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Stone Age Language Mystery

  • Posted 10.10.12
  • NOVA scienceNOW

Using modern-day flint-knappers as their subjects, anthropologists are studying what happens in the brain when people make stone tools. Their results suggest that the evolution of human language and stone tool use may have gone hand in hand.

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Launch Video Running Time: 13:08

Transcript

What Makes Us Human.

PBS Airdate: October 10, 2012

DAVID POGUE: There's one thing that shows up on all of the lists of what makes us human: language. Our ability to share our thoughts and complex information with others far surpasses all the barks, squeaks and growls of our animal friends.

So where did it come from? Believe it or not, the origin of language is one of the biggest mysteries in human evolution, but could an amazing new solution be found in this suitcase?

Inside, anthropologist David Frayer, of the University of Kansas, has samples of the kind of evidence scientists depend on to trace the history of language.

Oh, man, this is the briefcase you carry around?

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

DAVID FRAYER (University of Kansas): Well, with various levels of success, yes.

DAVID POGUE: Frayer brought me all kinds of stuff, from a Neanderthal skull and brain casts to a tiny bone found in our throat that helps us speak. But our language investigation soon centers on the oldest skull in Frayer's case.

DAVID FRAYER: We can take a leap back to this specimen, back to around 1.8 million years ago. When it was found, it was considered to be really revolutionary, because it showed this really large brain.

DAVID POGUE: The brain of this Homo erectus is much smaller than our modern brains, but twice the size of a chimpanzee brain. So this ancient ancestor might have had the capacity for language.

DAVID FRAYER: It suggests that language was possible in the individual.

DAVID POGUE: So, that's a little mind blowing—or skull blowing, I should say—that 1.8 million years ago, we might have had speech.

DAVID FRAYER: Now, whether they were stringing together the grammar and the syntax that we associate with modern language or modern writing, that's anyone's guess.

DAVID POGUE: The remains of early humans are extremely rare, and, of course all the soft tissue —noses, ears, tongues—that may be clues to speech are long gone, but Frayer does have one more item that may be a key clue to the origins of language.

It's not a skull, it's not even a bone. It's a rock?

DAVID FRAYER: It's more than a rock, it's a symmetrical tool.

DAVID POGUE: But I thought we were talking about language.

DAVID FRAYER: You go with what you got, sometimes, you know? When you're at 2,000,000 years ago, you don't have a lot of complete fossils. But what this tells us is that mindset of…the individual that made this had a brain that was thinking about a shape, when they were making the tool, as opposed to just whacking away at a rock.

DAVID POGUE: It turns out, when scientists are looking at the mysterious business of where language began, stone tools provide some of their best clues, because they offer a tiny glimpse into the workings of an ancient mind.

Something called the "Oldowan chopper," which looks like a charcoal briquet, is considered the first tool, two and a half million years old. But scientists get really jazzed when it comes to another tool, the "Acheulean handaxe," the very tool David Frayer is waving in front of my face.

DAVID FRAYER: This kind of tool involves a different kind of thought process. Chimpanzees make tools like this. If I held these two tools up and I said, "Which kind of tool would you think was made by a human-like ancestor as opposed to something else?" I think you would say the symmetrical one.

DAVID POGUE: For sure.

The Acheulean handaxe was born when Homo erectus got a bright idea for stone tool 2.0: a new product that was flat, sharp on the edges and could be used to perform a variety of essential tasks.

One and a half million years ago, it was the smartphone of its day.

Dietrich Stout at Emory University is investigating the possibility that making the Acheulean handaxe actually helped prepare the brain for language.

DIETRICH "DIETZ" STOUT (Emory University): The hypothesis is that learning to make more complicated stone tools caused evolutionary changes in the brain that paved the way for the evolution of language.

DAVID POGUE: Now that's an intriguing hypothesis: a million years of, years of making a gazillion stone tools may have established pathways in the brain humans could use for something else: language.

But how could you prove such an idea?

Stout turned to Bruce Bradley, experimental archeologist and stone-toolmaker extraordinaire, to try to understand the mental skills required to craft these ancient objects.

Bradley has trained himself to make stone tools using the same materials early humans would have used.

And now, he's agreed to give me a short lesson in tool-making…

BRUCE BRADLEY (University of Exeter): It's more finesse than it is strength.

DAVID POGUE: …so that I can step back in time and enter the mind of my ancient ancestors.

If a common Homo erectus can do it, I'm sure I can too.

BRUCE BRADLEY: Now, this is the piece that you're going to hit.

DAVID POGUE: Okay.

BRUCE BRADLEY: And this is the hammer stone that you're going to use. Just give that a try.

DAVID POGUE: All right.

BRUCE BRADLEY: It's finesse, not power.

Sort of a glancing blow: rather than into it, you want to glance it.

DAVID POGUE: All right.

BRUCE BRADLEY: Not too hard. You don't need to hit it that hard.

DAVID POGUE: Not so hard? Okay.

BRUCE BRADLEY: Uh, you're turning…you need your elbow up. That'll help your wrist, and not, not inward, outward.

DAVID POGUE: Okay.

BRUCE BRADLEY: There you go. Look at that.

DAVID POGUE: Wow.

I have created a tool! Civilization has changed forever, Og!

BRUCE BRADLEY: Yes, I'm sure.

Try again.

DAVID POGUE: My moment of triumph is brief. Getting from flake to handaxe proves far more complicated than I imagined.

BRUCE BRADLEY: And remember, glancing blow, elbow up.

DAVID POGUE: Maybe you should just do it.

BRUCE BRADLEY: No, no, no.

DAVID POGUE: Okay.

When rock star Bruce Bradley's making a tool, he's thinking several steps ahead, using more brain than brawn, a key point for Dietrich Stout.

DIETZ STOUT: There's a structure to the actions. There are certain rules. In order to do this, you have to do that, but all the time they are related to the goal. And it's the same thing in language.

DAVID POGUE: Just as words in their proper places form sentences, each individual strike must be done in the proper order to get the desired result: a flat stone blade.

BRUCE BRADLEY: So what we're looking at is complex, sequential, abstract thought. Because what is language? It's complex sequential thought, okay?

DAVID POGUE: I see. So in order to have language, you first have to have the same sorts of mental skills that, that we're seeing.

BRUCE BRADLEY: That's what we're trying to figure out.

DAVID POGUE: But for the tool-to-language hypothesis to work, there would have to be similarities between what the brain is doing while making a handaxe, and how it behaves while forming a sentence.

That's something Dr. Cynthia Thompson, at Northwestern University, knows a lot about.

CYNTHIA THOMPSON (Northwestern University): The focus of my research is to look at what parts of our brain are actually activated when we compute very difficult sentences.

DAVID POGUE: Thompson works with people who have trouble speaking because their brains have been damaged by stroke or other injuries.

Kristen Carlstedt, is one of her research subjects.

Following a stroke, four years ago, Kristen became one of a million Americans with a condition called "aphasia".

CYNTHIA THOMPSON: Kristen has classic agrammatic aphasia.

So, she can understand single words, she can produce single words.

ELLYN (Therapist): Okay, what's this?

KRISTEN CARLSTEDT (Research Subject): Um, pitcher…

CINDY THOMPSON: But people with agrammatic aphasia have problems with complex sentence processing.

ELLYN: The cat is chased by the dog.

What would you say for this one?

KRISTEN CARLSTEDT: The dog, no, the cat is…hmm.

DAVID POGUE: Thompson searches for answers in the images of brains of Kristen and other patients like her.

In M.R.I. brain scans, dark areas mean damaged tissue. Thompson found that agrammatic aphasia patients do share a striking characteristic, damage to the left hemisphere of the brain, home to a mysterious region known as Broca's area.

One of the many parts of the brain associated with language, Broca's area's seems especially important when it comes to grammar.

CINDY THOMPSON: Broca's area is, is crucial to sentence processing. When we have patients who have stroke, and they have damage that encroaches on Broca's area, that's when we start to see problems with sentences.

DAVID POGUE: Okay, fine, but does Broca's area have anything to do with stone-tool-making.

DIETZ STOUT: What we want to know is do, in fact, particular kinds of stone-tool-making, that we see coming along at particular times in human evolution, draw on or recruit Broca's area.

DAVID POGUE: Stout, himself, recruited a French neurologist, Thierry Chaminade, to set up an experiment that could answer that question.

Since it's impossible to have people actually make stone tools while having their brains scanned, Chaminade set up the next best thing: a special projector that could beam images of stone-tool-making into the M.R.I. machine.

Studies have shown that watching an activity excites the same areas of the brain as actually performing the activity.

THIERRY CHAMINADE: The same brain area responds when you observe someone else doing the action. So perceiving and performing an action activates the same regions.

DAVID POGUE: So, in order to see what areas of the brain are activated by making stone tools, Chaminade projected images onto a screen, in the M.R.I., and had subjects watch videos of Bruce Bradley at work.

In one video, the subjects were observing the creation of a simple tool, the Oldowan chopper. In another, they were observing a complex tool, the Acheulean handaxe.

The results were, pardon the pun, striking. Watching the video of simple choppers resulted in mild activity in Broca's area, but observing the complex Acheulean handaxe caused four times more activity.

So, the same area of the brain we use in forming complex sentences is also hard at work when we make complex tools.

THIERRY CHAMINADE: These areas of the brain are necessary both for language and stone-tool-making. These two things co-evolved.

DAVID FRAYER: It's probably the most interesting breakthrough about the origin of language, which pushes it way back to just a little less than 2,000,000 years ago, totally fascinating studies.

DAVID POGUE: Today, there are over 7,000 languages spoken throughout the world. They may sound different, but in every case, they're drawing on the same regions of the brain.

If you had told me that stone-tool-making had something to do with our ability to speak, I would have said you've got rocks in your head, but these studies indicate that once Homo erectus got creative with stone, our brains were on the way to inventing the most powerful tool of all: language.

Look at that. Look at that. Let the crowds roar! That is a masterpiece, don't you think?

BRUCE BRADLEY: It's delightful.

How early in life do babies
Start to learn language?
Could it be…in the womb?
Studies of newborn babies
Found that their cries mimic
The speech patterns of their mothers.
French newborns cry
More with a rising pitch
German cries have
A falling pitch
So when you hear this…
Remember, there could be
A lot more going on
Than a wet diaper.

Credits

What Makes Us Human?

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WRITTEN, PRODUCED AND DIRECTED BY
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NOVA scienceNOW is a trademark of the WGBH Educational Foundation

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

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Image

(tool)
© WGBH Educational Foundation

Participants

Bruce Bradley
The University of Exeter huss.exeter.ac.uk/archaeology/staff/bradley.shtml
Thierry Chaminade
Aix Marseille University
David Frayer
University of Kansas
Dietrich Stout
Emory University
Cynthia Thompson
Northwestern University

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.

  • Stone Age Toolkit

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  • Mapping the Brain

    Use some of the same imaging techniques neuroscientists use—from MRIs to PET scans—to see inside the human brain.

  • Decoding Neanderthals

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