Sealed with a Bacterial Kiss

And that's a good question. What is it? Right? We're gonna get get to that. Is it something we learn? Is it something that we do instinctively? And if we do it instinctively, why are we doing it? What possible service uh could could could there be in placing your lips on another creature's lips and then moving those lips around and then what happens back terially? What's the profile

going on there? Um? And before we dive into some of that and even some of the history of the kiss, I wanted to mention that Ship Walter, who was writing for Scientific American, has a great sort of like lips unfold. The kiss from this starry eyed perspective, says quote. When passion takes a grip, a kiss locks two humans together in an exchange of sense, tastes, textures, secrets, and emotions. We kiss furitivelylstiviously, gently, shyly, hungrily, and exuberantly. We kiss

in broad daylight and in the dead of night. We give ceremonial kisses, affectionate kisses, Hollywood air kisses, kisses of death, and at least in fairy tales, pecks that revived princesses. Nice, I mean, and indeed, there are a lot of different kisses,

so there's there's no there's no single kiss. There's the In fact, if you go by the work of seventeenth century German poet, literally historian and translator Martin von kim be Uh, he wrote a thousand page encyclopedia of kissing that recognized twenty different varieties, including two notable ones that kiss bestowed by superiors on inferiors, which we don't really get around here at the House of Works, thankfully, and uh and also hypocritical kiss. But you mentioned the kiss

of the kiss of death because of doom. I mean, that's a big one too, and instantly brings my mind to the Godfather. And of course, uh, you know the story of Judas and Christ betraying him with a kiss. But the kiss goes back far, far deeper in history than that it does. The first documentation of kissing is in the four Vedic sanscript texts written in India around and it describes the act. And then you have an

Indian epic poem, Maha Barata, which mentions kissing. And this actual this poem was passed down orally for centuries and then it was finally written down in threeft C. Yeah, we've actually talked about the Mahabarada before. Tells the story of the great rivalry between the Curus and the Pandavas starting in the middle of the first millennium um b c. And you have gods and kings and also the wonderful stuff.

There's a there's a great uh play and film adaptation of the play out there that the English language that I definitely recommend people check out. Yeah, it's a very rich narrative. Now, another very rich narrative that features kissing is the Kama Sutra, which was written in the sixth century.

Now you throw in a little bit of Alexander the Great invading India, and you have, you know, public kissing becoming a thing, and it begins to spread, say to the Roman Empire, and it sort of comes out of the bedroom or the homes of people and out onto the streets. Though not entirely so, I mean, this is this is very much a Western thing. Yeah. The stats tend to say that it's practiced by at least nine of cultures among sexual and romantic partners, and that tim

person is interesting. We started looking back at their the accounts of Charles Darwin in his book The Expression of the Emotions in Man and Animals. He uh, he talked about the rubbing of noses as an alternative to the kiss, practiced for instance among the Inuits, where we get the idea of the Eskimo kiss the rubbing of the noses. Um. And you see also across Africa, the Pacific and in the America's um plenty of the examples of people that

didn't really do the kiss until Europeans introduced it to them. Yeah, although especially with with the nezzling of noses, that is an intimate act, it's just not as much of a bacterial exchange. And I'm even thinking about Hawaiian culture in which, um, there's this bowing of the heads next to each other and you exchange a breath, so you come very close to each other. The idea is that you're you're you're

meeting each other and taking in a breath. And uh, when some of the European explorers showed up, they wouldn't do this with the Hawaiian people, and they became known as how he's h A O l e. The no breathers, that they wouldn't get that close to each other in exchange. This moment, I was reading that during the ravages of the Black Death fourteenth century Europe, that you saw kissing falling out of fashion because obviously there's a lot of Black Death going along around, so you kind of cut

back on some of your your interpersonal physical touching. But uh, while kissing fell away, licking, sniffing and nibbling of the eyebrows comes into play as an alternative, which, again to your point, kind of fills the same void, the close intimate physical contact that that makes up for the locking of lips. Right, So, even though there may not be that specific expression of kissing, there are other expressions like the nuzzling of eyebrows. Yeah, yeah, wow, I feel about that.

It sounds kind of hard to do. I mean, especially depending on the how big the nose is. Like, if you have like flatter nose, I feel like the otherwise you just have to you have to navigate around a lot of nose in some cases. All I'm saying, yeah, my kid and husband are in for a treat tonight. I'm gonna see how the nuzzling of eyebrows goes. Um. Well,

here's the deal with kissing. Though. It is such an important feature of the way that we communicate that there is actually a field of study of it called philomatology, and those people who are committed to studying kissing have brought us a bunch of information about its effects on the brain and the body, because if you think about it, it is really a full body event when you have

a good smooch going on. It's true. Yeah, I mean, just start breaking it down on a physical level, and just not a physical level without getting into you know, the nervous system and hormones and what have you. Um, I think just in terms, for instance, of the of the muscles, right, you have the orbicularious oris, and this runs around the outside of your mouth. Yeah, this is if you push your lips together, it's kind of hard to talk like that, kind of like a pucker those

that's the bricky lorius. Okay, so that's the big one. That's I mean that we're gonna discuss. There are a lot of additional muscles, but that's one of the main ones that you're flexing when you go in for a smooch, because then you have several other muscles around the lips that are moving. You have the zygomaticus major the zygomaticus minor,

you want to use them both of course. Also what we're talking about thirty four different muscles here involved in the smooch, Yeah, and about a hundred and twelve postural muscles. So we think of your neck, back, and your chest muscles all being engaged in a full on assault kiss. Yeah. Some of the X ray images we're looking at when we're putting together this podcast, and indeed the image that should be the the cover image for this episode on the landing page for this episode of Stuff to Blow

Your Mind. Uh, you get this sense of this muscular face, this communication array that we use to communicate and interact with the world. Then it's all. It's all involved in this kiss, just on a muscular level, it is, and it's exquisitely sensitive stuff going on here, because if you think about it, it it all begins with the thinnest layer

of skin on our body. And of course I'm talking about lips, which are among the most densely populated with sensory neurons of any body region and as a result, or about one hundred to two hundred times more sensitive than the fingertips. To think of that, that just that initial meeting of the lips is causing a lot of data to be uploaded to your brain and carried there, which is creating this cascading effect in your body. Yeah, a lot of its subconscious as we'll get too into

as well. They do have nerves. They fire off five of our twelve cranial nerves. Uh, So you have all this this information firing through the nervous system, sensory information going to the brain for processing. Yeah, and that's right.

So it's shuttling on all sorts of messages um about temperature, tastes, smell and movements of this entire smooch going on in the summato sensory cortex, which extends from one side of the brain to the other, and it has a large portion that's devoted to picking up signals from the lips, the tongue, nose, and cheek areas, and then it maps that and in that map, the lips loom really large.

It's kind of like a neon sign here when you're kissing, because the size of each of those represented body parts or regions is proportional to the density of its nerve endings. So again, as I mentioned, the flips have a ton of nerve endings. When they're engaged on that map, it's just saying, hey, this is huge, this is important. Yeah.

It brings me back to the homunculous images that a lot of people probably seen, Like not the actual medieval alchemical homuncular little dude, Yeah, not the little dude that you're growing in a vat. I love that, but the representation of the human body as it would appear if size was determined by nerve endings. So it's just like a little squat little dude with these enormous lips. Oh I like that. Yeah. Um, So all of this is going on, and as a result, you have neurotransmitters and

hormones being released, like dopamine. As we know, it's a neurotransmitter associated with feelings of deshire and reward, and it spikes in response to novel experiences, which is interesting because that sort of explains why a kiss with someone new can feel so special. Yeah, there's a little bit of the butterflies and the nerves going on, but also this is new data that you're taking and that's really making the dopamine thing. Your brain is saying, my tongue has

never been inside this mouth before. There's all sorts of new information the process. And kissing also stimulates adrenaline, which helps our bodies to anticipate what might occur next. And yeah, I mean it's all part of that. That's that stereotypical passionate kiss. You know, if you're watching the film and you see two people just sort of having this very stale moment together locking lips, you're not buying it, you know, they're not They're not releasing adrenaline, that's not getting them

ramped up. Yeah. It reminds me also of Gustav Climpse the kiss, which is that all enfolding and encompassing kiss. That's you know, in the representation of two people kissing, just this ornate display of colors and what looks like sensations in that painting. Yeah, I mean they the two individuals in a really bassionate kiss should look like they are trying to eat each other with their mouths. Yeah.

It should become like a auaborous thing. Yeah yeah, um, alright, so we also have heart rates increasing and oxygen flowing more freely through the blood vessels pupils dilating. Its interesting. Yeah, this one I read is this supports the Yeah, this one I read that might be the reason a lot of people close their eyes during a kiss, because otherwise you're just staring into like really big, wide, crazy eyes the whole time, and that can be awkward. Yeah. All right,

we're gonna take a quick break. When we get back, we're going to talk about the bacterial exchange of a good old French kiss. All right, we're back, and this is where things are going to get a lot more interesting because a lot of what we've covered for sort of the basic mechanics of the kiss, and so a lot of you are probably thinking, well, of course, a lot of muscles are engaged of course, Uh, dopamine, serotonin, adrenaline, what have you. Is released that seems to happen in

any kind of human experience that we've discussed. It's worth discussing, right Yeah, Like we we see a piece of chocolate cake, same thing happens, right Yeah. But when you start looking at the bacterial level here, when you start looking at the kiss as a convergence of microbiomes, that's where things start really getting trippy and taking us a lot, a lot further from the realm of passionate Valentine's Day kisses

and Hollywood, uh hero saves the Day kisses. Yeah, this is where we're going to take that kiss and just make it the anti Valentine's kiss right now. And we'll do that by discussing it is in it because you've got that saliva, and you've got mucus membranes, and that's in about nine milli milli leaders of water and about point seven milligrams of that protein, point one eight milligrams of organic compounds delicious, and point seven one milligrams of

different fats. And then you have a little bit of sodium chloride at point four or five milligrams and maybe even up to seven different types of bacteria. And although it's it's you know, somewhat rare, it's possible to transmit mononucleosis herpie simplex one in gastric ulcers. So those are a couple of examples of germs that can be swapped

and lurking in your kisses mouth. It's basically two train cars arriving at the station at the same time, and they both unload, and it's just people crossing each other to get onto each each train, which is you basically just describe the study about the French kiss? Uh would was? I love that there's even a study about a French kiss and I love that. Um. They were cruited twenty one couples in this study and had them snug for

science essentially. Yeah, and this covered people between the ages of seventeen and forty five, so it's not just a matter of finding a bunch of young kids and getting them to smooch. It's so it's a little more varied than that. Um. And before they locked lips, the participants were asked to swab out to measure the amount and the kinds of bacteria presence. You're getting a good idea what the current population is inside of mouth A and

mouth B and C and D yeah, baseline. Yeah. And then at this point they asked one member of each kissing couple to eat some probiotic yogurt now. And the reason here is because this contains strains of Lactobacillus and bifeto bacteria serve as markers to look for in the kissy. Yeah, that's right, because they know that. The researchers know that normally saliva way contain about point one of Lacto basilius

and biphobacteria. But after these these couples kissed and they exchanged their content, it was found out that the bacteria in the non yogurt drinking partner rose to point by four and this led the researchers to estimate that each intimate liplocked and tonguelocked kiss that can last ten seconds or more will transfer about eighty million bacteria into your

partner's mouth. Okay, so people are probably wondering at this point is that a good thing or a bad thing, because it might sound if you, especially if you're a little more on the germophobic side of things and maybe a little adverse to kissing strangers. On the bus already. This might sound like just an unnecessary invasion of your

mouth space. It does. It sounds a little terrible, like why would we do this in the first place, But the fact of the matter is is that the higher the diversity of your microbi I am in your mouth, well, the better it is for you. Okay, So the more kisses, the better, The more passionate the better. I mean, I wouldn't know, if someone has, you know, an outbreak around their mouth, I wouldn't go kissing on them, or if someone is sneezing or you know, I wouldn't pursue you know,

certain circumstances kissing. But yeah, in general, mean, what doesn't kill us makes us stronger, right, Okay. So if yeah, so the opportunity for a kiss comes about and it's like you would have taken it anyway, definitely go in and happy kiss because there's a potential health benefit there possibly,

But don't hold us to that. All right, We're gonna do another break and when we come back, we're going to get into the nitty gritty or we're going to get into the reasoning behind the kiss and and again, because it's going to get into it even Traz your territory. All right, we are back. Why do we kiss? Propert Lamb? Well, there are a few possibilities, right Um. One of the big ones out there, and we touched on a little bit already, is that it's just something we started doing

and that we learned. And you can point to those ten percent of humans that don't kiss and say, well, it's it's evidently not really a human thing across the board. So is it really in a human behavior or is it just something we saw on TV? Now I had to think about this one a bit and imagine most of you can can relate to this, like think back to your your first kiss, or even just the first time you wanted to kiss somebody, like why did you

want to kiss them? Like? What was it? Just because you saw it on a million movies and TV shows prior to that, and you saw it on every advertisement because especially here in the U S, it's it's everywhere in Western culture, it's the kisses everywhere? So am I just picking up on all those signals and thinking That's what I'm supposed to do, that is what is expected

of me. I feel like at first it's a familiar thing, right, Like I look at that with my daughter who's just started kissing or friends at age four, no matter what, because it was her expression of love. And now she's six and she's just had her first kiss from a boy or however she's casting it. And she also has watched a lot of different things that are depicting kisses

among opposite gendered people. I mean, I mean, she's not watching soap operas or anything, but she's watching Ninjago, and you know, two of the characters have a little peck on the cheek or something. Um, So, in that respect, I see it as cultural. However, it's not that easy just to say that's the answer, right, So if we get into the idea that it is instinctive, they're they're roughly three different hypotheses for why do we kiss to arouse? Obviously sort of the ramping up to the actual uh

genetic genetic act of breeding with another person. Um, it's also the possibility that it's all about just cementing the relationship. And again it has to do with with with with mate bonding or essentially testing out of a potential mate kind of a genetic test. And this is where things get really fascinating. Yeah, and I did want to mention too before we kind of dive into those topics when

when we talk about it being learned. Um, there is a British zoologist and author, Desmond Morris, who in the nineteen sixties first proposed that kissing could have evolved from the practice in which primate mothers chewed food for their young and then fed the mouth to mouth, so preasticating food. And I feel like we talked about this, Yeah, we've talked about I feel like we've talked about that in

terms of passing on beneficial bacteria to the young as well. Again, mouth to mouth contact comes down to bacteria and the microbiome and and very minute data passed between mother and child, between two mates, etcetera. So evolutionary biology might say something along the lines of, so if chimps do it, so two could have our hamt id, and so might we.

And in fact, they're are a plenty of other cultures today that will actually do that to cheat their food for their baby and instead of using the grinder or something, cheat some food for my son before, I mean, not not super recently, but it's been done. I mean because he's like sixteen now, right, but you know, you find yourself in those situations where it's like, all right, I could get out a knife and and cut this in half for him, or I can just bite the thing

in half and give him part of it. Why not? Sure? And I mean right, it's a convenient thing. And then you put the nursing equation with us, which it really gets sort of interesting here because then the child may be learning to associate lip pressure with a loving act. Now, consider that two thirds of all people turn their head to the right when kissing. And this is according to psychologists on your constrick of your university in Germany. And

now stay with me. Why does that matter? Because this behavior may mirror the head turning preference observed in babies when their breastbed. Huh huh it is. It's a hum moment, right, It's something to consider, just the whole right handed thing.

Like I'm trying to think back on and every kiss I've ever had if I turned to the right, and I guess that means that the other person turned to the right too, right, because yeah, I know, againe it agether another test from my husband and my daughter running tonight. So anyway, just a couple of things to think about But there are other reasons that we do this. Indeed, and this is where it comes back to that old song. It's in his kiss, right, like if he loves you

or something, it's in his kiss. That's good. Yeah, that's the one. So in a way, I'm not sure about love. Love is a whole different kettle of fish. But the idea of just pure genetic mate selection, just the straight up genetic mission that that that governs our lives. Human a needs to find a human being so that they can procreate and and do what their their their genes are telling them to do. The idea here is that a kiss serves as an act of chemical profiling that

human will. A sticks its tongue into human bees mouth and uh and and basically conducts a core sample of what that that person consists of, particularly their immune system and uh and then crunches that data to see if this is the type of person that they want to

bread with. It's a real possibility, especially when you consider that A two thousand and nine study of one thousand college students by Gordon Gallup Jr. A professor of psychology at the University of Albany, showed that of men and sixty percent of women reported that after feeling attracted to someone initially, the attraction ended after the first kiss, so that just that one kiss put the kai bosh on. Hey, I don't think we should really go any further here.

As reading that, Cheryl Christian Baum, author of the Science of Kissing, found that women are attracted to men who have a different genetic code from their own immune system, which is of course the hallmark of sexual reproduction. You want to have two different sets of genes so you can produce variety in the offspring, right, better, better, stronger offspring,

and have a better potential for survival. Um. And this this kind of meshes with some of the stats to show that that women tend to be more into the kiss than the men. Well, it is interesting to see that slight uptick that men and sixty six percent. You could say, to a certain smaller degree, women are a little bit more discriminating when it comes to trying to

ferret out whether or not that person it's compatible with them. Um. Gordon g. Gallup says that kissing is quote a complicated exchange of information or factory information, tactile information, and postural types of adjustments that may tap into underlying evolved in unconscious mechanisms that enable people to make determinations about the degree to which they are genetically incompatible. So to your

point earlier, some of this is just subconscious information being processed. Yeah, because when you're engaged in that passionate kiss, uh, you're not thinking about all this. You're not thinking, all right, is this the one is just said, I wonder what their jeans are like, I wonder if if we can we can produce a child that's going to survive the next big plague or what have you. But under the surface, there's a lot, potentially a lot of computation going on. Yeah.

And when you look at literature on kissing, a lot of people will site the old sweaty armpits study of women sniffing the the t shirts of men that have, you know, their sweat on it. And the conclusion to that was that they were attracted to men who had different um sent profiles from themselves that indicated that the men's immune systems were different from them. So that again, the greater the diversity here, the better for any sort

of coupling and perhaps producing of a child later on. Yeah, and I do want to come back as well to again that the fact that a passionate kiss especially is not just a matter of the lips. It's a it's potentially a full body kind of experience. You're you're engaging in all of your senses, So it's a it's like a full sensory read out of an individual. But but

at the at the shallow end of the intimacy pool. Yeah, there was actually just reminds me of the writer Flannery O'Connor, and there was a fellow writer who tried to pursue a kiss with her, and he said that it was so devoid of passion and really any sort of um connection that he called it a memento mori. That's what she was communicating to him is, you know, there's absolutely nothing that's going to go on here, momenta morian is in terms of the the artistic tradition of having these

images that they reminds you that death is imminent. Death is the ultimate um destination in life. Right, It's like kissing the grim Reaper a little. Yeah, I think there were no sparks there between the two. Now, the big question becomes, of course humans do it? Do other species kiss? Well?

Basically No, I mean because when you when you start looking at the human kiss, and in all its varied forms, and especially the passionate human kiss, there's nothing really like apples to apples like it elsewhere in the animal k Yeah, some of its interpretation too, right. So you see great apes press their lips together to express excitement, affection, or reconciliation. That's a big deal too, right, like saying, Okay, it's

we're good here, right, we're all cooperating. Maybe this happens after um, there's been some sort of fight or agitation.

And according to Chip Walter, writing for Scientific American, binobo's, which are genetically similar to us, although of course um we are not their direct descendants, are particularly passionate bunch again the interpretation here and in in that article for Scientific American, Walter says that Fronds B. M. Duwal, who is Emery professor, recounts a zookeeper who accepted what he thought would be a friendly kiss from one of the

banobo's until he felt the apes tongue in his mouth. Now, if you look to other animals, you'll find other examples of sensory apparati engaging with each other. Snails caressing antenna's birds touching beaks. There's a lot of snout licking going on.

I mean, really, if you base your research just solely on YouTube clips, look, then it seems like every animal kisses, especially animals that are pets, animals that we've anthropomorphized to varying degrees, right, Yeah, and elephants too with their trunks entangled, right, And they've been observed doing this before too, and trying to calm each other down, and um, what seems like

calming each other down? I mean if you break down a kiss into the into terms of one partner, particularly that a female getting some sensory information on a potential mate, then you see the various exams. I mean, even a giraffe sampling urine is essentially the same sort of communication that's going on with a kiss. Yeah. And as Walter had indicated in the quote that I read at the beginning,

a kiss can be so many different things. It can be sexually motivated, or it could be a cooperative kiss, right, or as you had mentioned too, there's like the kiss of death. So the motivations are just as varied as anything else in the human experience or in the animal experience. Now, there's some additional benefits to kissing. Um. We already touched on potential microbiome related benefits, but just on a regular, relieving, daily stress level of activity, it seems like a good

passionate kiss here and there will definitely set you right. Yeah, it will reduce your stress hormone cortisol, thereby lowering blood pressure and optimizing your immune response. That's the thought at least. And it could even help fight cavities, right Like, if if you swapped spit with someone else via a kiss, then you may adopt a bacterial strain that can really fight against plaque that you lack. You you lack this bacterial strain. In fact, there's this idea that you could

even one day have bacterial mouth transplants. I mean, you call them kisses, but I mean you could actively seek someone who has a great bacterial profile in their mouth and say, I would like some of your saliva. Yeah. And also it's just worth noting that kissing, the very active kissing, also produces more saliva in your mouth, and more saliva is good if you want your natural defenses against plaque to take action. Indeed, Um, so that's kind of you know, an overall. I mean, and it's just

great too. Write kissing is a pretty awesome thing. I like it. Um, it can also apparently ease pain. There's there's some evidence for this is a little a little if you be aware of anyone who says they'll take your pain away with a kiss. But you do have blood vessel dilation going on, so arguably there can be some minor level of pain relief going on, or at least distraction. That's what I was thinking. At the very least,

it's distracting in a good way if it's welcomed, of course. Um, and let's let's talk about welcomed and I'm welcomed kisses too, because I've read this a little bit. If you engage in kissing with your pets, you might want to think twice. Dogs can carry worms, fun guy, And they can carry pathogenetic pastorella in their mouths. And cats. Don't even get started on cats. It's like a far worse thing. Well, if you own either of these animals, and I own a cat, like, you see what they do, You see

where they you see what they're up to. All right, So there you have it. Um, Hey, if you want more on this topic, other topics we've covered in the past. Go to stuff to Blow your Mind dot com. That's where you'll find all of our past episodes or videos or blog posts. Links out to our social media accounts, information on how to contact us, pictures of what we look like, pretty much everything. It's the mothership. Oh, and also go to how stuff works dot com. Check out

how Kissing Works by tray C. V. Wilson. Yeah, this article goes into the history, goes into the you know, the muscles, the nerves, a lot of the information we've discussed here, and you can just you can get it all illustrated out there for you, uh, in the ten pages or so. Yeah. Also real quick, um, if you're interested in finding out more about that study, it's a two thousand and fourteen study. It's called Shaping the Oral

Microbiota through Intimate Kissing. That's the French kissing. One eighty million bacteria is strong. All right, you have thoughts, well, we would like to put our eyes on them. Please send them our way, and you can do that by sending an email to below the mind at how stuff works dot com for more on this and thousands of other topics. Does it How stuff Works dot Com, difficult to get youth group, difficult to eat Parlia