Celebrating 50 Years of Pheromone Research In 1959, two scientists coined the word "pheromone" to describe the chemicals used for communication between members of the same species. Tristram Wyatt, author of an essay in Nature detailing the history of pheromone science, highlights research milestones.
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Celebrating 50 Years of Pheromone Research

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Celebrating 50 Years of Pheromone Research

Celebrating 50 Years of Pheromone Research

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You're listening to Science Friday on NPR. I'm Ira Flatow. We're going to go switch gears and talk about an anniversary. Yes, 50 years ago, two scientists thought up the term "pheromone." They used the new word to describe a chemical messenger released by the female silkworm moth, a silkworm moth, to attract males. It was the first pheromone chemically identified in the scientific literature. But since then, scientists have catalogued these chemical messengers for bees and lobsters and the elephants and ants and even the lowly bacteria.

Of course, if you Google pheromones, a bunch of hopeful ads pop up. You get premium human pheromones, 100-percent money-back guarantee. You'll also get pheromone cologne, sex pheromones, the only proven brands seen on TV guaranteed to attract sex now. But despite all the hype for human love potion based on pheromones, scientists still have not been able to conclusively identify these elusive compounds in humans, though my next guest says we may be finally on the right track. He has an essay this week in the journal Nature, highlighting the history of pheromone research. Tristram Wyatt is the author of "Pheromones and Animal Behavior: Communication by Smell and Taste." He is also a senior researcher in the Department of Zoology at the University of Oxford in England. Welcome to Science Friday, Dr. Wyatt.

Dr. TRISTRAM WYATT (Senior Research Associate, Department of Zoology, University of Oxford): Thanks for making me welcome. Good evening.

FLATOW: Good evening to you. Give us the day - go back in history to those - the first pheromones. Did researchers know what they had then?

Dr. WYATT: Well, chemical communication wasn't new in 1959. There're been lots of stories. But it really was, as you said, the very first time in 1959 that the chemistry had been tracked down, and it was an amazing task, given the techniques they had at that time available. So, it would've taken something like half a million silk moths to get enough material for Butenandt, the Nobel Prize-winner, to actually identify Bombykol, that first sex pheromone.

FLATOW: And - but this is a concept that goes way back to the ancient Greeks, does it not?

Dr. WYATT: Indeed, the ancient Greeks knew that a female dog in heat was enormously attractive to male dogs, and they knew it was some kind of secretion, although they obviously couldn't put their finger on it.

FLATOW: And how many pheromones - fast-forward today - how many different animals have we recognized pheromones working in?

Dr. WYATT: Well, probably many, many thousands of pheromones have actually been identified so far as the chemistry is concerned, but we're particularly good at working on moths. And that's partly because with the very good agricultural system of universities in the U.S. and the importance of crops over the years, there's been lots of money going into studying those pheromones because of the potential use as a sort of green pest control. But apart from that, we also know the chemical identity of pheromones in everything, as you mentioned, from lobsters to salamanders, possibly some birds. Almost any animal you mention is likely to use a pheromone, and that turns out to be the rule rather than the exception, even if we haven't identified it yet.

FLATOW: Right.

Dr. WYATT: And ironically, one of the only ones we don't know still is that female dog pheromone, even though every dog owner...

(Soundbite of laughter)

Dr. WYATT: Knows that it's incredibly powerful.

FLATOW: By - then we must also assume by extension that there are human pheromones that we haven't identified yet.

Dr. WYATT: Very much so. They've - I think humans, well, as in all the areas of science, humans are hard to work on, and part of it is the complexity of our behavior. But it's also because the main probable place that pheromones come from is our armpits. The reason for saying that is not just because they're gross...

(Soundbite of laughter)

Dr. WYATT: But because they gain their special smells when we reach puberty. They're slightly more smelly in the male than the female. And everything points, just in the same way as in other animals, that these ought to be the sources of pheromones. The problem is that wonderful bouquet, an acquired taste, that wonderful bouquet is very complex. So, there are thousands of different molecules in that mixture, and tracking down which ones are the pheromones is a much harder task even than working on moths.

FLATOW: Wow. Wasn't there a study a couple of years ago of putting sweat on - above the lips of women...

Dr. WYATT: Yep.

FLATOW: To sniff in and they were - their hormones kicked in when they smelled this?

Dr. WYATT: Yeah. There's some very nice studies. So, what we're looking at is very good evidence...


Dr. WYATT: For one kind of pheromone, which we call primer pheromones. So, it doesn't have an instantaneous effect like the dog pheromone, bringing in the dogs, the male dogs, from miles away. This is a much more subtle thing that lasts over a longer period and acts not on behavior directly, but acts on the hormones. One of the studies you're mentioning is Martha McClintock, now at the University of Chicago, and she originally had done some very nice work on menstrual synchrony, the way that women's periods start to synchronize if they're living in a close proximity like in a dorm. And in 1998, she continued that work and showed it, just as you've mentioned, that an extract from the underarm of one woman could affect the menstrual cycle of another if it was put on the upper lip of the woman receiving. So, it's something that you can sniff. And the nice thing about her study was it was all done double blind and there were also some good solvent controls, so we know it's not the alcohol or whatever it is that the sweat was dissolved in.

Despite that good physiological evidence - and this other nice evidence from George Preti at the Monell Institute in Philadelphia, looking, in that case, male secretions and the effect on female hormone release - despite all that good evidence, it is elusive. We know that it's in the solution somewhere, but nobody to date has identified what the molecules are that are having this effect. When they do, we'll be able to say we've got the first human pheromone. Until then, we have good indications that these primer pheromones - no molecule identified. But sadly, all those things that you find in Google - and it's just the same in the UK - sadly, they could increase your confidence through a placebo effect. But sadly, there's no evidence that they actually work to make people irresistible. I wish they did.

FLATOW: Yeah, me, too. 1-800-989-8255 is our number, 1-800-989-TALK, talking with Tristram Wyatt about pheromones on Science Friday. So, it's a question - is it a question that there are too many things in there to isolate and you'd have to try each one of them? Or then - or might be a combination of things or what?

Dr. WYATT: Well, it's a bit of both, and that is actually one of the problems. If you take an extract, especially from a mammal, that has all these compounds in, you run it to a gas chromatograph, as you probably know, and that separates out each of the molecules into a single peak, if you're lucky. And the problem with a mammal secretion is with all that bacterial fermentation happening in the underarm - which is actually, really, how the smell works; it relies on bacteria to create the smell - given that incredibly complex odor, you've got perhaps 1,000 molecules to look through, and the biologically interesting ones won't necessarily be the biggest peaks. So, that's the first one. You can't just go for the high mountains. You have to look in the valleys as well. And as you said, it may not just be one compound acting by itself; it may be a combination. And that's something they found in moths very early on, and we know in mice that some of their pheromones are two compounds working together, and only if the two are presented together do you get the effect. So, it is a very complex situation.

FLATOW: Hmm. It's even more complex when you think that if it's been shown that human armpit sweat is a trigger - we don't know what's in there...

(Laughing) It's something that's so repulsive to people to begin with is actually the attractant.

Dr. WYATT: Well, you could have too much of a good thing.

(Soundbite of laughter)

Dr. WYATT: In the ancient Greek, actually, one poet was giving some advice to a friend of his, and he was saying, so long as your armpits start, or rather, keep smelling like goats, you're never going to find a partner. So, although we might think that it's a relatively recent thing to find armpits a bit much, it does go back awhile. It is also rather difficult study in modern society because we do have an aversion now to any human odor, and that is culturally driven; it's perfectly possible to find it attractive. And there's a wonderful and, I think, true story about Napoleon, writing back to Empress Josephine from the Russian campaign. And he's telling her apocryphally - actually, you can see the letter on the Internet - don't wash; I'm coming home soon. And this is two weeks before he's going to get home. So, he was actually a real enthusiast.

FLATOW: Hmm. Maybe it's true. Maybe the ancient Europeans, I mean, a few hundred years ago, who didn't take a bath for a month...

Dr. WYATT: Yes.

FLATOW: Maybe they knew something we didn't know.

Dr. WYATT: Indeed.

(Soundbite of laughter)

Dr. WYATT: I think we also habituate. If you're around it all the time, then you stop smelling it.

FLATOW: I have a question, 1-800-989-8255, from James in Caledonia, Michigan. Hi, James.

JAMES (Caller): Hi, there.

FLATOW: Hi, there. Go ahead.

JAMES: Great show. Hi. My question is whether - what is it that compels my wife to try to smell my t-shirts or my sweatshirt, my sweaters? And I'd happily take the answer offline.

FLATOW: Yeah. We will, too.

(Soundbite of laughter)

FLATOW: What is there about that? Is that a pheromone, or is that something else?

Dr. WYATT: Well, I think it just means he's irresistible.

(Soundbite of laughter)

Dr. WYATT: That's - well, there's all sorts of things going on there. Part of it is things that may not actually be pheromones but may be what we call signature odors each of us have partly through genetics, partly through the bacteria and partly through what we eat. So, it's a really complex mixture of odors that each of us produces that's very characteristic. One of the nice things that has been done is that if you ask people to actually put it to the test, don't use a picture, but actually use smell, they're very good at identifying their partner, their children, their babies, and the babies also recognize their mothers and fathers. So, smell is very important even if we don't normally think about it. One thing we do know is that the smell of a partner is actually very comforting, and we choose partners possibly because they smell really nice to us. So, it's actually no surprise that if the two of you are very well suited, that she enjoys sniffing your smell. It probably means a lot to her.

FLATOW: Hmm. Are all the pheromones, are they used for some sort of mating purpose? I mean, I know - that we've had E. O. Wilson on talking about leaving - ants leave trail scents and things like that.

Dr. WYATT: Yeah. Well, E. O. Wilson was one of the pioneers, and in fact, very early on, in 1963, he had a fantastic Scientific American article on just this topic called "Pheromones." His early work, and he was one of the first people to do it, was working on fire ant pheromones in the trails. And you're right; basically, almost every aspect of social insect life is driven by pheromones. So, you've got those trail pheromones; you've also got alarm pheromones, which he also worked on, so that if one ant is attacked, they release the alarm pheromone, and ants from all over rush over and attack the predator. They also have sex pheromones just the same as other animals for the queen and king, as it were, to meet on a nuptial flight.

FLATOW: Mm-hmm.

Dr. WYATT: But all sorts of aspects of the social life of the social insects is driven by pheromones.

FLATOW: Interesting.

Dr. WYATT: Including their nest building.

FLATOW: Interesting. Talking with Tristram Wyatt on Science Friday from NPR News. Could there not also be human ones, when we talk about, I can smell the fear in him, you know? Those kinds of pheromones?

Dr. WYATT: There is suggestive work from various groups, one in Texas and one on Long Island, looking at just that. We're at that kind of stage where we have suggestions of pheromones. We have a bio-essay(ph); we have a test that we could use to identify what molecules are. But we're at a very early stage. And someone's made a nice analogy. If you think back to the heart drug, digitalis, well, a long time back, a couple of hundred years back, we were using the actual foxglove flower. So, your physician would actually be prescribing so many flowers taken from the foxglove.

FLATOW: Mm-hmm.

Dr. WYATT: Eventually, the active ingredient, the active molecule, was identified, synthesized, and now your physician can give you a precise dose. There was always a risk before, actually, because, depending on the season, the flowers would either be very strong or not strong. So, every time you took the drug from the flower, original thing like a tea, you were putting yourself at risk. So, where we are with pheromones with these things about fear and other ideas is the suggestive behavioral work, some magnetic resonance imaging of the brain showing some kind of effect. There's been some physiological work, too, but that's only the beginning of actually working out if there really is a molecule and then a stage further identifying what those molecules might be.

FLATOW: Mm-hmm. Let's see if we can get a phone call in from Bailey in Michigan State University. Hi, Bailey.

BAILEY (Caller): Hi. How are you today?

FLATOW: Hi, there. Quickly, please.

BAILEY: I have heard anecdotal evidence of male iguanas attacking women who are on their menstrual cycle in a way that would be similar to how they would attack a female for mating. Is there any evidence of pheromones affecting trans-species?

Dr. WYATT: Well, there are, and the most fantastic example is, perhaps, the bolus spider in the Southern states of the U.S. And the spider quite illegally synthesizes moth pheromones that are so exact that they attract male moths of that species, and when the moth gets close, the spider throws out its bolus - it's basically like a spider's web in a little gob of goo like a bolus - and it catches the moths and brings it in. But you're right; there are other species interactions, because if you're sending out a signal, then basically anybody else can overhear it. Now, those anecdotes, if you could actually quantify those and substantiate them, might give you a way of looking for what the human pheromone was. If this turn out to be a widespread occurrence, then that would give you a clue. If you could find out what the lizard pheromone was, that would give you a way into the human one. So, that's, actually, quite an intriguing idea.

FLATOW: All right. Well, we're going to have to leave that for the next episode of Know Your Pheromones.

(Soundbite of laughter)

FLATOW: Dr. Wyatt, thank you for taking time to be with us. It's fascinating, absolutely fascinating stuff, and thank you for being - staying up late in Great Britain for us today.

Dr. WYATT: Thank you. My pleasure.

FLATOW: You're welcome. Tristram Wyatt is the author of "Pheromones and Animal Behavior: Communication by Smell and Taste." He's also a senior researcher in the Department of Zoology in the University of Oxford in England. That's about all the time we have for today.

(Soundbite of music)

FLATOW: Greg Smith composed our theme music, and we had help from NPR Librarian Kee Malesky. If you have comments or questions, you can write to us the classic way, with pen and paper, Science Friday, 4 West 43rd Street, Room 306, New York, New York, 10036. Also, surf over to our Web site, sciencefriday.com, where we're Twittering and podcasting and blogging and doing all kinds of digital stuff and looking for your suggestions. Science Friday's pick of the week, our new video, is up this week by Flora Lichtman, and it's about writing with light. It's very, very, very interesting. Have a great look at it. Also have a great weekend. We'll see you next week. I'm Ira Flatow in New York.

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