One hundred years ago, the discovery of a skull in the North West province of South Africa changed our understanding of human evolution. Raymond Dart, an anatomist at the University of Witwatersrand who first described the skull, named the young animal’s skull the Taung Child. In 1924, Dart could no longer determine the exact age of the skull, but announced that it belonged to a new species that he had discovered. Australopithecus africanusIt was the first evidence to confirm British naturalist Charles Darwin’s claim that apes and humans shared a common ancestor and that humanity originated in Africa.
After the Taung child, there are new discoveries of Australopithecus africanus were manufactured, many of them in Sterkfontein, about 70 km southwest of Pretoria. Sterkfontein is located in the “Cradle of Humankind”, a UNESCO World Heritage Site.
In the century since the Taung Child was found and described, a great debate has arisen about the geological age of the Australopithecus Fossils found at Sterkfontein, as well as those from Taung and a third site, Makapansgat.
Much of the controversy revolves around Sterkfontein. Some researchers estimate the age of fossils from a particular area (called “Member 4”) to be between 3.4 and 3.7 million years old. Others estimate that these fossils are much younger, dating back to 2 to 2.6 million years. The differences stem from the dating methods used by opposing teams. Each has published papers rejecting the other’s methods.
Now the controversy may be one step closer to a resolution. Together with my colleague Sue Dykes (who sadly passed away in 2019), I used a different approach, applied directly to the fossil teeth of hominins (humankind’s distant relatives), to estimate the Sterkfontein teeth. Australopithecus Age of the fossils. Our results for Member 4 suggest that the fossils are between 2 and 3.5 million years old, which is a longer time period than previously thought and includes the ages estimated by the opposing teams.
Using our method, we were able to date the life of the Taung child to 2.58 million years ago.
We believe our method is accurate, but there will undoubtedly be further studies using different methods. We are addressing a question that has puzzled scientists for decades, and the search for a definitive answer as to when these ancient members of our family tree existed in South Africa will continue.
One question that depends on the answer is the identification of the region from which our genus (homo) originated: Was it in South Africa or East Africa, from an ancestral species of Australopithecus?
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Different methods
One reason why it was difficult to determine the exact date of the Sterkfontein Australopithecus is that the first discoveries were made during the mining of limestone with dynamite. This means that the context of the fossils was lost.
However, fossils of animal species that are also found in East Africa have been found at Sterkfontein and elsewhere in South Africa. Volcanic deposits in East Africa contain trace amounts of potassium (K) and argon (Ar), which allow accurate K/Ar radiometric dating.
Unfortunately, there were no active volcanoes in South Africa during the period in question, 2 to 5 million years ago. However, fossils of species from both areas can be compared, including cattle (antelopes such as wildebeest, hartebeest and kudu), wild boar (such as warthogs) and monkeys, as well as geladas.
Because the East African fossils can be dated well using the precise K/Ar radiometry method, the age of the same species in South Africa can be estimated. This approach is called biochronology and is the reason why a group of researchers in the debate concluded that the Sterkfontein fossils from Member 4 are between 2 and 2.6 million years old. Essentially the same ages were determined by uranium-lead and paleomagnetic studies.
The group, which estimated the fossils to be between 3.4 and 3.7 million years old, used an approach called “cosmogenic nuclidates.” They reached their conclusions by using the elements beryllium and aluminum to estimate the age of chert (a type of sedimentary rock) in the Sterkfontein Cave deposits associated with hominin fossils from Member 4.
Our approach
We also used a biochronological approach to dating, but instead of using animal teeth, we dated directly from measurements of Australopithecus Teeth from fossils.
We investigated the length and width ratios of the lower first molars of East African hominins. We then used an equation we developed to quantify the relationship between these ratios and the geological age of our sample of Tanzanian, Kenyan and Ethiopian fossils, including Australopithecus afarensis and early homo Species such as H. habilisThe dates for this have been set.
Assuming that the age of South African fossils belonging to the same genera can be estimated from the same relationship, we applied the equation to lower first molars from Sterkfontein, in particular to those Australopithecus and early homofor the dental conditions. In this way, we were able to obtain dates for individual molars.
Our approach was applied to the molars of the Taung child and yielded a new result of 2.58 million years for this specimen of Australopithecus africanus.
Two teeth from Australopithecus from Makapansgat were also dated using our method. The specimens are 3.07 million and 3.00 million years old, respectively. This is in good agreement with previous estimates using paleomagnetism.
Using our method, we also attempted to date fossils that can be assigned to the hominin species known as Australopithecus sedibafound at Malapa near Sterkfontein. Our dates for two teeth of this type (catalogued as MH1 and MH2) are 2.14 million and 1.93 million years respectively. This corresponds very well to the age of 1.98 million years that we determined using methods using uranium, lead and paleomagnetism.
Our special thanks go to Jacopo Moggi-Cecchi for providing us with some of the measurements used in our study.
This edited article was republished by The conversation under a Creative Commons license. Read the original article.
