JARED DE CANHA
The origin of our species has sparked scholarly debates over the centuries and has produced some of the most significant scientific works of our time. This is why the discovery of Homo naledi, announced by the University of Witwatersrand in September, has turned the world’s focus to our backyard.
The remains of this prehistoric hominid species were discovered by Steven Tucker and Rick Hunter, recreational cavers that stumbled upon the fossils just outside Krugersdorp almost two years ago. The discovery was made in the Dinaledi chamber of the Rising Star cave system and led to the fossil species being named after the Sotho word for star: naledi. Determining the genus name for these fossils proved to be challenging, as researchers first had to determine whether the naledi fossils belonged in the Homo or Australopithecus genus. After carefully examining the skulls of the fossils, it was determined that they belonged in the Homo genus due to the shape and distinct brow ridges of the skulls.
The announcement was made by the Evolutionary Studies Institute (ESI) at Wits University in a press release titled “New species of human relative discovered in South African Cave” on 10 September 2015. This coincided with the publication of two papers in the scientific journal eLife and the cover story in National Geographic magazine’s October issue. Prof. Lee Berger, a research professor and palaeontologist at the ESI at Wits, explained the fascination with the discovery: “This is the most significant and extensive discovery of early human relatives’ fossils ever made on the continent of Africa.” Prof. Berger went on to say that this discovery was truly “remarkable” because it uncovered approximately 1550 fossils of 15 individuals, including infants, children, adults and the elderly.
Homo naledi’s physical features are of significance because, according to Prof. Burger, they are a “combination never seen before in the fossil record”. Homo naledi skulls are believed to have once housed brains approximately 6.3 cm in diameter, which is half the size of a modern human’s brain. Homo naledi fossils also indicate that the average specimen weighed approximately 45 kg and was no taller than 1.5lm. The average modern human weighs roughly 60 kg and is approximately 1.7 m tall. The position and structure of Homo naledi’s shoulders also gives an insight into the lifestyle of this species, as these show that Homo naledi climbed and hung from trees. This is further supported by Homo naledi’s strongly curved fingers. The palms, wrists and thumbs of the fossils found indicate that Homo naledi, nevertheless, had human-like characteristics and may have utilised primitive tools. Homo naledi also possessed similar feet and legs to modern humans that indicate that they were bipedal and could walk upright over long distances.
The most significant similarity between modern humans and Homo naledi can be seen in the way that both species treat their deceased. The remote location of the discovery of the fossils in the Dinaledi chamber suggests that Homo naledi disposed of their dead in a ritualised manner. Prof. Paul Dirks, a professor at James Cook University in Queensland, Australia, said that the Dinaledi cave had “always been isolated from the other chambers and [had] never been open directly to the surface”. Prof. Dirks indicated that the fact that the remains were found almost alone in the remote chamber is of importance. The Wits research team explained that the fossils do not bear any scavenger or carnivore markings and are missing signs that other agents or natural processes, such as moving water, carried the fossils into the Dinaledi chamber. “We have explored every alternative scenario, including mass death, an unknown carnivore, water transport from another location or accidental death in a death trap,” explained Prof. Berger. This has led to researchers proposing that the only plausible explanation is that Homo naledi, like modern humans, intentionally disposed of their dead, which suggests a form of ritualised or repeated behaviour originally believed to be unique to humans.
This discovery has raised the question of where Homo naledi will slot in when considering the well-documented fossil history of early human remains. Researchers have struggled to date these fossils, particularly because of the absence of other animal fossils to date them against, making it impossible to determine the exact position that Homo naledi fills in the earth’s paleontological timeline.
Homo naledi is one of the many valuable fossils found in South Africa that have shed light on the past. Other significant South African fossil discoveries include two examples of Australopithecus africanus, the Taung Child in 1924 and Mrs Ples in 1947, as well as specimens of Australopithecus robustus and Australopithecus sediba in 1994 and 2008 respectively.
The Homo naledi exhibition at Maropeng museum. Photo: Shen Scott