A Two-Million-Year-Old Fossil Has Totally Overturned What We Know About Our Human Ancestors

It’s 2015, and Richard Curtis uncovers a bone fragment at an archeological site in South Africa. He thinks it’s probably nothing more exciting than the remains of a baboon. Two colleagues, Jesse Martin and Angeline Leece, examine the fragment and 150 others from the site and attempt a reconstruction. And what they ultimately finish up with transforms our understanding of human evolution.

The researchers from La Trobe University in Melbourne, Australia were excavating a South African site called the Drimolen Palaeocave System. It’s one of the most important archeological sites in the world, renowned for yielding outstanding examples of human ancestors from deep time. Set around 25 miles north of the city of Johannesburg, it’s a magnet for paleontologists.

The Drimolen Caves, which over the millennia have lost their roofs to erosion, are very special indeed and that’s why they were declared as a UNESCO World Heritage in 1999. What’s more, they were given the dramatic title “Cradle of Humankind.” The late Andre Keyser, a distinguished South African paleontologist who died in 2010, discovered the site in 1992. The limestone caves sprawl over an area of around 180 square miles.

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We’ll get back to the 2015 discovery we described earlier, but first let’s hear about an earlier find at Drimolen. We’ll also explore some of the earliest origins of our own species, Homo sapiens. Indeed, over the years, there have been some extraordinary discoveries at this South African site. One in particular, relating to the evolution of humankind, came in 1994.

In that year Keyser unearthed two fossil skulls of a human precursor called Paranthropus robustus. One, a female, was designated DNH 7; the other, a male, was dubbed PNH 8. Rather more romantically, Keyser nicknamed the skulls Eurydice and Orpheus after two ill-starred lovers from Greek mythology. He did that because the Greek character “came from the underworld.”

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Between 1.5 million and two million years old, the skulls were judged at the time to be some of the oldest examples of hominins ever found. Hominin is the name for the group of animals that includes all extinct human species as well as modern humans. Paranthropus is an extinct species, having died out about 600,000 years ago, after inhabiting the planet for around a million years. Modern people are the only hominin species now living.

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Speaking to the BBC in 2000, Lee Berger of Johannesburg’s Witwatersrand University explained the status of Paranthropus, “They are not direct ancestors of modern humans but are more like ‘kissing cousins’ of our ancestors.” Eurydice’s bones found at Drimolen consisted of a partial skull and teeth dating from 1.5 million to two million years ago. All that was left of Orpheus was a jawbone, which also had teeth.

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Keyser described the moment of discovery to South African newspaper the Mail & Guardian in 2000. He said that he had been working with some amateurs in 1994 when one of them had uncovered something that had looked interesting. Keyser continued, “I took over immediately, brushed the soft soil carefully from around it, and there was the outline of a beautiful skull and its mandible, perfectly preserved.”

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Keyser added, “Not far from the skull, we found an enormous lower jaw with huge teeth.” That was Orpheus, the male. And the paleontologist explained, “We don’t expect they knew each other in real life, of course, because these fossils were washed down from deposits in an upper cave, but we like to think that maybe they might have loved each other many generations apart. Now we’ve had the privilege of bringing them to the surface at last.”

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Paranthropus is an interesting species in its own right since it’s at least adjacent to the evolution of our own species, Homo sapiens. What’s more, as Keyser told The New York Times in 2000, “They represent a creature that was in direct competition with our earliest ancestors.” Those direct human ancestors most notably included Homo erectus. That Latin name means “upright man.”

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Talking to British newspaper The Guardian in April 2020, paleontologist Andy Herries highlighted the fact that the exact lineage of human evolution is a hotly debated topic. However, he shared one point of consensus relating to Homo erectus. He said that there was agreement, “This [species] is the beginning of us; this is the beginning of our genus.” So Homo erectus is a key species in the human story.

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And Homo erectus has one key difference from Paranthropus. The latter’s remains have been found only in Africa, whereas fossils of Home erectus have been found as far afield as modern Spain and Java, an island that’s part of modern Indonesia. Members of the species in Africa are believed to be the ancestors of various human species including the Neanderthals and ourselves.

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Homo erectus is the oldest human species we know of whose body ship was akin to our own. Their legs were relatively long compared to the size of their torsos, just like us. Scientists believe this may have been a result of our ape-like ancestors forsaking an existence in trees. Coming down from the heights of the forest, our ancestors began to live on the ground. And they became the first species we are aware of to walk properly upright.

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Once these early human predecessors were living on the ground, long limbs would have been an advantage for running. Being able to run, perhaps for long distances, would have been helpful for hunting. Homo erectus had another important physical characteristic that distinguished them from their ancestors: a larger brain case.

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The brain size of Homo erectus continued to increase over time, and with that came a range of behaviors that we can recognize as human. Homo erectus made tools from stone, is the first species known to us that had mastered the use of fire and lived together in organized groups. These small communities were capable of coordinating hunting and gathering. These primitive humans may even have created art.

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Whether Homo erectus had developed speech is the subject of continuing debate, but they may have had some means of communicating with each other. One thing we do know is that the species was on the planet for a lot longer than we have been. They were around for around two million years, whereas we’ve only managed something like 300,000 years so far.

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The first remains of Homo erectus were found not in Africa as you might expect but on Java back in the early 1890s. Dubbed Java Man, this Homo erectus fossil specimen has been dated to between 700,000 and one million years old. At the time, this was the oldest evidence of ancient humans ever discovered.

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A team led by a Frenchman, Eugène Dubois, made this momentous discovery. The researchers uncovered the top of a skull, a femur and a tooth. The discovery would lead to years of controversy. Dubois argued that he’d found a transitional species from ape to man, but many others disagreed with his theory.

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Java has also been the source of Homo erectus fossils of the most recent age ever found. In the years from 1931 to 1933, a Dutch-German paleontologist called Gustav von Koenigswald found the ancient bones along the banks of the Solo River. These fossils were between 108,000 and 116,000 years old, making them the latest known examples of Homo erectus remains.

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The bones soon took the name of Solo Man, and they show that there were different human species existing at the same time. Indeed it may be the case that Solo Man existed alongside our own species although this has not been confirmed. In fact, at first scientists thought Solo Man was a subspecies of Homo sapiens, but this was later regarded as wrong.

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So Java produced the most recent specimens of Home erectus. But that leaves the question of when exactly this ancient human species first walked the Earth. One famous find with very early dates came near Kenya’s Lake Turkana. Inevitably named Turkana Boy, these fossil remains are the most complete skeleton of a Homo erectus ever found.

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Researcher Kamoya Kimeu came across Turkana Boy’s bones in 1984 on the banks of the Nariokotome River. The boy lived around 1.5 million to 1.6 million years ago and was between seven and 11 years old when he died. This find clearly showed how much earlier Homo erectus was alive than our own species. But archeologists are continually finding more specimens, and the earliest dates of Homo erectus can be pushed back by just one new discovery, as we’ll see.

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And that brings us back to the team we met earlier, who were excavating at the South African Drimolen site. The dig was an international operation with participants from South Africa’s La Trobe University and Washington University in St. Louis, Missouri. As we mentioned, the first discovery was of a small fragment of bone buried in the ground at Drimolen.

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It was Richard Curtis, a graduate student at La Trobe, who found that initial piece of bone – on his very first dig. Eventually, the excavators had a collection of 150 bone fragments. In fact these were pieces of skull. At first, it was thought that they were from the cranium of a baboon. But one of the researchers had her doubts about the baboon theory.

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She was Stephanie Baker of the University of Johannesburg, the woman who is responsible for the overall management of the Drimolen site. Speaking to The New York Times in April 2020, she recalled, “These beautiful bits and pieces of crania started coming up.” And she decided to examine these mysterious bone fragments more closely.

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One evening the Drimolen researchers were attending a lecture and Baker took the opportunity to find a quiet spot at the back of the room. There she started to manipulate two of the bone fragments. It was like trying to solve a complicated three-dimensional puzzle. But eventually, the pieces fitted together perfectly.

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Baker immediately realized that she had bones not from a baboon but from a hominin in her hands. But from which ancient human species did the skull fragments come from? That was far from clear. So two other researchers from La Trobe took over the investigation of the bone pieces. They were Jesse Martin and Angeline Leece.

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Leece and Martin had the tricky task of trying to make some structural sense of the 150 or so fragments of bone. But first they had to clean them. In an article on La Trobe University’s website, Leece explained that the bone pieces had been “found in material that was still quite hard and had to be carefully removed to expose the bone fragments.”

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Martin is the man people go to when there are multiple pieces of bone to assemble. He and Leece, who are married, had to exercise extraordinary discipline as they pieced the fragile fragments together. They had to spend prolonged periods not talking and scarcely breathing. The slightest disturbance could have upset the painstaking process of assembling the bones.

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Martin has said that he’s especially suited to this type of work because of a childhood accident. That left him with a loss of feeling in his left arm, which means that he can hold it in one position for lengthy periods. Talking about their work, Leece told The New York Times, “It’s nerve-racking; my heart goes every time.” While Martin quipped, “We’re a couple that is clearly comfortable with awkward silences.”

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The specimen now had a name, DNH 134, and the shape of the skull that they were recreating became apparent. The cranium had a crest of bone running along its length and that pointed to one conclusion. This skull had belonged to a member of the Homo erectus species. Quoted in an April 2020 news article on the University of Johannesburg website, Baker described the process of confirming that this was indeed Homo erectus.

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Baker explained, “This find really challenged us. We compared the assembled skullcap to all of the other examples of hominins in the Cradle area. Eventually, its teardrop shape and relatively big brain cavity meant we were looking at Homo erectus.” However, this had been far from a long-lived individual. Reece and Martin estimated that the skull’s owner had died at the age of perhaps three.

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But the real significance of this discovery of a Homo erectus individual at the Drimolen site was the age of the skull. The scientists used a range of high-tech methods to determine the age of the specimen. And the answer they got astonished them. The DNH 134 skull was between 1.95 million and just over two million years old.

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And that figure means that DHN 134 is the oldest specimen of Homo erectus that’s ever been found. The previous oldest one was discovered in a place called Dmanisi in the modern country of Georgia which is located at the boundary between Europe and Asia. The specimen found there was around 1.8 million years old, between 150,000 and 200,000 years more recent than the Drimolen find.

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And there were further implications from this dating of DHN 134. The method used had actually dated the material in the Drimolen cave. Baker pointed out, “We collated all of the dates from each of these techniques and together they showed that we had a very precise age. We now know that the Drimolen Main Quarry and all of the fossils in it, are dated from 2.04 [million] to 1.95 million years ago.”

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And that means that the fossils of Paranthropus robustus found in the quarry in 1994 are the same age as the Homo erectus skull. What’s more, it means that the two species of ancient hominin were living at the same time in the same environment. In fact, there were not two but three species of ancient humans living in southern Africa two million years ago.

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The third species was Australopithecus, which lived in Africa from around four million years ago until 1.9 million years ago. All three species became extinct, but most scientists are agreed that Homo sapiens evolved from Homo erectus, making it an especially important ancient ancestor for us humans. And we now know that for a time the three different species coexisted.

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Previously, some scientists wondered if Homo erectus might actually have originated outside of Africa since the oldest-known fossil of the species was from Georgia. But this most recent find in South Africa seems to confirm Drimolen’s status as the Cradle of Humanity, and of our direct ancestor Homo erectus. At least until the next startling fossil find.

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Speaking to The Guardian in April 2020, Professor Andy Herries, head of the research team that discovered DHN 134, said, “It’s so exciting, because our fascination with human evolution is because it’s the story of us, and when we go back this far with a discovery like this, it’s the story of every person living on the planet. The group this two- or three-year-old was a part of could have been the origin of everyone alive today.”

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Homo erectus lived on the planet, and spread across it, for some two million years. As we mentioned previously, that’s a far longer span than Homo sapiens has been around. And in an email to National Geographic in April 2020 New York University paleoanthropologist Susan Antón offered a sobering thought. She wrote, “Homo sapiens may be more abundant right now than Homo erectus has ever been. But will we last for as long? Only time will tell.”

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