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  • Each of you possesses

  • the most powerful, dangerous and subversive trait

  • that natural selection has ever devised.

  • It's a piece of neural audio technology

  • for rewiring other people's minds.

  • I'm talking about your language, of course,

  • because it allows you to implant a thought from your mind

  • directly into someone else's mind,

  • and they can attempt to do the same to you,

  • without either of you having to perform surgery.

  • Instead, when you speak,

  • you're actually using a form of telemetry

  • not so different

  • from the remote control device for your television.

  • It's just that, whereas that device

  • relies on pulses of infrared light,

  • your language relies on pulses,

  • discrete pulses, of sound.

  • And just as you use the remote control device

  • to alter the internal settings of your television

  • to suit your mood,

  • you use your language

  • to alter the settings inside someone else's brain

  • to suit your interests.

  • Languages are genes talking,

  • getting things that they want.

  • And just imagine the sense of wonder in a baby

  • when it first discovers that, merely by uttering a sound,

  • it can get objects to move across a room

  • as if by magic,

  • and maybe even into its mouth.

  • Now language's subversive power

  • has been recognized throughout the ages

  • in censorship, in books you can't read,

  • phrases you can't use

  • and words you can't say.

  • In fact, the Tower of Babel story in the Bible

  • is a fable and warning

  • about the power of language.

  • According to that story, early humans developed the conceit

  • that, by using their language to work together,

  • they could build a tower

  • that would take them all the way to heaven.

  • Now God, angered at this attempt to usurp his power,

  • destroyed the tower,

  • and then to ensure

  • that it would never be rebuilt,

  • he scattered the people by giving them different languages --

  • confused them by giving them different languages.

  • And this leads to the wonderful irony

  • that our languages exist to prevent us from communicating.

  • Even today,

  • we know that there are words we cannot use,

  • phrases we cannot say,

  • because if we do so,

  • we might be accosted, jailed,

  • or even killed.

  • And all of this from a puff of air

  • emanating from our mouths.

  • Now all this fuss about a single one of our traits

  • tells us there's something worth explaining.

  • And that is how and why

  • did this remarkable trait evolve,

  • and why did it evolve

  • only in our species?

  • Now it's a little bit of a surprise

  • that to get an answer to that question,

  • we have to go to tool use

  • in the chimpanzees.

  • Now these chimpanzees are using tools,

  • and we take that as a sign of their intelligence.

  • But if they really were intelligent,

  • why would they use a stick to extract termites from the ground

  • rather than a shovel?

  • And if they really were intelligent,

  • why would they crack open nuts with a rock?

  • Why wouldn't they just go to a shop and buy a bag of nuts

  • that somebody else had already cracked open for them?

  • Why not? I mean, that's what we do.

  • Now the reason the chimpanzees don't do that

  • is that they lack what psychologists and anthropologists call

  • social learning.

  • They seem to lack the ability

  • to learn from others

  • by copying or imitating

  • or simply watching.

  • As a result,

  • they can't improve on others' ideas

  • or learn from others' mistakes --

  • benefit from others' wisdom.

  • And so they just do the same thing

  • over and over and over again.

  • In fact, we could go away for a million years and come back

  • and these chimpanzees would be doing the same thing

  • with the same sticks for the termites

  • and the same rocks to crack open the nuts.

  • Now this may sound arrogant, or even full of hubris.

  • How do we know this?

  • Because this is exactly what our ancestors, the Homo erectus, did.

  • These upright apes

  • evolved on the African savanna

  • about two million years ago,

  • and they made these splendid hand axes

  • that fit wonderfully into your hands.

  • But if we look at the fossil record,

  • we see that they made the same hand axe

  • over and over and over again

  • for one million years.

  • You can follow it through the fossil record.

  • Now if we make some guesses about how long Homo erectus lived,

  • what their generation time was,

  • that's about 40,000 generations

  • of parents to offspring, and other individuals watching,

  • in which that hand axe didn't change.

  • It's not even clear

  • that our very close genetic relatives, the Neanderthals,

  • had social learning.

  • Sure enough, their tools were more complicated

  • than those of Homo erectus,

  • but they too showed very little change

  • over the 300,000 years or so

  • that those species, the Neanderthals,

  • lived in Eurasia.

  • Okay, so what this tells us

  • is that, contrary to the old adage,

  • "monkey see, monkey do,"

  • the surprise really is

  • that all of the other animals

  • really cannot do that -- at least not very much.

  • And even this picture

  • has the suspicious taint of being rigged about it --

  • something from a Barnum & Bailey circus.

  • But by comparison,

  • we can learn.

  • We can learn by watching other people

  • and copying or imitating

  • what they can do.

  • We can then choose, from among a range of options,

  • the best one.

  • We can benefit from others' ideas.

  • We can build on their wisdom.

  • And as a result, our ideas do accumulate,

  • and our technology progresses.

  • And this cumulative cultural adaptation,

  • as anthropologists call

  • this accumulation of ideas,

  • is responsible for everything around you

  • in your bustling and teeming everyday lives.

  • I mean the world has changed out of all proportion

  • to what we would recognize

  • even 1,000 or 2,000 years ago.

  • And all of this because of cumulative cultural adaptation.

  • The chairs you're sitting in, the lights in this auditorium,

  • my microphone, the iPads and iPods that you carry around with you --

  • all are a result

  • of cumulative cultural adaptation.

  • Now to many commentators,

  • cumulative cultural adaptation, or social learning,

  • is job done, end of story.

  • Our species can make stuff,

  • therefore we prospered in a way that no other species has.

  • In fact, we can even make the "stuff of life" --

  • as I just said, all the stuff around us.

  • But in fact, it turns out

  • that some time around 200,000 years ago,

  • when our species first arose

  • and acquired social learning,

  • that this was really the beginning of our story,

  • not the end of our story.

  • Because our acquisition of social learning

  • would create a social and evolutionary dilemma,

  • the resolution of which, it's fair to say,

  • would determine not only the future course of our psychology,

  • but the future course of the entire world.

  • And most importantly for this,

  • it'll tell us why we have language.

  • And the reason that dilemma arose

  • is, it turns out, that social learning is visual theft.

  • If I can learn by watching you,

  • I can steal your best ideas,

  • and I can benefit from your efforts,

  • without having to put in the time and energy that you did

  • into developing them.

  • If I can watch which lure you use to catch a fish,

  • or I can watch how you flake your hand axe

  • to make it better,

  • or if I follow you secretly to your mushroom patch,

  • I can benefit from your knowledge and wisdom and skills,

  • and maybe even catch that fish

  • before you do.

  • Social learning really is visual theft.

  • And in any species that acquired it,

  • it would behoove you

  • to hide your best ideas,

  • lest somebody steal them from you.

  • And so some time around 200,000 years ago,

  • our species confronted this crisis.

  • And we really had only two options

  • for dealing with the conflicts

  • that visual theft would bring.

  • One of those options

  • was that we could have retreated

  • into small family groups.

  • Because then the benefits of our ideas and knowledge

  • would flow just to our relatives.

  • Had we chosen this option,

  • sometime around 200,000 years ago,

  • we would probably still be living like the Neanderthals were

  • when we first entered Europe 40,000 years ago.

  • And this is because in small groups

  • there are fewer ideas, there are fewer innovations.

  • And small groups are more prone to accidents and bad luck.

  • So if we'd chosen that path,

  • our evolutionary path would have led into the forest --

  • and been a short one indeed.

  • The other option we could choose

  • was to develop the systems of communication

  • that would allow us to share ideas

  • and to cooperate amongst others.

  • Choosing this option would mean

  • that a vastly greater fund of accumulated knowledge and wisdom

  • would become available to any one individual

  • than would ever arise from within an individual family

  • or an individual person on their own.

  • Well, we chose the second option,

  • and language is the result.

  • Language evolved to solve the crisis

  • of visual theft.

  • Language is a piece of social technology

  • for enhancing the benefits of cooperation --

  • for reaching agreements, for striking deals

  • and for coordinating our activities.

  • And you can see that, in a developing society

  • that was beginning to acquire language,

  • not having language

  • would be a like a bird without wings.

  • Just as wings open up this sphere of air

  • for birds to exploit,

  • language opened up the sphere of cooperation

  • for humans to exploit.

  • And we take this utterly for granted,

  • because we're a species that is so at home with language,

  • but you have to realize

  • that even the simplest acts of exchange that we engage in

  • are utterly dependent upon language.

  • And to see why, consider two scenarios

  • from early in our evolution.

  • Let's imagine that you are really good

  • at making arrowheads,

  • but you're hopeless at making the wooden shafts

  • with the flight feathers attached.

  • Two other people you know are very good at making the wooden shafts,

  • but they're hopeless at making the arrowheads.

  • So what you do is --

  • one of those people has not really acquired language yet.

  • And let's pretend the other one is good at language skills.

  • So what you do one day is you take a pile of arrowheads,

  • and you walk up to the one that can't speak very well,

  • and you put the arrowheads down in front of him,

  • hoping that he'll get the idea that you want to trade your arrowheads

  • for finished arrows.