Placeholder Image

Subtitles section Play video

  • "Pheromone" is a very powerful word.

  • It conjures up sex, abandon, loss of control,

  • and you can see, it's very important as a word.

  • But it's only 50 years old. It was invented in 1959.

  • Now, if you put that word into the web,

  • as you may have done,

  • you'll come up with millions of hits,

  • and almost all of those sites are trying to sell you

  • something to make you irresistible

  • for 10 dollars or more.

  • Now, this is a very attractive idea,

  • and the molecules they mention

  • sound really science-y.

  • They've got lots of syllables.

  • It's things like androstenol, androstenone

  • or androstadienone.

  • It gets better and better,

  • and when you combine that with white lab coats,

  • you must imagine that there is

  • fantastic science behind this.

  • But sadly, these are fraudulent claims

  • supported by dodgy science.

  • The problem is that, although there are many

  • good scientists working on what they think

  • are human pheromones,

  • and they're publishing in respectable journals,

  • at the basis of this,

  • despite very sophisticated experiments,

  • there really is no good science behind it,

  • because it's based on a problem,

  • which is nobody has systematically gone through

  • all the odors that humans produce --

  • and there are thousands of molecules that we give off.

  • We're mammals. We produce a lot of smell.

  • Nobody has gone through systematically

  • to work out which molecules really are pheromones.

  • They've just plucked a few,

  • and all these experiments are based on those,

  • but there's no good evidence at all.

  • Now, that's not to say

  • that smell is not important to people.

  • It is, and some people are real enthusiasts,

  • and one of these was Napoleon.

  • And famously, you may remember

  • that out on the campaign trail for war,

  • he wrote to his lover, Empress Josephine,

  • saying, "Don't wash. I'm coming home."

  • (Laughter)

  • So he didn't want to lose any of her richness

  • in the days before he'd get home,

  • and it is still, you'll find websites

  • that offer this as a major quirk.

  • At the same time, though,

  • we spend about as much money

  • taking the smells off us

  • as putting them back on in perfumes,

  • and perfumes are a multi-billion-dollar business.

  • So what I want to do in the rest of this talk

  • is tell you about what pheromones really are,

  • tell you why I think we would expect

  • humans to have pheromones,

  • tell you about some of the confusions in pheromones,

  • and then finally, I want to end with

  • a promising avenue which shows us

  • the way we ought to be going.

  • So the ancient Greeks knew

  • that dogs sent invisible signals between each other.

  • A female dog in heat

  • sent an invisible signal to male dogs

  • for miles around,

  • and it wasn't a sound, it was a smell.

  • You could take the smell from the female dog,

  • and the dogs would chase the cloth.

  • But the problem for everybody

  • who could see this effect

  • was that you couldn't identify the molecules.

  • You couldn't demonstrate it was chemical.

  • The reason for that, of course,

  • is that each of these animals

  • produces tiny quantities,

  • and in the case of the dog,

  • males dogs can smell it, but we can't smell it.

  • And it was only in 1959 that a German team,

  • after spending 20 years in search of these molecules,

  • discovered, identified, the first pheromone,

  • and this was the sex pheromone of a silk moth.

  • Now, this was an inspired choice by Adolf Butenandt and his team,

  • because he needed half a million moths

  • to get enough material to do the chemical analysis.

  • But he created the model

  • for how you should go about pheromone analysis.

  • He basically went through systematically,

  • showing that only the molecule in question

  • was the one that stimulated the males,

  • not all the others.

  • He analyzed it very carefully.

  • He synthesized the molecule,

  • and then tried the synthesized molecule on the males

  • and got them to respond and showed it was,

  • indeed, that molecule.

  • That's closing the circle.

  • That's the thing which has never been done with humans:

  • nothing systematic, no real demonstration.

  • With that new concept,

  • we needed a new word,

  • and that was the word "pheromone,"

  • and it's basically transferred excitement,

  • transferred between individuals,

  • and since 1959, pheromones have been found

  • right the way across the animal kingdom,

  • in male animals, in female animals.

  • It works just as well underwater

  • for goldfish and lobsters.

  • And almost every mammal you can think of

  • has had a pheromone identified,

  • and of course, an enormous number of insects.

  • So we know that pheromones exist

  • right the way across the animal kingdom.

  • What about humans?

  • Well, the first thing, of course,

  • is that we're mammals,

  • and mammals are smelly.

  • As any dog owner can tell you,

  • we smell, they smell.

  • But the real reason we might think

  • that humans have pheromones

  • is the change that occurs as we grow up.

  • The smell of a room of teenagers

  • is quite different

  • from the smell of a room of small children.

  • What's changed? And of course, it's puberty.

  • Along with the pubic hair

  • and the hair in the armpits,

  • new glands start to secrete in those places,

  • and that's what's making the change in smell.

  • If we were any other kind of mammal,

  • or any other kind of animal,

  • we would say,

  • "That must be something to do with pheromones,"

  • and we'd start looking properly.

  • But there are some problems, and this is why,

  • I think, people have not looked for

  • pheromones so effectively in humans.

  • There are, indeed, problems.

  • And the first of these

  • is perhaps surprising.

  • It's all about culture.

  • Now moths don't learn a lot

  • about what is good to smell, but humans do,

  • and up to the age of about four,

  • any smell, no matter how rancid,

  • is simply interesting.

  • And I understand that the major role of parents

  • is to stop kids putting their fingers in poo,

  • because it's always something nice to smell.

  • But gradually we learn what's not good,

  • and one of the things we learn

  • at the same time as what is not good

  • is what is good.

  • Now, the cheese behind me

  • is a British, if not an English, delicacy.

  • It's ripe blue Stilton.

  • Liking it is incomprehensible to people from other countries.

  • Every culture has its own special food

  • and national delicacy.

  • If you were to come from Iceland,

  • your national dish

  • is deep rotted shark.

  • Now, all of these things are acquired tastes,

  • but they form almost a badge of identity.

  • You're part of the in-group.

  • The second thing is the sense of smell.

  • Each of us has a unique odor world,

  • in the sense that what we smell,

  • we each smell a completely different world.

  • Now, smell was the hardest

  • of the senses to crack,

  • and the Nobel Prize awarded to

  • Richard Axel and Linda Buck

  • was only awarded in 2004

  • for their discovery of how smell works.

  • It's really hard,

  • but in essence, nerves from the brain

  • go up into the nose

  • and on these nerves exposed in the nose

  • to the outside air are receptors,

  • and odor molecules coming in on a sniff

  • interact with these receptors,

  • and if they bond, they send the nerve a signal

  • which goes back into the brain.

  • We don't just have one kind of receptor.

  • If you're a human, you have about 400

  • different kinds of receptors,

  • and the brain knows what you're smelling

  • because of the combination of receptors

  • and nerve cells that they trigger,

  • sending messages up to the brain

  • in a combinatorial fashion.

  • But it's a bit more complicated,

  • because each of those 400

  • comes in various variants,

  • and depending which variant you have,

  • you might smell coriander, or cilantro, that herb,

  • either as something delicious and savory

  • or something like soap.

  • So we each have an individual world of smell,

  • and that complicates anything

  • when we're studying smell.

  • Well, we really ought to talk about armpits,

  • and I have to say that I do have particularly good ones.

  • Now, I'm not going to share them with you,

  • but this is the place that most people

  • have looked for pheromones.

  • There is one good reason,

  • which is, the great apes have armpits

  • as their unique characteristic.

  • The other primates have scent glands

  • in other parts of the body.

  • The great apes have these armpits

  • full of secretory glands

  • producing smells all the time,

  • enormous numbers of molecules.

  • When they're secreted from the glands,

  • the molecules are odorless.

  • They have no smell at all,

  • and it's only the wonderful bacteria

  • growing on the rainforest of hair

  • that actually produces the smells

  • that we know and love.

  • And so incidentally, if you want to reduce

  • the amount of smell,

  • clear-cutting your armpits

  • is a very effective way of reducing

  • the habitat for bacteria,

  • and you'll find they remain less smelly

  • for much longer.

  • But although we've focused on armpits,

  • I think it's partly because they're the least

  • embarrassing place to go and ask people for samples.

  • There is actually another reason why we might not

  • be looking for a universal sex pheromone there,

  • and that's because 20 percent of the world's population

  • doesn't have smelly armpits like me.

  • And these are people from China, Japan,

  • Korea, and other parts of northeast Asia.

  • They simply don't secrete those odorless precursors

  • that the bacteria love to use to produce the smells

  • that in an ethnocentric way we always thought of

  • as characteristic of armpits.

  • So it doesn't apply to 20 percent of the world.

  • So what should we be doing

  • in our search for human pheromones?

  • I'm fairly convinced that we do have them.

  • We're mammals, like everybody else

  • who's a mammal, and we probably do