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NOVA ScienceNOW

Neanderthals 'R' Us

  • Posted 10.10.12
  • NOVA scienceNOW

What happened to the Neanderthals? Recently, geneticists announced they’d found evidence suggesting that ancient humans interbred with Neanderthals. David Pogue delves into his genetic makeup to find out if he has any Neanderthal genes of his own.

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Transcript

What Makes Us Human.

PBS Airdate: October 10, 2012

DAVID POGUE: What sets humans apart from all the other animals?

I'm David Pogue, and on this episode of NOVA scienceNOW, I'm stepping back in time to uncover secrets of human evolution and what made us the way we are.

We're tackling some of the biggest mysteries in the history of our species, like the origin of language…

You can tell by looking at the bones if people could talk or not?

…and smashing age old myths.

I have created a tool!

Is it possible that our ability to talk lies in this ancient rock?

THIERRY CHAMINADE (Aix-Marseille University): These areas of the brain are necessary both for language and stone-tool-making.

DAVID POGUE: And language isn't the only thing that's different about humans. What about laughter? Are we the only animals that laugh?

Oh, my gosh. It doesn't sound all that laughy. It sounds a little bit more like, "I'm going to kill you now."

And is it possible that our ancient relatives, the Neanderthals live on in some of us?

ED GREEN (University of California, Santa Cruz): We have run this scan across your entire genome.

DAVID POGUE: No, no. It's not true!

In this episode, I'm finding out What Makes Us Human? Up next, on NOVA scienceNOW.

Can you imagine if more than one species of human were walking around today? I'm not talking about people who just look different, I'm talking about people who are different, like Neanderthal-different.

One of the best ways to understand what makes us truly human is to study those ancient Neanderthal cousins. And they're telling us amazing new things about a time on Earth when we weren't all alone.

It may seem shocking, but this is common in lots of animals. Just look at fish; there are 500 kinds of rays. And sharks alone have over 400 different species; 4,000 species of frogs; seven kinds of penguins.

The idea of another species of human sharing our cities isn't that farfetched. Around 30,000 years ago, there were at least four different kinds of hominids coexisting on the planet, including the Neanderthals. More than a million years ago, some of our ancestors began making their way from Africa to Europe, while the rest stayed behind. Those who remained in Africa evolved into us, modern humans. The group that went to Europe eventually developed into Neanderthals.

You know the Neanderthals, otherwise known as "cavemen." Most people think of them as being a bunch of brutes. Well, it turns out, that the more we learn about them, the closer they seem to us.

Their bones were first identified in Germany, in the Neander Valley, thus, Neanderthals. Since that discovery, about a hundred and fifty years ago, scores of Neanderthal sites have been uncovered, from the British Isles to Western Asia. We now know that Neanderthals used fire, wore clothing and made stone tools.

They thrived as skilled hunter/gatherers for at least 200,000 years. But then, thirty thousand years ago, they vanished. Why didn't they survive? And why aren't they living among us today?

Daniel Lieberman, of Harvard, looks for answers in the way human heads have evolved.

Why the head?.

DANIEL LIEBERMAN (Harvard University): Well, heads are one of the most important things about our bodies, and they're actually what makes us special, for the most part. If you were to meet a Neanderthal on, say, the subway, from the neck down you'd be basically the same. And what really makes you different from a Neanderthal is above the neck.

DAVID POGUE: It turns out our skulls and Neanderthal skulls are pretty different.

All right, so this is a mockup of a modern human?

DANIEL LIEBERMAN: Right.

DAVID POGUE: "Hi, Dan".

And this is our Neanderthal guy. If we wanted to establish the differences between the two, specifically what would you point out?

DANIEL LIEBERMAN: There are really two basic essential differences that matter. And the first is that a modern human head is much more globular. It's much more spherical, more like a soccer ball, right? It's rounded. Right? But the Neanderthal head, if you can see here, is much longer and lower. It's more like a lemon or an American football, right?

DAVID POGUE: If our skulls are the main difference between modern humans and Neanderthals, perhaps that's the key to why Neanderthals died out and we survived.

To better understand how great the difference is between our heads and theirs, I've decided to have my own noggin expanded and Neanderthalized.

Yeah, exactly…

PAUL THEREN: And in terms of your arms, you feel comfortable?

DAVID POGUE: Yeah.

Paul Theren teaches advanced film makeup at the Academy of Arts, in San Francisco.

PAUL THEREN: So make sure you get a good little glob of it there, too.

DAVID POGUE: He has agreed to take me back 40,000 years and fix me up on a date with a Neanderthal.

It's a big night, you know? It's the prom, so make me look good.

Now, suppose we wanted to make a movie about a Neanderthal guy. How would we begin to make up this guy to make him look more like a Neanderthal?

DANIEL LIEBERMAN: You want to make the face bigger, so you would add stuff to the front of the face and pull the face out as much as you could.

DAVID POGUE: My new face isn't a mask, it goes on in pieces: an enormous nose, swept-back cheekbones…

PAUL THEREN: Hold that down, hold that down. That's good.

DAVID POGUE: …really heavy brow ridges.

DANIEL LIEBERMAN: Its face is enormous. It's 20 to 30 or 40 percent larger than any modern human.

DAVID POGUE: Enlarging the back of my head takes a pound of silicone and a pint of glue.

DANIEL LIEBERMAN: You could at least approximate the shape of a Neanderthal head by adding plastic or whatever they do and give it this characteristic long shape. It's almost as if somebody took their, their fist inside the brain and just sort of punched, punched it out backwards.

DAVID POGUE: And flowing from that enormous head? Red hair. Some Neanderthals were fair skinned redheads, according to D.N.A. evidence. This would have helped their bodies generate vitamin D in the weak northern sun.

DANIEL LIEBERMAN: It's funny though, if you think about all the reconstructions you see about Neanderthals, they always give them bad hair. For some reason everybody assumes that they had no hairstyle, and I wonder about that.

DAVID POGUE: After four hours in the chair, my time travel is complete.

PAUL THEREN: I think we're, we're there.

MAKEUP ARTIST: …you still look like you're wearing…

DAVID POGUE: I am alive!

MAKEUP ARTIST: Oh, my god.

DAVID POGUE: Oh, my god.

All right, I'm ready for the streets.

If I saw this guy walking down the street, carrying a briefcase and a cell phone, would I know at a glance there was something substantially different, or would he pass for one of us?

DANIEL LIEBERMAN: I think you would probably figure out this was an extremely ugly and strange human being, but you probably wouldn't want to, like, rush and put him in a zoo. I mean you would just simply think, "Gosh, he's got a long low head and big brow ridges and a ridiculously large face and maybe a strange nose. Perhaps he needs to see a dentist." But you probably wouldn't otherwise react too strongly, I suspect.

MOUNTED POLICE OFFICER: How you guys doing?

DAVID POGUE: No doubt Neanderthals would have thought small-faced humans were the strange and ugly ones, but does the difference in our head size and shape explain why we survived and Neanderthals died out?

DANIEL LIEBERMAN: So one of the questions is, "What is it about the modern human head that might have given us some kind of advantage?" And one possibility is our brain. Our brains aren't any bigger than Neanderthals'. They might have had a different structure.

DAVID POGUE: Scientists can reconstruct the size and shape of the Neanderthal brain, by creating a cast of the inside of the skull. Where the brain pushes up against the bone, it leaves an impression of what had been there thousands of years ago.

In two areas—the temporal lobe, a center for hearing, language, and speech; and the parietal lobe, active in understanding spatial relationships—our ancestors' brains seem to be more developed than Neanderthals'.

DANIEL LIEBERMAN: So there might have been some differences in the shape of the brain that give us some clues that modern humans had cognitive abilities that were different.

DAVID POGUE: So their brains might have been bigger, but our brains might have been better.

DANIEL LIEBERMAN: That's a hypothesis. I wouldn't bet my mortgage on that yet.

The difference in our brains may have been key to our survival or it may have had nothing to do with why the Neanderthals died out. After all, lots of intellectually-challenged creatures survive without a problem.

DAVID POGUE: No can do.

But when scientists consider Neanderthals and humans, they see some possible advantages for our side: smaller heads and slimmer frames might have allowed us to outrun and outhunt our lumbering cousins; our brains and vocal cords may have been better equipped for language, meaning we could work together and plan more effectively than they could; and we may have had more babies and simply crowded them out.

All of this is speculation, but recently, scientists found a whole new window into the lives of our long-lost cousins. They successfully mapped the Neanderthal genome. And it's revealing some surprising answers, not only about them, but about us, too.

Geneticists at the Max Planck Institute, in Germany, worked for years to extract D.N.A. from the ancient bones and unlock the secrets of their genetic code.

Ed Green is one of those geneticists, and he's been analyzing the stream of letters that represent the twists and turns of the Neanderthal genome.

ED GREEN: So D.N.A. is composed of these four nucleotides. We abbreviate them A, C, G and T. Chemically, they're slightly different.

And it's the order of this A, C, G and T that encodes information, just like the order of letters in our alphabet encodes information in words.

DAVID POGUE: In human D.N.A., how these four molecules line up, over three billion times, determines who we are.

ED GREEN: It's all there. All the information is there. These four letters encode all of life.

DAVID POGUE: So what secrets are encoded in the ancient Neanderthal D.N.A.? How does it compare to our own?

Ed Green and his team lined up the Neanderthal genome with that of modern humans. Most of our sequences matched perfectly—that was expected since we share an ancient ancestor—but, time and again, something odd appeared: some people were carrying mutations characteristic of Neanderthals.

Those changes to the D.N.A. would have occurred after the Neanderthals evolved in their isolated pocket of the world. According to Ed Green, this points to one thing.

ED GREEN: They had sex; they had descendants. We find this trace in our genome today. Amazing.

DAVID POGUE: Neanderthal's genes alive in us?

Okay, the suspense is killing me. I've got to check this out to see if I, too, carry the Neanderthal gene within me.

There are several private services now offering to decode your personal genome, including whether you have any Neanderthal D.N.A. You simply spit in the tube, wrap it up and send it off. The company sends you the results in a matter of weeks.

Me? I'm going a step further.

Hey, are you Ed?

I'm getting my results from none other than Ed Green, the geneticist from the team that first mapped the Neanderthal genome. And I'm going to get to the bottom of this sensational story.

ED GREEN: I won't say get your mind out of the gutter. It's just as, it's just as dirty as you say it. There was sex between humans and Neanderthals at some point in the past, and their genes wound up, through this interbreeding event, in the genomes of some people who are alive today.

DAVID POGUE: Okay, so what did you find out about me?

ED GREEN: We have run this scan across your entire genome, but I'll show you, kind of, what we have done for one chromosome. This is chromosome 12.

DAVID POGUE: Ed Green checked the data on one of my chromosomes to see if there was any evidence of Neanderthal genes in me.

It all comes down to how those four base letters line up, on the human side or the Neanderthal side.

Ed points out to me one tiny but significant sequence.

ED GREEN: We can look at what bases occur in humans that are not of Neanderthal ancestry. You see it's the CTCT-C-G. And we know, from sequencing the Neanderthal, that they look like CTCT-T-G. And now, we can ask, do you look like the Neanderthal, or do you look like most of the humans up here? And it turns out, for this region, you have CTCT-T-G. And it's the Neanderthal.

DAVID POGUE: No, no. It's not true!

ED GREEN: Take as much time as you need.

DAVID POGUE: This changes my whole view of myself as a sophisticated, modern, sensitive man.

ED GREEN: Well, um, not only do you have a Neanderthal gene, you have many Neanderthal genes. In sum total, you are, according to the 23andMe analysis, 2.6 percent Neanderthal ancestry.

DAVID POGUE: Oh!

Do you have the Neanderthal gene?

ED GREEN: Um, I have several Neanderthal genes. I've come to grips with this though, I think.

DAVID POGUE: In fact, all humans alive on Earth, today, have them, except for most Africans, because their ancestors never met up with the Neanderthals. If you are a descendent of the modern humans who left Africa over 50,000 years ago, you have between one and four percent Neanderthal genes within you.

So we may not see Neanderthals among us, but they are still here, within us.

So, you're saying that Neanderthals today are extinct?

ED GREEN: They are extinct.

DAVID POGUE: But, but don't they, in a way, live on, because we have their D.N.A.?

ED GREEN: This is true. In that way, Neanderthals are not extinct.

DAVID POGUE: We are still coming to grips with the fact that Neanderthal genes live on in us.

While it's too early to tell what it all means, there are some indications that Neanderthal genes are present in our immune system, the part of the body that fights disease.

Some scientists believe that adding Neanderthal genes to our own may have helped us survive strange diseases, as we fanned out across the earth. Perhaps that may have had something to do with our surviving our Neanderthal cousins and going on to create civilization as we know it.

Did Neanderthals care
About their looks?
Inside Neanderthal caves,
Archeologists have found
Seashells and mineral pigment
That some say were used for…
Jewelry and make-up!
Well, maybe she's no Kim Kardashian…
But for 50,000 BC,
She's making an effort.

Credits

What Makes Us Human?

HOST
David Pogue
WRITTEN, PRODUCED AND DIRECTED BY
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Zeresenay Alemseged Profile

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NOVA scienceNOW is produced for WGBH/Boston

This material is based upon work supported by the National Science Foundation under Grant No. 0917517. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

© 2012 WGBH Educational Foundation

All rights reserved

Image

(Neanderthal and man)
© WGBH Educational Foundation

Participants

Thierry Chaminade
Aix Marseille University
Ed Green
UC Santa Cruz
Daniel Lieberman
Harvard University www.fas.harvard.edu/~skeleton/danlhome.html
Paul Theren
Academy of Arts, San Francisco

Related Links

  • What Makes Us Human?

    Find out if you’re part Neanderthal, about the evolution of laughter, what language may owe to tool-making, and more.

  • Are Neanderthals Human?

    Neanderthals present a conundrum well known in biology: What exactly is a species?

  • Neanderthals: Expert Q&A

    The leader of the team that proved we share DNA with Neanderthals answered questions about our closest relatives.

  • Decoding Neanderthals

    Shared DNA reveals a deep connection with our long-vanished human cousins.