La Trobe University:
A partial skull found in South Africa suggests Homo erectus—an ancestral human species—appeared 100,000 years earlier than previously thought. The new research also shows that H. erectus lived alongside two other hominin species, neither of which were human.
A skull cap belonging to a Homo erectus toddler has been dated to between 2.04 million and 1.95 million years old, according to new research published today in Science. The cranial remains of another extinct hominin, Paranthropus robustus, were unearthed from the same deposits and assigned the same date range.
Both fossils were found at the Drimolen site, one of several important South African paleoanthropological sites collectively known as the Cradle of Humankind. The new paper, led by Andy Herries from the University of Johannesburg, was an international collaboration involving researchers from La Trobe University in Australia and Washington University in St. Louis.
There’s a lot to unpack with these new findings, but the many anthropological implications are important.
First and foremost, the H. erectus skull cap, named DNH 134, is now the oldest evidence we have of this species—arguably the most successful human group to have ever lived. These now-extinct humans lasted for more than 1.5 million years, spreading into Asia and Indonesia. They may also be directly related to Homo sapiens, though many different hominins contributed to the crazy-quilt that is our species.
The authors of the new study “provide the most precisely dated remains in South Africa, add more than 100,000 years to the first appearance dates of… H. erectus, and reveal that H. erectus was a group of wanderers from the start,” wrote New York University anthropologist Susan Anton, who wasn’t involved with the new study, in a related Insights article.
The presence of H. erectus in South Africa during this time period also damages a theory that proposes Asia as the birthplace of this species. Prior to this discovery, the oldest H. erectus fossils were found at the Dmanisi site in Georgia, dated at 1.8 million years old, and the Koobi fora site in Kenya, dated to 1.7 million years old. That H. erectus originated in Africa, and not Asia, is supported by other recent evidence as well.
We already knew that H. erectus had a penchant for migration, but this discovery is further affirmation of their restless ways. Assuming they originated in Africa some 2 million years ago, as this new research suggests, they eventually spread north, arriving in what is now Georgia (a country located immediately northeast of Turkey) some 200,000 years later. And by around 1.3 million to 1.5 million years ago, there made it to the Indonesian island of Java. Wow.
DNH 134 is the first H. erectus skull to be found in South Africa, dating back to the region’s Early Stone Age.
“Until this find, we always assumed Homo erectus originated from eastern Africa,” said Stephanie Baker, a researcher and PhD candidate at the University of Johannesburg, in a press release. “But DNH 134 shows that Homo erectus, one of our direct ancestors, possibly comes from southern Africa instead. That would mean that they later moved northwards into East Africa. From there they went through North Africa to populate the rest of the world.”
And yet there’s even more to this discovery, as the same cave deposits yielded another fascinating skull fragment, one belonging to a species known as Paranthropus robustus. This is interesting because another non-human hominin, Australopithecus, also dates back to this same time and place. Fossilized remains of Australopithecus sediba were previously uncovered at a nearby site called Malapa and dated to around 1.98 million years old.
If the new research is correct, this means three different hominin genera—Homo, Paranthropus, and Australopithecus—were stomping around South Africa’s Karst landscape some 2 million years ago. The new paper is the first to show that these three hominins lived at roughly the same place and at the same time.
As to how these three genera interacted with each other is anyone’s guess, but their contemporaneous presence may have had something to do with major climate shifts happening around this time. More on this in just a bit.
The presence of H. erectus at this early stage in human evolution rocks the anthropological boat for yet another reason. It has been proposed that Australopithecus sediba is the immediate ancestral species to H. erectus.
“DNH 134 being older than A. sediba complicates the likelihood of this species being ancestral to Homo in South Africa, as previously suggested,” wrote the authors in their paper.
Hey, no one said the study of human origins was going to be easy.
To reach the proposed date range for these fossils, the researchers combined multiple techniques: uranium-lead dating was used on flowstones, uranium-series electron spin resonance was used to date the teeth, and palaeomagnetism was applied to cave sediments. Together, these methods yielded the dates between 2.04 million and 1.95 million years old.
The P. robustus cranium, called DNH 152, was relatively easy to identify, but the same can’t be said for the DNH 134 cranium, which consists of a small skull cap belonging to a toddler who died between the age of 2 and 3 years old. The “specimen preserves characters that align it morphologically” with H. erectus, including a teardrop shape and relatively large brain case, according to the paper.
If there’s a weakness to the new paper, this is it. Identifying a hominin species from an immature, partial cranium is a precarious proposition at best. Given the presence of other humans living at the same time, namely Homo habilis and Homo rudolfensis, it’s not unreasonable to think that the DNH fossil could represent something other than H. erectus. Humans, after all, have been around for some 2.8 million years. Writing in her accompanying Insights article, Anton allayed some of my concerns, but only partially:
How firm are the species identifications? DNH 152 was recognized as P. robustus on the basis of dental morphology, but the DNH 134 [designation] is less firm. The size and shape of the DNH 134 braincase… merit its assignment to Homo and preclude its affiliation with two species of Homo living on the continent at the time (H. rudolfensis and H. habilis). H. erectus has a distinctly shaped [braincase] compared with other early Homo species and one that is present even in young individuals; on this basis, the authors recognized DNH 134 as [H. erectus].
Another important aspect of this research (I told you there was lots to unpack) was the discovery of stone and bone tools dating back to the same time period. So at roughly 2 million years old, they’re now the oldest tools ever found in southern Africa. Older tools have been found elsewhere, including 2.4 million-year-old stone tools unearthed in Algeria and 2.6 million-year-old stone tools found in Ethiopia.
As previously mentioned, the presence of three contemporaneous hominin genera was linked to climate shifts happening between 2.3 million and 1.8 million years ago. The hot and humid south African climate was becoming cool and dry, turning forests into savannah grasslands.
For members of Homo, this transition was bearable and even ideal, given our flexible diets and nomadic dispositions. The same could not be said for Paranthropus and Australopithecus, who likely struggled to adapt to the changing environment. As the researchers point out in the new study, these shifts would’ve hit Paranthropus particularly hard as a species that relied heavily upon roots and tubers (Paranthropus individuals were short, with wide teeth designed for grinding tough plant material).
So as Paranthropus and Australopithecus struggled to maintain their existence, the new kids on the block—Homo—filled the void, according to the new research.
The irony of all this is how human-induced climate change now threatens our species, where once it contributed to our ongoing existence. Still, it’s an important lesson, showing the catastrophic impacts a changing climate can bring, even to species that have been around for millennia.