Archaeologists Discover Missing Link in Human Evolution, in Israel

A hominin died in Jordan Valley 1.5 million years ago – and isn’t the same species as the hominins who reached central Asia 1.8 million years ago. Israeli archaeologists prove there were multiple exits from Africa, and by more than one human species

Ruth Schuster
Ruth Schuster
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A top (a), rear (b), bottom (c) and front (d) view of the vertebra discovered at Ubeidiya.
A top (a), rear (b), bottom (c) and front (d) view of the vertebra discovered at Ubeidiya.Credit: Dr. Alon Barash
Ruth Schuster
Ruth Schuster

About 1.5 million years ago, a child died near the Sea of Galilee. All that remains of the youngster is a single bone, a vertebra. But that skeletal fragment, first unearthed in 1966 and only now recognized for what it actually is – the earliest large-bodied hominin found in the Levant – changes the story of human evolution.

Among other things, that one bone proves for the first time that there were multiple exits by archaic humans from Africa. At 1.5 million years of age, the bone is the second-oldest hominin fossil to be found outside Africa. The oldest date to 1.8 million years ago and were found in Dmanisi, Georgia, and that difference of about 300,000 years proves in and of itself that there was more than one exit.

More? This archaic child in the Jordan Valley and the hominins at Dmanisi were not the same species.

The study on the vertebra, which is by far the oldest hominin fossil in Israel, was published Wednesday in Scientific Reports by an international team led by Dr. Alon Barash of the Azrieli Faculty of Medicine of Bar-Ilan University, Prof. Ella Been of Ono Academic College, Prof. Miriam Belmaker of the University of Tulsa, Oklahoma, and Omry Barzilai of the Israel Antiquities Authority.

The site at Ubeidiya.Credit: Dr. Omry Barzilai / Israel Antiquities Authority

Ecce homo?

The story of the bone begins in 1959, when a member of Kibbutz Afikim named Izzy Merimsky was bulldozing land in preparation for agriculture and, Barash explains, suddenly observed that his machine was unearthing human bones, including a skull and teeth.

No, those did not belong to the ancient child. We don’t know what they were because they were hopelessly out of archaeological context, Barash explains. They could be incredibly ancient or from some recent local flare-up. Maybe one day that will be cleared up.

Anyway, being archaeologically aware, Merimsky called in the authorities. Excavation began in 1960 and it became clear that the site was deeply prehistoric. Subsequently, in 1966, the archaeologist Moshe Stekelis unearthed the vertebra in situ that would change the story of human evolution. But not right away.

Said vertebra had been found with animal bones. “For some reason,” Barash says, “it was placed in a box marked ‘Homo?’ – with the question mark – and forgotten. It was ignored. It was put with monkey bones.”

Moving onto the 2020s and University of Tulsa paleoanthropologist Miriam Belmaker, who was working with the Antiquities Authority’s Barzilai on reconstructing the paleoclimate at prehistoric Ubeidiya, and embarking on the tortuous process of trying to date the site with accuracy. “It’s a work in process,” Barash observes.

In the hope of resolving the dating conundrum, Belmaker reanalyzed all the animal fossils found at the site, which are indicative of climate. (If a tropical animal is found, the area wasn’t glaciated, to be extreme about it.) She rediscovered that backbone bit, suspected it was not a monkey, and called in Barash the paleoanthropologist, Barzilai relates. One look sufficed for Barash to know that an ape, it was not.

Homo erectusCredit: Henry Gilbert and Kathy Schick

That look was followed by a vast amount of comparative research on the vertebrae of ancient hominins, modern humans, hyenas, rhinos, lions, apes and other animal suspects that had all been present in Ubeidiya, say Barash and Ono College's Prof. Been. And this is what they found.

“It was not an australopithecine and not an elephant and not a gorilla and not a mermaid – we measured a ton of vertebrae. It has distinct features. It was a large-bodied bipedal hominin,” Barash says.

Even before the vertebra resurfaced and was reclassified as a fragment not of monkey or merperson but of extremely ancient hominin, Ubeidiya had been believed to date back to 1.5 million years, based on stone tools unearthed there thanks to that observant kibbutznik who just meant to clear land to grow something or other, Barzilai says.

Analysis of the bone was done with Been, an expert on paleoanthropology who explains that having thoroughly studied the vertebrae of every animal that moved in Ubeidiya at the time, and decided it was a hominin, they then considered what part of the hominin’s back it came from. Morphometric analysis showed the bone was one of the lower three lumbar vertebrae.

“In bipeds, these vertebrae have a unique structure,” Been explains. “The anterior part is tall and posterior part short” (because in bipeds, the lower back is load-bearing). “In this one, the anterior part was tall and the posterior part was short, which we don’t see in monkeys or apes, which are not bipedal.”

The question is, which hominin was this child? One hint lies in the tools found at Ubeidiya, which were classified as relatively advanced Acheulean-type, not primitive Oldowan – which is hugely significant. (Yes, there were extremely primitive stone tools as much as 3.3 million years ago, but we have no idea who the toolmaker was, Barash points out, and shall leave that out of our story.)

Omry Barzilai from the Antiquities Authority.Credit: Miri Bar, Israel Antiquities Authority

Confusion in the Caucasus

It is believed that the Homo line (culminating in us) split from the Pan line (culminating in the chimpanzee) 7 million to 6 million years ago. Until recently it was thought that after the split, human evolution was linear.

It was not. We now realize there were multiple types of hominins, some living contemporaneously with one another and, as of 2 million years ago at least, roaming out of Africa.

The oldest hominin fossils found to date outside Africa are just over 1.8 million years old, in Dmanisi; and now we have this individual from 1.5 million years ago in Israel. So, first of all, clearly there was more than one hominin migration out of Africa. There could have been dozens, there could have been constant creep, in both directions – we simply don’t know. The fossil evidence of our prehistory is incredibly sparse and stone tools can only tell us so much.

We also can’t say how many hominin species there were in Africa when the ancestors of the Dmanisi crew exited. But among the earliest members of the Homo line in Africa was Homo habilis, which lived from perhaps 2.3 million to 1.6 million years ago. And following on its very heels, we find a new species – Homo erectus, – Barash explains.

The chimp brain is about 300 to 400 cubic centimeters in volume. Australopithecus was no larger than a chimp and had only a slightly bigger brain: perhaps about 450 cc. In other words, no great difference. Australopithecines were weeny, too, with the famed Lucy estimated to have been a meter tall (3 feet, 3 inches). Some think maybe 1.20 meters, which is still wee. Still no great distance from the chimp.

Homo habilis was a step along, with a brain about 600 to 700 cc. in volume but was also short, a few centimeters taller than Lucy. Then come the next species: erectus was a giant, relatively to its predecessors. It was beefier and taller, with a bigger brain, about 800 to 900 cc, Barash explains.

A skull of Homo habilis.Credit: Rama

In addition, Homo habilis in Africa was found in association with the primitive, early Oldowan-type tools. Homo erectus in Africa was found in association with more advanced Acheulean-type tools: hand-axes, choppers and the like.

Now for a twist. Who exactly was found at Dmanisi?

Good question. The Georgian authorities simply deflected any classification enigmas by dubbing their being Homo georgicus. Many simply assume it was a variant of erectus. But in fact they were small-bodied and had small brains, Barzilai points out.

Reconstruction of Homo georgicus showed them to be much shorter than erectus, he observes. Moreover, the stone tool culture found there is primitive Oldowan-type, not advanced Acheulean.

Yes, the team suspects that Dmanisi Person, aka Homo georgicus, arose from Homo habilis expanding out of Africa around 2 million years ago and reaching central Asia and perhaps beyond. Though while about it, Barash makes things even messier: there is no consensus that the creatures at Dmanisi belonged to a single species, he says.

“The bottom line is that georgicus were definitely not Homo erectus,” he says. “For one thing, their brains were too small. If you took the Dmanisi skulls and put them in an African context, you would clearly see – it’s habilis.”

Fine. How the habilis or whoever it was got to Dmanisi, we do not know. Israel and the Levant are the natural land bridge between Africa and Eurasia, but no fossil hominin bones from that deep prehistory have ever been found in Israel or anywhere in the Levant. Nor have sites that could be 2 million to 1.8 million years old, going by tools. Which doesn’t necessarily mean habilis didn’t pass through here 2 million to 1.8 million years ago, just that we haven’t found the evidence.

A skull of Homo erectus.Credit: Tiia Monto

But now, from 1.5 million years ago, associated with relatively advanced Acheulean-type hand axes, Israel has a bone. Whose bone? Erectus’ bone.

“It certainly belonged to erectus,” Barash states.

Let us be clear that this momentous discovery does not make our lineage any clearer. If anything, it’s muddier. We cannot say that habilis begat erectus which begat hominin races in Europe such as the Neanderthal. We have absolutely no idea which if any of these species were our ancestors.

But we can say that because Ubeidiya is 1.5 million years old and the tools are Acheulean, the person there was from a separate migration wave than the ones who wound up in the Caucasus.

One wonders why everybody and his dog assumes the Dmanisi specimens were erectus and are not commonly identified as habilis.

“Erectus used to be the waste basket – everything from 1.5 million years onward was called erectus,” Barash sniffs. Nowadays, the fashion is to split them: Homo ergaster, Homo antecessor, and so on. The rub is that actual evidence is beyond scarce. There are perhaps one or two samples of each, which is hardly enough to base speciation on; and may we note the vast variation that can exist within a species. (Pygmy versus Norwegian – need we say more?)

But Barash is sure that Ubeidiya Person is an erectus type. For one thing, despite being a child it would have been huge – not like the weedy, ape-like habilis that maybe would have weighed 30 to 40 kilograms (66 to 88 pounds) in adulthood and reached your waist. The only complete erectus skeleton ever found, in Kenya, was 1.8 meters (6 feet) tall – and it was young. This one in Israel would have been that tall too if it had survived to adulthood, the archaeologists estimate.

Dr. Alon Barash from Azrieli Faculty of Medicine at Bar-Ilan University, Ramat Gan.Credit: Dr. Alon Barash

Prof. Been for one thinks its final height would have been more than 1.8 meters tall, which is their conservative estimate. It was big, and if anything bigger than the African erectuses, she says.

he died young

So there were multiple waves out of Africa; habilis and erectus, and who knows who else. Asked apropos of nothing for his opinion about the tiny small-brained “hobbits” of Southeast Asia, Homo floresiensis and Homo luzonensis, Barash doesn’t completely dismiss the possibility that they really did arise from a super-primitive species like Australopithecus who might have left Africa even earlier. However, he suspects they arose from habilises or erectuses that reached the region, and underwent dwarfism on the islands. Sapiens they were not.

Now back to northern Israel and that vertebra. Morphologically it was biped-type and hailed from the lower back, aka the lumbar region. And the being was big (“large-bodied”), Barash says.

How do they know 1.5 million years after the event, from a single bone, that it came from a juvenile? It hadn’t finished growing. Ossification was not complete.

The site at Ubeidiya where the vertebra was discovered in 1966.Credit: Emil Alagem/Israel Antiquities Authority
A 1.5 million-year-old flint cutting tool found in Ubeidiya.Credit: Dafna Gazit/Israel Antiquities Authority

In modern humans, the last bone to finish ossifying is the pelvis, at about age 25, he explains. The vertebrae ossify at about age 3 to 4. This vertebra was not completely ossified, so it came from a child. They think it may have weighed between 45 to 50 kilograms at death.

This particular one is estimated to have been aged somewhere between 6 and 12, but we don’t know how its species grew, he qualifies.

“Modern humans grow very fast from birth to age 3-4, then we grow more slowly, and then in adolescence we have another growth spurt. No other animal does that,” Barash explains. “We think Neanderthals also grew linearly. We suspect that here too.”

Based on extrapolation, they believe the child would have reached a considerable 1.8 meters in adulthood. Yes, that’s classic erectus territory and completely different from what we know from Dmanisi. Going by chimp standards, it could have towered to 1.92 meters in adulthood, the team adds.

Been also shares a personal story – how she became involved in the research. “I was born just 2.5 kilometers from Ubeidiya, in Kibbutz Alumot. When I was a small child, 3 or 4, my grandfather Moshe Zoref would pick up flint tools in the fields which could have been made by erectus! He would make knives out of them, using animal jawbones. He taught me how to use them and would tell me about ancient hominins. For me, this project was closing a circle,” she says.

So, what do we have? A child from a very large species of hominin, who in dying in northern Israel 1.5 million years ago provided the first proof that more than one species left Africa in multiple waves over 200,000 to 300,000 years.

The site at Ubeidiya in northern Israel.Credit: Dr. Alon Barash

And then what happened, after habilis and erectus and who knows who else left Africa? We have no idea.

“Were there other waves before or after? We don’t know. We find elephants – maybe they followed the elephants to hunt them,” Barash says, going straight into the territory of his colleague at Tel Aviv University, Prof. Ran Barkai, who believes human evolution has close ties with our appetite for elephant.

Barash continues to throw little bombshells into this boiling pot of evolutionary spaghetti. Maybe the erectus and habilis met and interbred in Europe, he speculates for fun. And asked to confirm that, indeed, we have no indication that either of them are ancestral to us, he confirms it.

He also adds: we sapiens never were massive. We are a gracile lot, while the erectus and its ilk (and Neanderthals) were not only tall but burly. It is entirely possible that with all the recent discoveries and all the insights, we never have found our ancestor.

The site at Ubeidiya in northern Israel.
A top (a), rear (b), bottom (c) and front (d) view of the vertebra discovered at Ubeidiya.
A skull of Homo habilis.
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The site at Ubeidiya in northern Israel.Credit: Dr. Alon Barash
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A top (a), rear (b), bottom (c) and front (d) view of the vertebra discovered at Ubeidiya.Credit: Dr. Alon Barash
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A skull of Homo habilis.Credit: Rama
Missing link

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