Famous Taung Child fossil from South Africa is 2.58 million years old, new study finds

The Taung Child fossil, a significant discovery in the field of human evolution, has been studied to determine its age. Around a century ago, Raymond Dart, an anatomist at the University of the Witwatersrand, named and described the skull found in South Africa's North West province as the Taung Child. Dart identified it as belonging to a new species called Australopithecus africanus, providing evidence that supported Charles Darwin's theory of a shared ancestor between apes and humans. The subsequent findings of Australopithecus africanus fossils in Sterkfontein, located within the "Cradle of Humankind," led to debates regarding their geological ages, including those at Taung and Makapansgat.

Conflicting dating methods have contributed to the controversy surrounding the ages of the Sterkfontein Australopithecus fossils, specifically those from a particular area known as "Member 4." Some researchers estimate the fossils in Member 4 to be between 3.4 and 3.7 million years old, while others believe them to be younger, dating back to 2 million and 2.6 million years ago. However, a novel approach using fossil teeth as a basis for estimating ages has shed new light on this matter.

In collaboration with my colleague Sue Dykes, we employed a distinct method directly applied to the fossil teeth of hominins to estimate the ages of Sterkfontein Austalopithecus fossils and the Taung Child. Our findings suggest that the fossils in Member 4 range in age between approximately 2 million and 3.5 million years, encompassing a wider timeframe than previously thought and incorporating both opposing age estimates.

We believe that our method provides accurate results, although future studies employing alternative approaches may yield further insights. Determining the precise existence of these ancient members of our evolutionary tree in South Africa remains an ongoing endeavor that has fascinated scientists for decades. Additionally, solving this question has implications for recognizing where our genus, Homo, originated—whether in South Africa or East Africa, from a common ancestor species of australopithecines.

Dating the Sterkfontein Australopithecus fossils accurately has proven challenging due to the loss of contextual information caused by their initial discovery during limestone mining events involving dynamite. Nonetheless, by comparing fossils of species found in both South Africa and East Africa, along with the presence of volcanic deposits containing potassium (K) and argon (Ar) in East Africa, researchers have been able to use the reliable K/Ar radiometric dating method. While active volcanoes did not exist in South Africa between 2 million and 5 million years ago, similar species found in both regions offer insights into dating the fossils.

Our approach also utilizes biochronology, but instead of analyzing animal teeth, we directly analyze the teeth of Australopithecus fossils. Specifically, we examined the length and breadth ratios of lower first molars of East African hominins to develop an equation quantifying the relationship between these ratios and geological age using a sample of well-dated fossils from Tanzania, Kenya, and Ethiopia. We then applied the equation to the lower first molar teeth attributed to Australopithecus and early Homo species, including tooth ratios determined in Sterkfontein. This enabled us to obtain dates for individual molars, including the Taung Child, which we dated to be approximately 2.58 million years old.

Furthermore, we used our method to date two Australopithecus teeth from Makapansgat, which yielded ages of 3.07 million and 3.00 million years, aligning well with previous estimates based on palaeomagnetism. Additionally, we applied our approach to fossils attributed to Australopithecus sediba, discovered at Malapa near Sterkfontein. The teeth representing this species, cataloged as MH1 and MH2, yielded dates of 2.14 million and 1.93 million years, respectively, remarkably consistent with the age of 1.98 million years obtained through uranium-lead dating and palaeomagnetism.

In conclusion, our biochronological approach utilizing dental measurements has provided valuable insights into the ages of key fossils, including the Taung Child. By refining our understanding of these ancient inhabitants of South Africa, we contribute to the ongoing pursuit of unraveling human evolution's mysteries and the quest to pinpoint the origin of our Homo genus—a geographic puzzle that awaits further investigation.

Earlier, SSP wrote about fossil discoveries augment Europe's significance in Great Ape evolution.