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"Pheromone" is a very powerful word.
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It conjures up sex, abandon, loss of control,
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and you can see, it's very important as a word.
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But it's only 50 years old. It was invented in 1959.
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Now, if you put that word into the web,
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as you may have done,
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you'll come up with millions of hits,
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and almost all of those sites are trying to sell you
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something to make you irresistible
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for 10 dollars or more.
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Now, this is a very attractive idea,
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and the molecules they mention
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sound really science-y.
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They've got lots of syllables.
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It's things like androstenol, androstenone
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or androstadienone.
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It gets better and better,
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and when you combine that with white lab coats,
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you must imagine that there is
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fantastic science behind this.
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But sadly, these are fraudulent claims
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supported by dodgy science.
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The problem is that, although there are many
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good scientists working on what they think
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are human pheromones,
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and they're publishing in respectable journals,
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at the basis of this,
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despite very sophisticated experiments,
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there really is no good science behind it,
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because it's based on a problem,
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which is nobody has systematically gone through
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all the odors that humans produce --
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and there are thousands of
molecules that we give off.
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We're mammals. We produce a lot of smell.
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Nobody has gone through systematically
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to work out which molecules really are pheromones.
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They've just plucked a few,
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and all these experiments are based on those,
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but there's no good evidence at all.
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Now, that's not to say
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that smell is not important to people.
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It is, and some people are real enthusiasts,
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and one of these was Napoleon.
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And famously, you may remember
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that out on the campaign trail for war,
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he wrote to his lover, Empress Josephine,
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saying, "Don't wash. I'm coming home."
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(Laughter)
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So he didn't want to lose any of her richness
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in the days before he'd get home,
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and it is still, you'll find websites
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that offer this as a major quirk.
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At the same time, though,
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we spend about as much money
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taking the smells off us
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as putting them back on in perfumes,
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and perfumes are a multi-billion-dollar business.
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So what I want to do in the rest of this talk
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is tell you about what pheromones really are,
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tell you why I think we would expect
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humans to have pheromones,
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tell you about some of the
confusions in pheromones,
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and then finally, I want to end with
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a promising avenue which shows us
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the way we ought to be going.
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So the ancient Greeks knew
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that dogs sent invisible signals between each other.
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A female dog in heat
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sent an invisible signal to male dogs
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for miles around,
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and it wasn't a sound, it was a smell.
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You could take the smell from the female dog,
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and the dogs would chase the cloth.
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But the problem for everybody
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who could see this effect
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was that you couldn't identify the molecules.
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You couldn't demonstrate it was chemical.
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The reason for that, of course,
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is that each of these animals
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produces tiny quantities,
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and in the case of the dog,
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males dogs can smell it, but we can't smell it.
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And it was only in 1959 that a German team,
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after spending 20 years in
search of these molecules,
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discovered, identified, the first pheromone,
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and this was the sex pheromone of a silk moth.
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Now, this was an inspired choice
by Adolf Butenandt and his team,
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because he needed half a million moths
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to get enough material to do the chemical analysis.
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But he created the model
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for how you should go about pheromone analysis.
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He basically went through systematically,
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showing that only the molecule in question
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was the one that stimulated the males,
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not all the others.
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He analyzed it very carefully.
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He synthesized the molecule,
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and then tried the synthesized
molecule on the males
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and got them to respond and showed it was,
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indeed, that molecule.
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That's closing the circle.
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That's the thing which has
never been done with humans:
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nothing systematic, no real demonstration.
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With that new concept,
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we needed a new word,
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and that was the word "pheromone,"
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and it's basically transferred excitement,
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transferred between individuals,
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and since 1959, pheromones have been found
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right the way across the animal kingdom,
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in male animals, in female animals.
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It works just as well underwater
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for goldfish and lobsters.
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And almost every mammal you can think of
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has had a pheromone identified,
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and of course, an enormous number of insects.
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So we know that pheromones exist
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right the way across the animal kingdom.
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What about humans?
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Well, the first thing, of course,
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is that we're mammals,
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and mammals are smelly.
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As any dog owner can tell you,
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we smell, they smell.
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But the real reason we might think
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that humans have pheromones
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is the change that occurs as we grow up.
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The smell of a room of teenagers
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is quite different
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from the smell of a room of small children.
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What's changed? And of course, it's puberty.
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Along with the pubic hair
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and the hair in the armpits,
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new glands start to secrete in those places,
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and that's what's making the change in smell.
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If we were any other kind of mammal,
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or any other kind of animal,
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we would say,
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"That must be something to do with pheromones,"
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and we'd start looking properly.
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But there are some problems, and this is why,
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I think, people have not looked for
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pheromones so effectively in humans.
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There are, indeed, problems.
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And the first of these
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is perhaps surprising.
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It's all about culture.
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Now moths don't learn a lot
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about what is good to smell, but humans do,
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and up to the age of about four,
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any smell, no matter how rancid,
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is simply interesting.
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And I understand that the major role of parents
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is to stop kids putting their fingers in poo,
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because it's always something nice to smell.
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But gradually we learn what's not good,
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and one of the things we learn
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at the same time as what is not good
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is what is good.
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Now, the cheese behind me
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is a British, if not an English, delicacy.
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It's ripe blue Stilton.
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Liking it is incomprehensible to
people from other countries.
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Every culture has its own special food
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and national delicacy.
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If you were to come from Iceland,
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your national dish
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is deep rotted shark.
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Now, all of these things are acquired tastes,
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but they form almost a badge of identity.
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You're part of the in-group.
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The second thing is the sense of smell.
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Each of us has a unique odor world,
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in the sense that what we smell,
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we each smell a completely different world.
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Now, smell was the hardest
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of the senses to crack,
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and the Nobel Prize awarded to
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Richard Axel and Linda Buck
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was only awarded in 2004
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for their discovery of how smell works.
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It's really hard,
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but in essence, nerves from the brain
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go up into the nose
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and on these nerves exposed in the nose
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to the outside air are receptors,
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and odor molecules coming in on a sniff
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interact with these receptors,
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and if they bond, they send the nerve a signal
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which goes back into the brain.
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We don't just have one kind of receptor.
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If you're a human, you have about 400
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different kinds of receptors,
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and the brain knows what you're smelling
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because of the combination of receptors
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and nerve cells that they trigger,
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sending messages up to the brain
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in a combinatorial fashion.
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But it's a bit more complicated,
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because each of those 400
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comes in various variants,
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and depending which variant you have,
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you might smell coriander, or cilantro, that herb,
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either as something delicious and savory
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or something like soap.
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So we each have an individual world of smell,
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and that complicates anything
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when we're studying smell.
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Well, we really ought to talk about armpits,
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and I have to say that I do
have particularly good ones.
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Now, I'm not going to share them with you,
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but this is the place that most people
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have looked for pheromones.
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There is one good reason,
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which is, the great apes have armpits
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as their unique characteristic.
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The other primates have scent glands
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in other parts of the body.
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The great apes have these armpits
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full of secretory glands
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producing smells all the time,
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enormous numbers of molecules.
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When they're secreted from the glands,
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the molecules are odorless.
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They have no smell at all,
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and it's only the wonderful bacteria
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growing on the rainforest of hair
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that actually produces the smells
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that we know and love.
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And so incidentally, if you want to reduce
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the amount of smell,
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clear-cutting your armpits
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is a very effective way of reducing
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the habitat for bacteria,
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and you'll find they remain less smelly
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for much longer.
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But although we've focused on armpits,
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I think it's partly because they're the least
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embarrassing place to go and ask people for samples.
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There is actually another reason why we might not
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be looking for a universal sex pheromone there,
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and that's because 20 percent
of the world's population
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doesn't have smelly armpits like me.
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And these are people from China, Japan,
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Korea, and other parts of northeast Asia.
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They simply don't secrete those odorless precursors
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that the bacteria love to use to produce the smells
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that in an ethnocentric way we always thought of
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as characteristic of armpits.
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So it doesn't apply to 20 percent of the world.
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So what should we be doing
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in our search for human pheromones?
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I'm fairly convinced that we do have them.
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We're mammals, like everybody else
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who's a mammal, and we probably do have them.
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But what I think we should do
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is go right back to the beginning,
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and basically look all over the body.
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No matter how embarrassing,
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we need to search and go for the first time
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where no one else has dared tread.
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It's going to be difficult,
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it's going to be embarrassing, but we need to look.
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We also need to go back to the ideas
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that Butenandt used when he
was studying the silk moth.
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We need to go back and look systematically
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at all the molecules that are being produced,
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and work out which ones are really involved.
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It isn't good enough simply to pluck a couple
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and say, "They'll do."
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We have to actually demonstrate
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that they really have the effects we claim.
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There is one team that I'm
actually very impressed by.
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They're in France, and their previous success
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was identifying the rabbit mammary pheromone.
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They've turned their attention now
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to human babies and mothers.
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So this is a baby having a drink of milk
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from its mother's breast.
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Her nipple is completely hidden
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by the baby's head,
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but what you'll notice is a white droplet
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with an arrow pointing to it,
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and that's the secretion from the areolar glands.
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Now, we all have them, men and women,
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and these are the little bumps around the nipple,
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and if you're a lactating woman,
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these start to secrete.
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It's a very interesting secretion.
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What Benoist Schaal and his team developed
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was a simple test to investigate
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what the effect of this secretion might be,
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in effect, a simple bioassay.
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So this is a sleeping baby,
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and under its nose, we've put a clean glass rod.
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The baby remains sleeping,
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showing no interest at all.
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But if we go to any mother
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who is secreting from the areolar glands,
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so it's not about recognition,
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it can be from any mother,
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if we take the secretion
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and now put it under the baby's nose,
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we get a very different reaction.
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It's a connoisseur's reaction of delight,
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and it opens its mouth
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and sticks out its tongue
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and starts to suck.
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Now, since this is from any mother,
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it could really be a pheromone.
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It's not about individual recognition.
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Any mother will do.
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Now, why is this important,
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apart from being simply very interesting?
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It's because women vary
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in the number of areolar glands that they have,
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and there is a correlation between the ease
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with which babies start to suckle
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and the number of areolar glands she has.
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It appears that the more secretions she's got,
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the more likely the baby is to suckle quickly.
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If you're a mammal,
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the most dangerous time in life
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is the first few hours after birth.
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You have to get that first drink of milk,
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and if you don't get it, you won't survive.
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You'll be dead.
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Since many babies actually find it difficult
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to take that first meal,
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because they're not getting the right stimulus,
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if we could identify what that molecule was,
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and the French team are being very cautious,
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but if we could identify the molecule,
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synthesize it, it would then mean
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premature babies would be more likely to suckle,
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and every baby would have a better chance
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of survival.
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So what I want to argue is this is one example
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of where a systematic, really scientific approach
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can actually bring you a real understanding
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of pheromones.
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There could be all sorts of medical interventions.
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There could be all sorts of things
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that humans are doing with pheromones
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that we simply don't know at the moment.
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What we need to remember is pheromones
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are not just about sex.
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They're about all sorts of things to do
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with a mammal's life.
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So do go forward and do search for more.
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There's lots to find.
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Thank you very much.
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(Applause)
