Neanderthal tooth in Iran from 42,000 years ago redraws human evolution

Read More

Around 42,000 years ago, there were Neanderthals in Iran. We know this because archaeologists have found a Neanderthal milk tooth in a rock shelter called Bawa Yawan in Iran’s towering Zagros Mountains.

This tooth belonged to one of the last Neanderthals in the world. Being a milk tooth, it could have come from a toddler who died and whose other bones have disappeared, or it could have fallen out of the mouth of a perfectly healthy child whose adult teeth were coming in. Its root is gone.

The tooth, an eyetooth, was found near tools typical of the Mousterian culture in the Zagros. That isn’t proof of a Neanderthal presence per se: Mousterian utensils have been associated with both them and early Homo sapiens.

In addition, anatomically modern humans were also in the Middle East at the time and had been for thousands of years, says the team, led by Saman Heydari-Guran, head of the Neanderthal Museum in Hochdahl, Germany, and Jean-Jacques Hublin, director of the Department of Human Evolution at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

In other words, this tooth adds to other evidence that Neanderthals and sapiens lived cheek by jowl for thousands of years.

Which begs the question: How confident are the researchers that the tooth belonged to a Neanderthal and not a young sapiens? “Neanderthals are quite distinctive in their morphology, especially dental morphology,” Hublin explains.

To Hublin, teeth are nice, but he says the most interesting thing about the discovery is that Neanderthals were in Iran around 42,000 years ago. This single tooth tells a very long story, debunking the wildly oversimplistic view that along came Homo sapiens and replaced the Neanderthal.

Paradigm shift in human evolution: Early humans left Africa via Arabia

Indigenous group in Philippines has highest Denisovan ancestry in the world

Neanderthals boiled and carved a deer bone 51,000 years ago, archaeologists say

No, the Middle East and Israel weren’t some kind of gateway through which Homo sapiens barged and put paid to our cousins.

“The peopling of Eurasia by our species was a much longer, more complex process than we envisioned,” Hublin says.

The Zagros Mountains in Iran, peopled by Neanderthals well after sapiens spread to EurasiaVah.hem

Yes, this process did ultimately culminate in that one great expansion of sapiens out of Africa that did, once and for all, supplant the Neanderthals and the Denisovans and the devil knows who else. But for thousands and thousands of years, we begin to realize, in Eurasia and the Middle East, sapiens and other species overlapped.

To put the Iranian Neanderthal discovery in a broader context, Homo sapiens lived in Bulgaria, in Bacho Kiro Cave, 46,000 years ago, and in Zlaty Kun, Czech Republic, 45,000 years ago. There too one single tooth changed everything we know.

And now we know there were still Neanderthals in Iran 42,000 years ago, Hublin notes – which, he confesses, blows his mind.

Recently obtained genetic data also proves overlaps in time and space between Neanderthals and Neanderthal-like Denisovans. All three species could and did go very, very far, expanding thousands of kilometers.

But these weren’t like the seasonal migration of the wildebeest, featuring millions of animals, mind you. These Homo “migrations” consisted of small bands moseying along.

In short, the pattern of peopling Eurasia was a mosaic that featured a lot of dispersal and a lot of local extinction, Hublin says. Some patches of Eurasia may have hosted all three species; some had none. “Each group in each region had its own fate,” he adds – and that applied to Homo sapiens too.

As DNA analysis reveals, the Bulgarian sapiens interbred with Neanderthals a couple of generations earlier. They all had locally inherited Neanderthal DNA on top of the initial ancient introgression, or entry, of Neanderthal DNA (which happened in the Levant, Hublin says). These proto-Bulgarians don’t seem to have left descendants.

A sapiens woman in the Czech Republic, who seems to have been subjected to a hyena, didn’t have local Neanderthal DNA, only the signals from a much older introgression, the Max Planck professor says.

“The big picture is that at least for that time period, we have pioneer groups expanding in the midlatitudes that were probably mostly replaced later by another wave of Homo sapiens that somehow was more successful,” Hublin says. “Even at short distances we have groups with different stories, and all disappeared. In a couple of millennia they were replaced by others.”

So the story of human evolution is looking less like a linear progression and more like spaghetti carbonara, leaving raw egg on our superior faces.

A tooth belonging to one of the last Neanderthals in the world, found in Iran’s Zagros Mountains.IRNA

Footloose and fancy very free

In their heyday, Neanderthals thronged Western Europe and large swaths of Asia, ice sheet constraints permitting; Denisovans dwelled in Eastern Asia. Their ancestor split from sapiens’ ancestor in Africa possibly about 700,000 years ago; then in Eurasia or the Middle East, their ancestor split into Neanderthals and Denisovans.

Sapiens began pushing out into the Middle East and Eurasia at least 200,000 years ago and probably more. The early exiters seem to have mixed with other hominins and left traces in their genomes, but no Eurasian lineage of sapiens endured. Israel has early sapiens remains (for example at Qafzeh and Skhul) dating to about 100,000 years ago – whispers of a failed exit.

Then came the great sapiens surge, spreading out of Africa through the Middle East, that begat all non-African humans alive today.

The timing of that “successful” exit is controversial. If one believes the hypothesis that Australia was peopled as much as 65,000 years ago based on the evidence from Madjedbebe in the north of the continent, this dates the “successful” exit to, say, 70,000 years.

Excavating at Bawa Yawan, 2017Sfandiari

But the Madjedbebe story is hotly disputed. In a piece penned for the journal PNAS this year, Hublin presents the state of the evidence and concludes: “One can speculate that our species possibly reached east Asia before 55,000 or 50,000 years ago but maybe not much before.”

This fits with the theory of Prof. Israel Hershkovitz from Tel Aviv University that Neanderthals spread from Eurasia to the Levant and Middle East about 70,000 years ago, and in Israel at least, died out about 50,000 years ago, about the time they encountered modern humans.

Hershkovitz also notes that the Neanderthals in the Middle East, such as the ones who may or may not have buried their dead with flowers in Iraq’s Shanidar Cave, or the ones whose remains are found at Kebara and Amud in Israel, were a subcategory known as “eastern Neanderthals.” They were not identical to “western Neanderthals.” The eastern ones were taller and rangier and sported less of a prominent brow ridge. This variation is hardly a surprise. Just look at the variation in today’s humans.

The bottom line is that in southern Europe, and in the Middle East, Neanderthals and these humans overlapped for thousands of years. Were they friends? Heaven knows. But they did interbreed.

Denisovans aren’t known to have reached the Middle East, though they may have; the fact is, for a species so (apparently) wildly successful, all we have are some isolated bones found in Siberia’s famed Denisova Cave and a jawbone in Tibet.

Some bones found in China, including of the “Dragon Man,” could be Denisovan too but their DNA is unretrievable. So it goes.

The Zagros Mountains; most of the range is in Iran. Joshua Doubek

The Iranian Neanderthal

And now we have a Neanderthal’s milk tooth in an Iranian site in the Zagros Mountains dating to about 42,000 years ago; this child would have belonged to one of the last Neanderthal populations in the world, surviving thousands of years after the great sapiens surge into the midlatitudes of Eurasia, and after their kinfolk back in Eurasia had died out.

Just as sapiens ventured into Eurasia more than once, Neanderthals ventured south into the Levant and Middle East more than once. Their final adventure southward began about 80,000 years ago.

“We know that Neanderthals were there [in Israel] even before the sapiens at Qafzeh, near Haifa and more,” Hublin says. In fact, looking at Israel, we find sapiens then Neanderthals then sapiens again then Neanderthals again – as well as hybrids. And finally there are sapiens everywhere and Neanderthals nowhere.

“My view is that what we have is a border zone, and the border was moving,” he says.

It wasn’t like a today-border marked with barbed wire or even a mud-brick wall. This heaving, broad, moving undemarcated border zone lasted for many thousands of years, even hundreds of thousands of years. One result was regular hybridization between the two groups, which could explain some of the “weird” features observed on fossil hominins found in Israel, Hublin suggests.

Weird? How about this – there is genetic evidence of introgression from ancestral sapiens in Africa into Neanderthals possibly as long as 350,000 years ago (or as late as 150,000 years ago), but in any case, after Neanderthals and Denisovans split. What’s that evidence? It’s that the Y chromosome in the Neanderthal is like that of sapiens, not that of their sister species, the Denisovan.

Ditto the mitochondrial DNA. The Neanderthals’ version is closer to ancestral sapiens than to Denisovans.

Weird? How about a host of remains claimed to be early sapiens in India, China and Asia in general, though those remain “poorly substantiated,” Hublin notes.

What are we to make of all this? That the postulated “border area” between Neanderthals and sapiens existed for a very, very long time, Hublin says. Given the incessant wanderlust of sapienskind and seemingly every homininkind, this likely happened every time Arabia and the Sahara greened. He notes that these migrators would happily move into any convenient ecological niche – they weren’t thinking “Oh, let’s migrate to France.”

Anyway, possibly intermittent but long-term interaction between sapienskind and Neanderthalkind would also explain why they basically made the same sort of stone tools, though researchers today are at pains to figure out which species made which tools, Hublin adds.

“It’s clear that there is a local Levantine Mousterian technology, made indifferently by Neanderthals and by Homo sapiens,” he says. In any case, the replacement didn’t happen in one swoop, it was a long, complex process.

The sapiens breakthrough that overcame all odds and sundry Homos was different. It seems our species prowled southern Eurasia on and off for much longer than has been thought. But the new guys forged onto the highest latitudes. And that seems to be down to major cultural and material change.

And Hublin has a prediction: As more evidence comes to light, we’ll find more ancient populations sharing the same kind of culture, somehow.