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How Do Pheromones Really Work?

Jan 19, 2017

Part 4 of the TED Radio Hour episode The Five Senses

About Tristram Wyatt's TED Talk

Pheromones are mysterious compounds that can make a mammal smell more sexy--but that's not true for humans. Zoologist Tristram Wyatt says human pheremones are hard to find.

About Tristram Wyatt

Tristram Wyatt is a zoologist at Oxford, researching the intersection of pheromone evolution and animal behavior, particularly in mammals. He's interested in the distinction between pheromones and each individual's signature mixture of distinct molecules. Wyatt is the author of Pheromones and Animal Behavior.

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GUY RAZ, HOST:

On the show today, we're exploring ideas about the five senses, and next step? Smell.

See, so you know how some people get more mosquito bites than others?

TRISTRAM WYATT: Oh, yes.

RAZ: The reason is smell.

WYATT: Because we give off different smells.

RAZ: We give off different smells that mosquitoes are attracted to.

WYATT: There is a group in the U.K. that's been wrapping people up in silver foil, collecting the smells and seeing if the smells attract mosquitoes. And what they found is that, yes, some people are much more attractive than others.

RAZ: This, by the way, is professor Tristram Wyatt.

WYATT: I'm based in the Zoology Department at the University of Oxford.

RAZ: And professor Wyatt, he studies smells.

WYATT: Indeed, and my interest is in animals right the way across the animal kingdom through to people.

RAZ: And he says just like people smell different to different mosquitoes, lots of things smell different to different people.

WYATT: Each of us does smell a different world because when we're smelling, say, strawberries, there are hundreds of different smell molecules that have been given off by the strawberries. And what our brain is very good at is interpreting the many nerves that are stimulated by those different smells and remembering, ah, that's strawberry.

RAZ: And the amazing thing is that it's only in the last 30 years that scientists have really understood how smell works. Tristram Wyatt explains from the TED stage.

(SOUNDBITE OF TED TALK)

WYATT: 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 smiling 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 cilantro, that herb, either as something delicious or something like soap. So we each have an individual world of smell, and that complicates anything when we're studying smell.

(SOUNDBITE OF MUSIC)

RAZ: I mean, it's crazy to think that, like, some of us taste this delicious herb that I just used last night in my guacamole, and then some of us taste soap.

WYATT: Yes. It turns out that about 20 percent of people have a different version of the smell receptor, it's just a simply a matter of genetics.

RAZ: Wow.

WYATT: Now, we're familiar with colorblindness, and that's just with three receptors, the red, green and blue. Well, imagine what's going on in the nose where you have 400 receptors, and quite a few of those come in different forms that might or might not work for a particular kind of smell. Which means that the solution is don't add cilantro to all of the guacamole you're producing.

RAZ: (Laughter) Yeah.

WYATT: And an enterprising cafe in California offers two versions.

RAZ: OK, so that's how humans smell things, but what about what we smell like? You know, of course there's sweat, and the way a baby's head smells. But there's one human smell scientists have not been able to find.

WYATT: Pheromones.

RAZ: Pheromones, what most of us think of as the scent of attraction. And in just a minute, we'll hear about the scientific quest to find it. On the show today, we're exploring ideas about the five senses. I'm Guy Raz, and you're listening to the TED Radio Hour from NPR.

RAZ: It's the TED Radio Hour from NPR. I'm Guy Raz. And on the show today, ideas about how our senses shape our perceptions of the world around us. And we were just hearing from Oxford zoologist Tristram Wyatt about smell. He's been studying one aspect of smell from the animal world that we know far less about when it comes to us, pheromones. Here's Tristram on the TED stage.

(SOUNDBITE OF TED TALK)

WYATT: Pheromone - it conjures up sex abandon, loss of control. And you can see it's a very powerful word. 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 or more. Now, this is a very attractive idea. And the molecules they mention sound really science-y. (ph).

They've got lots of syllables. It's things like androstenol, androstenone, androstenedione. 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. 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. 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. Adolf Butenandt and his team 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 synthesized the molecule and then tried the synthesize molecule and the males and showed it was indeed that molecule. That's closing the circle.

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. That's the thing which has never been done with humans. Nothing systematic - no real demonstration.

RAZ: How is it that we have discovered pheromones in virtually - you know, across the animal kingdom. But we just can't figure it out in humans. What's the problem?

WYATT: I think it's we've not looked seriously. And that is strange. But, generally speaking, if you look at things like NIH funding, there is much more going towards vision and hearing. And relatively small amounts of money go towards studying smell. And pheromones would come under that area of research. The other thing is that, generally, studying pheromones in mammals is much harder. And that's because mammals, including us, are incredibly smelly. And that means if you start looking at the smells, you become overwhelmed by the number of potential molecules.

RAZ: Wow.

WYATT: So if you look in somebody's armpit, I mean, after asking them first...

RAZ: Yeah, of course.

WYATT: ...And count the different kinds of molecules, there are hundreds, if not thousands. And that complicates things because you don't know at the beginning which molecules to look at.

RAZ: So what are scientists looking for, like, exactly when they're searching for pheromones?

WYATT: So pheromones are chemical signals, something that has evolved for communication. So the way you find a pheromone is by looking for the molecules that stay the same in every male or every female, molecules that are consistent. And the rest - that's individual odors. Now, some may have more of that molecule than others. And so it's almost the success of the smelliest.

RAZ: Are we - I mean, are we getting closer to finding them, to identifying human pheromones?

WYATT: We actually do not know any sex pheromones. But at some point, we may well find them. But there is another pheromone that is actually really exciting. And it's all to do with mothers and babies. And it's some work that's coming out of France from Dijon. And they found something really neat.

(SOUNDBITE OF TED TALK)

WYATT: So this is a baby having a drink of milk from its mother's breast. But what you'll notice is a white droplet. And that's the secretion from the areola glands. Now, we all have them - men and women. And these are the little bumps around the nipple. And if you're a lactating woman, these start to secrete. It's a very interesting secretion.

So this is a sleeping baby. And under its nose, we've put a clean glass rod. The baby remains sleeping, showing no interest at all. But if we go to any mother who is secreting from the areola glands, if we take the secretion and now put it under the baby's nose, we get a very different reaction. It opens its mouth and sticks out its tongue and starts to suck.

Now, since this is from any mother, it could really be a pheromone. It's not about individual recognition. Any mother will do. Now, why is this important, apart from being simply very interesting? It's because if you're a mammal, the most dangerous time in life is the first few hours after birth. You have to get that first drink of milk. And if you don't get it, you won't survive. You'll be dead.

Since many babies actually find it difficult to take that first meal because they're not getting the right stimulus, if we could identify the molecule, synthesize it, it would then mean premature babies would be more likely to suckle, and every baby would have a better chance of survival. This is one example of where a systematic, really scientific approach can actually bring you a real understanding of pheromones.

There could be all sorts of medical interventions. There could be all sorts of things that humans are doing with pheromones that we simply don't know at the moment. So do go forward and do search for more. There's lots to find. Thank you very much.

(APPLAUSE)

RAZ: Tristram Wyatt - he's a senior researcher at Oxford, where he studies smell. You can see his entire talk at ted.com. Transcript provided by NPR, Copyright NPR.