s, few comparisons had been made of the development of humans and other apes after birth and during infancy and other life-history stages. Moreover, Dart did not have access to imaging technologies available today, which enable scientists to ‘see’ inside fossilized bones⁵, or to the techniques now used to date fossils.

Palaeoanthropologist Phillip Tobias (right) points out a feature on Taung’s endocast to Ramond Dart (left) and the author (D.F.) in 1984.Credit: Dean Falk

Since the mid-1980s, Taung’s age at death has been revised by researchers who study the evolution of growth and development in part by evaluating dental development and brain growth in an expanding record of fossil hominin juveniles⁶. We now know that Taung was around 3.8 years old when it died, with a brain of near-adult size and developmental maturity beyond that of a human of the same age⁶. (Some scientists think Taung was female because the best current estimate for its adult cranial capacity, around 405 cubic centimetres, is low for australopithecines, and female australopithecines had smaller braincases than males did⁷.) Another study indicates that Taung dates to about 2.58 million years ago, which is well within the range of 3.6 million to 2 million years ago for all of the Australopithecus specimens found in South Africa⁸.

These are not trivial revisions. On the contrary, they raise important questions about when, why and how an unusual life-history stage — namely childhood — evolved and what other changes (such as in brain size) accompanied its emergence.

Most ape infants can cling onto their mothers’ bodies actively by a few months after their birth, whereas human babies are slower to mature and remain dependent on their parents or carers for much longer. Indeed, most apes do not have a childhood — a period during which individuals who are weaned continue to be nurtured, mainly by their elders.

In her assessment of Taung’s baby teeth and first permanent molars, biological anthropologist B. Holly Smith concluded that Taung was maturing at the rate of a non-human ape and was well accustomed to solid foods, although it might still have received a low level of nursing. According to Smith, “Taung died at, or did not long survive, the transition to independent feeding, as a ‘weanling’.” It was not a “‘child’ in any scientific sense”⁶.

The revised estimates, suggesting an ape-like rate of development, indicate that — ironically — the Taung Child never had, and would never have had (even had it survived), a childhood⁶.

Childhood is probably a crucial innovation in human evolution because it creates the opportunity for offspring to learn much more from their nurturing elders than would otherwise be possible. In fact, the emergence of a prolonged period of dependency or ‘helplessness’ in human ancestors is widely thought to have produced conditions conducive to cognitive evolution.

At first blush, it might seem puzzling that australopithecines matured at an apelike pace even though they were bipedal. But unlike later hominins, australopithecines spent much of their time in trees and, like other apes, probably slept there. They would have needed the faster-developing apelike anatomy to climb and move through trees. The apelike development of Taung and other australopithecines suggests that delayed growth and childhood emerged only after the descendants of australopithecines had begun to live fully on the ground and had lost numerous arboreal adaptations. As terrestrial bipedalism became more habitual, evolutionary tweaks that slowed down and elaborated the development of nervous, skeletal and muscular systems probably repurposed much of the anatomy that had been needed for arboreal locomotion.

Into the unknown

Smith and others have suggested that, rather than emerging in australopithecines, childhood probably evolved in Homo erectus — possibly along with increased body size, brain size and cognitive capacities. Meanwhile, some researchers have found that the rate of dental growth in an approximately 1.77-million-year-old Homo fossil from Dmanisi, Georgia, was relatively high⁹ — similar to the rate of dental growth found in Taung and living great apes⁶. In this specimen, however, the formation of the posterior teeth was delayed, as it is in modern humans. Because Dmanisi individuals had brains that were not much bigger than those of great apes or australopithecines, some have suggested that this delay might have been associated with the emergence of childhood before a large brain evolved⁹.