Where to meet a Neanderthal
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We know this story because it is written in our genes. Some people owe around 2% of their DNA to Neanderthals. But it's hardly a complete story, right? It's honestly more like an opening sentence. We would still like to know...

What was the relationship dynamic here, right? Like, was there any cuddling after all this early modern coitus? Did Neanderthals and early Homo sapiens, I don't know, smooch? This is the thing. We really have no idea at all what those interactions looked like. Adam Cole is the co-host of Howtown, a science show I love a lot, where they dig into how scientists know what they know.

And in a recent episode, he went very deep into our Neanderthal ancestry and found lots of promising genetic research, but not so much direct archaeological proof of Neanderthal relationships with Homo sapiens of yore. We don't have any evidence of these romantic couplings. You know, ideally, you'd want to find like a grave where two people were holding hands and one of them had like slightly...

And it's not just that we're missing key details about Neanderthals and early humans' most intimate moments.

We're also missing details about all of their shared moments, like sexual or otherwise. There's not a sign of some battle between these two groups. There's no archaeological evidence that directly ties them. Researchers have pieced together some ideas about where and when Neanderthals and humans might have overlapped, but the ranges can be pretty broad. So not a specific site and a specific year.

You know, it's like they were in the same like mountain range in this like 4,000 year period. So it's not exactly conclusive. I was in the same mountain range as Thomas Jefferson, but that doesn't mean that we met. Basically, there's a massive gap here. Like the most basic information about how our ancestors got together is missing. And yet, even though there is no direct evidence of a meetup, some researchers have started to build evidence

a more indirect case. I got very excited because there's a recent paper that for the first time ever managed to sort of piece together some clues to say, here's a place and a time where Neanderthals and Homo sapiens crossed paths. And the way that they pieced this together was through three different clues. There was a baby tooth. There was a bunch of stone blades.

And there was, most remarkably to me, essentially fossilized smoke. This is Unexplainable. I'm Bird Pinkerton. And today on the show, Adam tells us how a tooth, some tools, and some smoke could help researchers put Neanderthals and early humans in the same place at almost the same time. So.

Let's start with the basics. What is a Neanderthal? Also, how do you pronounce Neanderthal? I mean, it's, it's, I've always said Neanderthal and I stubbornly stuck to that. And all the researchers I talked to said Neanderthal. But then when I asked them, should I be saying Neanderthal? They said, I don't care. Whatever you call them, they were a population of humans that diverged from our Homo sapien ancestors many hundreds of thousands of years ago. And then they

Tens of thousands of years ago, they died out. And so there's sort of a different flavor of humanity, I think is the best way to describe it. They used to be thought of as a different species. Now there's a lot of acknowledgement that there's not very hard barriers between these different groups. They were similar enough to our ancestors to reproduce with them, after all.

Still, there were some noticeable things setting Neanderthals apart from Homo sapiens. Like, one of the first things that people noticed when they started looking at Neanderthal skulls in the 1800s was that their heads were very weirdly shaped. If humans have sort of a basketball head, we have a big sort of round dome. Neanderthals have more of an American football head. It's sort of elongated and a little bit lower.

And then... Like, hey, Arnold. Move it, football head. Well, not no. The elongation is from the front to back, not side to side. Overall, Neanderthals had kind of bigger brows. Their rib cages were more barrel-shaped. And they were kind of stockier than Homo sapiens. So again, different. But not that different. There's been a lot of speculation. Like, if you saw a Neanderthal walking down the street and they were wearing normal clothes...

It would be not immediately apparent if you're not really looking for it, I think. You'd honestly probably be more thrown if you saw Hey Arnold walking down the street. Very true. So these stocky football headed people were wandering around parts of Europe and Asia tens of thousands of years ago. They left fossilized bones and tools and other traces of their lives in various caves and other sites.

including at the site that is very important to our story, this cave-like rock shelter by the Rhone Valley called the Grotte Montagne. It's a little outcrop of rock amongst a bunch of foliage. And so you can imagine that tens of thousands of years ago, this would be a good place to hang out, look out, make sure your enemies weren't coming, or more likely that you could see some deer, you know, you could keep a lookout from this little overhang.

And starting in the 1960s, people found evidence that prehistoric people had, in fact, been hanging out in this cave-like overhang. Over the decades, excavators dug at this site, going back in time the further down they went, and they dug through layers of silt and sand and dirt that had kind of blown into the site over time, and then rock that had crumbled down from the ceiling. ♪

Yeah, there's several layers and you can kind of see in pictures of the now heavily excavated site that they're kind of different colors. There's different little colors and textures that sort of define the different layers that came from different events where the silt from sand were deposited. At sites like this, these layers are kind of like a record of the past almost.

It's not a perfect record. Layers can get wiped away by a storm, say. Some years you might get more sediment coming in and some years you might get less. So it's not like each layer is exactly a century or something. But the layers do let researchers work their way back through time. And so in the first layer that they originally excavated—

They were finding lots of signs that this was a spot where bronze era modern humans, so our ancestors, were doing cremation. So this was probably like a special site for funerals. They found, you know, burnt dead bodies, essentially. Just some fun, cheerful stuff. Eventually, the excavators did go deeper, though. And they didn't get too deep before they found...

Teeth that belonged to not Homo sapiens, but Neanderthals.

This is not unheard of. There are other sites in Europe and Asia where you can find both evidence of Homo sapiens and evidence of Neanderthals. There's modern humans somewhere in a shallower layer, so more recent layer. And then deeper down, there might be some Neanderthal remains. There aren't always remains like bones. Sometimes you find Neanderthal pools, for example.

But either way, you have signs of Homo sapiens closer to the top and then signs of Neanderthals as you go deeper. Which is just indicative of sort of the history of these populations where Neanderthals were running around in Europe for hundreds of thousands of years. And then when humans started to show up, they mysteriously disappeared. But at this site in the Rhone Valley, this Grotte Mondrain, they found something unusual.

This paleoanthropologist named Ludovic Svimec was digging at this site along with his team, just kind of excavating. They're going down, you know, layer B, Neanderthal teeth, layer C, Neanderthal teeth, layer D, Neanderthal teeth, layer E. There's just one little baby tooth. It doesn't look like a Neanderthal tooth. It looks a lot more like the modern humans who are living at this time.

And this is kind of a shock to these researchers. This was really the first time that they'd found essentially a Homo sapiens sandwich. Like instead of the layers being Homo sapiens on top and Neanderthal below, you had a Homo sapiens layer, some Neanderthal layers, then another Homo sapiens layer, followed by another Neanderthal layer.

So this would potentially be evidence that there were Neanderthals in the cave for a while, and then Homo sapiens, and then Neanderthals again. Like a trading off that paleoanthropologists had not really seen before. And it would also be evidence that early modern humans were in this part of France way earlier than people expected. So this was a potentially huge find.

But it was also a lot to rest on one single tooth. Some people have reacted to this paper saying, how can we be sure that this is a homo sapien tooth?

The measurements certainly seem to line up, but it's just one piece of evidence. It's one tooth, and this tooth is not like a full, complete... I mean, it looks like a baby tooth when you look at the pictures of it. It looks like, you know, the sort of root has dissolved in the way that baby teeth do. But it's, you know, it's 50,000 years old, and so it's not in pristine shape. And so you wouldn't want to hang your entire thesis on this one tooth.

So these researchers didn't hang their entire thesis on this one tooth. They kept looking, kept exploring this layer sandwich. And in particular, they started looking at some of the other stuff that was in these layers, including, in this case, tools that these people had left behind. Now, Rudavik Stimac has done a lot of work on Paleolithic tools. And he told Adam that if you look at early modern human tools and Neanderthal tools, they

You can really tell them apart. When you look at Homo sapien tools, they're very standardized. They follow a certain pattern, a certain shape. Ludwig told Adam that it's like groups of Homo sapiens came up with one traditional way of doing something and then just kept doing it. And he did say in our interviews, he said, it's rather boring or something like that. Like these are boring tools.

Like, the only thing about the human stuff is it's boring. Neanderthal tools, by contrast, are apparently not boring. Every single one is kind of a flight of fancy. It's a little bit more like, I'm going to try this today. Now, Whimsy is kind of in the eye of the beholder here. Like, these Neanderthal tools are not hot pink arrowheads with googly eyes on the side or anything. Their wackiness is...

You might have to have seen a million of these in order to notice that because I have looked at the pictures. I think some of it is has to do with these minute measurements. Like part of the creativity is the size and shape just varies more in these Neanderthal layers. So I think it's just one of those things where you get to know the subject and you start to see these differences.

The point is that Ludovic Slimac, our heliolithic tool aficionado, along with his colleagues, they looked at the tools at the site. And in the Neanderthal layers, the sort of ones above and below the layer with the potentially homo sapiens baby tooth, they found these somewhat more whimsical Neanderthal tools.

But in the layer with the baby tooth, they found the more standardized, more boring, early modern human-like tools. So this was a further bit of evidence supporting the idea that early modern humans and Neanderthals traded off Occupy in this cave. Maybe. It does seem like...

Many people in this field find these two pieces of evidence pretty compelling, at least to plant the seed that maybe there were modern humans in this part of France at this time. But even if Neanderthals and early modern humans did trade off occupying this cave, that doesn't mean that they came in contact with each other. Right. So, so far we've had the revelation that there was...

an alternation of occupation. So there was Neanderthal, then Homo sapien, then Neanderthal, which was already, whoa, never seen this before. But as you say, that doesn't mean that just because there was this alternation, these two groups were in the same place at the same time. It could have been Neanderthals were living in this rocky outcropping. They left hundreds of years past. Now Homo sapiens come in.

Now they leave. Hundreds of years pass. Neanderthals come back. There's no reason to think just from this initial evidence that they were in the same place at the same time. Which brings us to the third clue. My favorite. That is after the break. Support for Unexplainable comes from Toyota. Some people drive because they've got places to be.

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The sun is in his hands. No, no, it's fire. Ladies and gentlemen of... Unexplainable. I'm just a caveman. Imagine you were living tens of thousands of years ago. You're camping out in this cave-like spot in a river valley, and you decide to make a fire.

So it turns out when you build a fire in this cave, maybe you are just warming yourself up. Maybe you're cooking dinner. Some of the soot drifts up to the ceiling and gets trapped there by minerals that have leached through the rock and are deposited. And so you can have sort of this bit of campfire that's trapped in the rock. A month or two goes by, you make another fire.

The soot drifts up. It gets sealed in place as well. Over and over, you're making fires and little bits of soot are left behind. And then eventually you leave and someone else comes and they also leave little soot signatures behind.

Tens of thousands of years later, when archaeologists find this rock and break it open, they can actually, and this is incredible, they can actually smell that fire. They can smell the wood that was being burned. Sometimes they can smell like a barbecue smell. They can smell some deer ribs being cooked. So you have this incredible, like petrified smoke, essentially. Fossilized smoke.

If that weren't incredible enough, they can actually use this to create a timeline of the occupations of this cave. This is because the mineral deposits that are left on the rock look different in the wet season of each year versus the dry season of each year. So you have...

this alternating pattern that happens on an annual cycle. And so you sort of, just like tree rings, you can see the chronology of years in these rocks. So you can say, oh, this year, this layer of crystals has this little black line that says campfires were being made here. There must have been people around. And maybe there's a couple years where they didn't come back. You know, they're roving around, hunting, and they don't come back for a couple years. There's a little gap there.

Of soot. No soot. And then they come back and there's a new little line of soot. You wind up with this like record book of ancient human activity, basically written in soot and minerals. And then chunks of this sooty record book fall to the floor and get mixed up in the layers along with the teeth and the tools and whatever else.

And one researcher in particular on Ludovic's team, this woman named Sigouline van de Velde, she found that if you look at those sooty rocks under a microscope, you can see the stripy layers in them like a barcode. One rock might have a record of...

not to, you know, a dozen years or something like that. Another chunk might have another 10 years in it with a little bit of overlap with that first rock. And then some third chunk might be another dozen years with no overlap at all. But you get together enough of these rocks and you start to be able to line them up. So all the little barcodes, where they fit in this timeline. And you can put together these little chunks of time until you've got an entire history

history of occupation of this layer. And you can say, okay, they came back here every couple years or every three years or whatever it is. You can learn about the sequence of occupation. So that's already pretty cool because we're now seeing the movement patterns of these people from 50,000 years ago. But it also lets researchers answer this big question they've had about these layers, which is,

If you accept that there were Neanderthals in this cave and then Homo sapiens and then Neanderthals again, did a whole bunch of years pass before those Homo sapiens showed up? Did they miss the Neanderthals completely? Or were they there at almost the same time? The really lucky and incredible thing is that when they created these timelines for layer E, which was the, remember, modern human layer,

And layer F, the layer below it, that was Neanderthals, they have this long barcode. And they look and they see that the ends of these barcodes line up pretty much perfectly. There is an overlap. Which means, potentially... As soon as the Neanderthals left, the humans showed up. And when they looked really closely at those layers, they saw just one year between the two occupations. So...

You know, it could be that maybe there's a couple of years where there's a drought and there's no rainy season or something. But it's enough to say it's within a few years that this alternation happened and possibly one year. So now we've got them. Now it's very exciting. We've got Neanderthals and humans together in the same cave, maybe one year apart. And when you look at those rock tools again...

you can see that they were gathering the rocks for these tools from a pretty wide area, you know, like different kinds of rocks are in different places. So they know, okay, their range was pretty big. And so for these two populations to be inhabiting this large range and alternating within one year, they must have at least seen each other. They must have, one of them must have looked down from that rock shelter and said, oh, there's a group down there of some weird looking people.

football head? And, you know, it's still not not a smoking gun of sorts. It's certainly smoke. And where there's smoke, there's fire, I guess. But, you know, you can't you can't draw too many conclusions. This is certainly not no one's holding this up as evidence of this is the moment when humans and Neanderthals interbred. They're not saying that these people had any sort of, you know, trade of ideas or goods or anything like that.

All they can really say is that maybe, if the interpretation of these bits of evidence is right, maybe Neanderthals and early modern humans were in this one place at very close to the same time. And again, if this paper is right, it would mean that modern humans came out of Africa and into Europe much earlier than researchers thought they did, like 10,000 years earlier.

So the paper is still being debated. Obviously, if you've spent your whole career believing in this one timeline, this evidence that goes against that timeline is met with suspicion. But I will say that to me, who's just encountering all this information for the first time, it makes a lot of sense that there wouldn't be one, you know, definitive evidence

push out of Africa. That was just a continuous march that modern Homo sapiens made from Africa and then around the rest of the world. It makes sense that there were probably a few different attempts and not all of them worked out. They showed up and they were like, no one here knows how to make good tools. We got to go back home. Yeah, yeah.

I checked in with a paleoanthropologist who wasn't associated with this paper to kind of ask about this work from Ludovic and his team. And she said that, one, there are other pieces of evidence that have been kind of pushing the timeline of when early humans came into Europe back earlier and earlier. And also, two, that this paper was peer-reviewed by other experts in the field. So it's at least worth discussing. But she would still like to see sort of how it holds up over time to kind of see if other evidence comes out to reinforce these findings.

Whether or not the exact story of this paper is true, though, I think it tells us a lot about how hard it is to know anything about the age of Neanderthals. It seems wild to me that we are not even trying to say, like, this is how Neanderthals and early humans interacted, right? Or debating the fine points of their relationship.

We know so little that we're literally grasping at smoke to try and put them in the same place at the same time. Yeah, well, it was very striking to me that, you know, one of the first things that I asked Ludovic when I interviewed him is, can you sort of introduce us to Neanderthals? Who were they? And his immediate reaction was, we don't really know. And this is a person who has devoted their life to understanding these people.

And so I think it is, it's mostly gap. You know, we're trying to understand this creature that has been extinct for tens of thousands of years. So that is striking that we know so little, but it's also kind of amazing that we know as much as we do. I think that it's sort of, if you put me in a field with a bone,

and asked me to tell you about the person that that bone belonged to, I would be completely stymied. I would not know where to begin. But every time they've run up against a wall of knowledge of like, we've sort of, you know, we've wrung as much information out of this little bone as we can, they find some new technique that reveals a new layer of information. That was Adam Cole from Howtown.

If you want to judge the whimsicalness of Neanderthal tools for yourself, or if you want to learn more about the techniques that people use to figure out that living humans have Neanderthal DNA,

Watch Howtown on YouTube. Adam co-hosts the show with Joss Fong, who used to work with me. She's on the Vox video team. And the project of their show is just really aligned with the project of Unexplainable. They want people to understand how science works because it helps us understand how we know what we know.

In the meantime, this episode was produced by me, Bird Pinkerton. It was edited by Meredith Hodnot, who runs the show. Noam Hassenfeld is our host and does the music. Christian Ayala did the mixing and the sound design. Anouk Douceau did our fact-checking. Manding Nguyen is the fact that some toucans make a barking noise. And we're always, always grateful to Brian Resnick for co-founding the show.

A huge thanks to Ségolène Vandevelde, who took some time to explain her really fascinating work on fossil smoke. Thanks also to Hélène Rougier and to Paige Madison for their time. If you have questions about this episode or thoughts about this episode or thoughts about future episodes that we should do, please send them to us. We are at unexplainable at vox.com.

You can support this show and all of Vox's journalism by joining our membership program today. If you did that, it would be really, really appreciated. Just go to vox.com slash members to sign up. And if you can't do that for whatever reason, you can also support the show by telling a friend about the show or by leaving us a nice rating or a review. All those things really help a lot.

Unexplainable is part of the Vox Media Podcast Network. And we will be back next week.

Thank you.

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