A Brief History of Making Out

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Speaker 4 When Shayna Roth was in 10th grade, she set her mind to something.

Speaker 5 I was like very determined to get kissed soon.

Speaker 6 This was in Michigan in the mid-2000s, but the thing driving Shayna's determination was 1980s teen movies.

Speaker 5 I wanted that like John Hughes,

Speaker 5 you know, nerdy girl gets good kind of a romance. Maybe I saw 16 Candles too often.

Speaker 16 16 Candles was written and directed by John Hughes and it ends with Molly Ringwald's character Samantha sitting cross-legged in front of her birthday cake across from her crush, the dreamy Jake Ryan.

Speaker 19 Happy birthday, Samartha.

Speaker 16 As the music swells,

Speaker 15 they lean towards one another.

Speaker 19 It already came true.

Speaker 12 The candles illuminating them from beneath, and they kiss for the very first time. I could believe

Speaker 21 you.

Speaker 5 And I just was constantly thinking of how to make something

Speaker 5 worthy of a scene in a movie in my life.

Speaker 11 So, when Ben, a smart boy in her class with a lot of floppy brown hair, asked her out, it was game on.

Speaker 5 This guy's gonna kiss me. He doesn't know it yet, but this is gonna happen for me.

Speaker 27 For the date, Ben's dad dropped them off at the mall to see Miracle, a movie about the unexpected triumph of the 1980 U.S.

Speaker 28 men's Olympic hockey team.

Speaker 29 What do you play for? USA!

Speaker 5 Let's go a little bit more. I don't know why we saw this movie.
Like, I don't care about hockey.

Speaker 24 During the movie, Shanna spent a lot of time thinking about exactly what she wanted to happen after.

Speaker 5 I had a line that I was like, I'm going to use this line, and this is how I'm going to get kissed. And it's going to be perfect.
So, credits are rolling. It's playing that

Speaker 30 sing with them, sing von and it.

Speaker 30 Sing with them, sing for the year. Sing for the love, sing for the the tears.

Speaker 5 Aerosmith, there you go.

Speaker 5 Theater empties out and we're just kind of sitting there just going, okay, what do we do now? And I look at him and I go, so are you going to kiss me on this date or do I have to do everything myself?

Speaker 28 That was the line she had planned.

Speaker 5 I mean, I must say, I executed it perfectly. And so he kind of like looked at me, obviously stunned, and we kissed.

Speaker 5 And we even kissed again when he dropped me off and walked me to the door.

Speaker 15 Shana had done it.

Speaker 32 She had successfully arranged this monumental rite of passage, this step towards adulthood.

Speaker 6 She and Ben would even date for a couple of months and make out sometimes.

Speaker 26 For Shana, who's now a senior producer at Slate, it was the beginning of a life full of kissing.

Speaker 5 I can't imagine like going through life, like especially like as a teenager and just like not kissing.

Speaker 38 What if I told you that like in all the cultures all around the world, in like half of them,

Speaker 27 people don't kiss like you did?

Speaker 29 Wait, what?

Speaker 14 This is Dakota Ring.

Speaker 28 I'm Willa Paskin.

Speaker 16 Kissing, romantic, sexual, steamy smooching is so ingrained in our desires, habits, and culture, it seems like a fact of life.

Speaker 26 Like breathing or eating, we just do it.

Speaker 40 But what if it's not like that at all?

Speaker 33 In this episode, we're going to look at passionate kissing dispassionately.

Speaker 3 Not as something instinctual and innate, but as a cultural practice with a history of its own.

Speaker 3 We're going to follow the kiss backwards in time, trying to find its origins and turning up surprises along the way.

Speaker 16 So today on decodering, with the help of apes, Neanderthals, herpes, and Bronze Age pornography.

Speaker 35 How long have we been kissing?

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Speaker 3 I want to start by defining the different kinds of kisses. And I don't mean good kisses or bad kisses, sloppy kisses or tongue kisses.

Speaker 10 I mean scientific kisses.

Speaker 43 There are actually many categories of kisses.

Speaker 16 Sabrina Imbler is a science writer at Defector.

Speaker 43 I mostly write about creatures, but humans are creatures as well.

Speaker 24 And there is one kind of kissing we human creatures do more than any other.

Speaker 43 There's like the friendly kiss, which happens between friends, oftentimes between parents and children or other family members.

Speaker 12 This is one of a number of affiliative kisses. Kisses that are about forming and creating social bonds, not doing anything erotic.

Speaker 37 And this friendly kiss, which doesn't even have to be lip to lip, is something that humans everywhere do.

Speaker 43 Platonic kissing, like that happens between a parent and a child, is universal. It's found in every human culture.

Speaker 42 Humans everywhere, in other words, smooch on their babies.

Speaker 14 But there's other kinds of affiliative kissing too.

Speaker 43 There's also like, they call it a submissive kiss, which sounds very kinky, but it's just kind of like in historical societies where like people would kiss the feet of like a ruler, that would be like a submissive kiss.

Speaker 6 And we still do a version of this, like when subjects kiss the hand of the queen or Catholics kiss the pope's ring.

Speaker 14 There's also kisses that are used as a greeting, like how French people often kiss each other on both cheeks.

Speaker 6 This kind of kiss isn't sexual either.

Speaker 45 But of course, there is a kind of kiss that is.

Speaker 43 So there's the romantic sexual kiss, which basically just means like kiss that accompanies romantic or sexual interest or both.

Speaker 40 It's thought that this kind of mouth-to-mouth kiss evolved out of affiliative kissing.

Speaker 26 Basically, because our mouths are so sensitive, some people started to use them in a more erotic way.

Speaker 6 And the romantic sexual kiss was born. A kiss that Sabrina has more succinctly termed the sexy kiss.

Speaker 43 I feel like sexy kiss really encompasses everything.

Speaker 26 And it's this type of kiss that is such a big deal in our culture. I just want your extra time and your

Speaker 26 kiss.

Speaker 46 It's such a dominant script, what researchers call sexual script for us that kissing is part of courtship.

Speaker 26 Dr.

Speaker 3 Justin Garcia is the executive director of the Kinsey Institute at the University of Indiana.

Speaker 46 Especially in the current modern moment. I mean, you can't put on a movie about romance that there's not kissing involved, right?

Speaker 47 I believe in long, slow, deep, soft, wet kisses that last three days.

Speaker 6 That's Kevin Costner talking about getting to first base in the baseball romantic comedy Bull Durham.

Speaker 29 Come on.

Speaker 24 Over the years, kissing has come up often in Justin's work.

Speaker 12 And as he looked at it more closely, he learned learned there were lots of theories about why we do it, like to increase intimacy and arousal, and to get conscious and unconscious hormonal and biological cues about the health of our potential mates.

Speaker 9 But he also realized there was an assumption underlying all of these theories.

Speaker 46 We take for granted that everyone must do it, that it must be adaptive, it must have evolved. So really the question was, well, actually, is that first assumption true? Is everyone really doing this?

Speaker 32 He thought we probably were, that all humans sexy kiss, but he wanted to do a proper academic study to nail it down.

Speaker 48 So Justin emailed me and he said, I think this is a universal. Why don't we just document it?

Speaker 2 Dr.

Speaker 24 William Jankobiak is a professor of anthropology at the University of Nevada, Las Vegas.

Speaker 26 He's done a number of cross-cultural studies where you look at a wide array of research to try and suss out a pattern.

Speaker 11 And that's exactly what Justin wanted him to do in order to determine whether or not romantic sexual kissing actually is universal.

Speaker 48 And I thought, yeah, makes sense to me.

Speaker 26 So they started pouring over the ethnographic literature.

Speaker 16 Studies anthropologists have written about hundreds of cultures, some in the past, some in the present, looking for mentions of romantic sexual kissing and expecting to find them all over the place.

Speaker 13 And they did in one particular kind of society.

Speaker 48 In complex state civilizations, societies, kissing is universal.

Speaker 3 A complex state civilization is one with laws and hierarchies and trade and agriculture that can support millions of people.

Speaker 32 So it's one like our own.

Speaker 26 These kinds of societies are not new.

Speaker 32 Rome, Egypt, Babylon, Japan, Imperial China were also complex civilizations, and they had kissing too.

Speaker 26 Most people in the world today live in a society like this, which is to say, they live in a society with romantic sexual kissing, even if it's only practiced in private spaces.

Speaker 6 This is why it feels like this kind of kissing is everywhere.

Speaker 9 But complex civilizations are not the only way humans can arrange themselves.

Speaker 39 And as Justin and Bill began looking into smaller societies, romantic sexual kissing got harder to find.

Speaker 48 As I started reading through the ethnographers, I wasn't getting any of the data. Particularly when you're looking at old research, it could be an oversight.

Speaker 48 In other words, it was there, but no one ever commented on it. You'd be hard pressed looking at the entire thousand articles and books on China for someone to mention they use chopsticks.

Speaker 48 It's so ubiquitous, you don't write on it because everybody knows they use chopsticks. So perhaps kissing was that as well.

Speaker 6 So they started reaching out to anthropologists who are experts in what used to be called called hunter-gatherers and are now called foragers, basically migratory societies, about 15 to 40 people.

Speaker 48 I asked them, did you see any kissing? And everyone said no. And now that really became very enlightening.
And I thought, my goodness, we're really documenting the opposite of our opening hypothesis.

Speaker 14 They next reached out to ethnographers of slightly larger societies, living in groups of about 100 to 200 people.

Speaker 6 And now they started to see more of a split.

Speaker 39 Some of these cultures had romantic sexual kissing, but others didn't.

Speaker 7 It wasn't that sex and romance and love were unknown in these societies.

Speaker 25 It's just that mouth kissing wasn't a component of them.

Speaker 28 Though an ethnographer studying a group living in the Amazon did notice something else.

Speaker 48 A lot of it was kind of graphic and nibbling on each other's eyebrows, but there was no kissing. So they were sucking on eyebrows, but not lips.

Speaker 26 Dr.

Speaker 32 Garcia really got the goods when he came across an opinion expressed by a woman in one of the groups that doesn't kiss.

Speaker 46 I remember reading this one piece from an Aboriginal woman in Australia and made a comment of like asking, if you like someone, why would you spit in their mouth?

Speaker 50 All told, they looked at 168 distinct cultures from all over the world, the Arctic to the tropics and in between, and they found that just 46%

Speaker 51 engaged in romantic sexual kissing.

Speaker 40 Less than a half.

Speaker 29 That was a surprise to us.

Speaker 46 We thought the number was going to be a lot higher.

Speaker 48 I thought it was a universal. And then no, it's not.

Speaker 46 There was an assumption, this sort of classic ethnocentrism, that we think what we see in our societies is true of societies all around the world. And we found no.
The answer is no.

Speaker 33 Their findings suggest that romantic sexual kissing is not genetically hardwired.

Speaker 24 Otherwise, everyone would do it.

Speaker 44 It's nurture, not nature.

Speaker 3 But for people who do sexy kiss, there are benefits.

Speaker 46 When you put a face close to another face, you get all, you can see someone, you smell them, you feel them, you taste them, you get a lot of sensory information.

Speaker 25 Some of that sensory information may even register subconsciously.

Speaker 2 When we kiss someone, we're getting their pheromones and information about their health.

Speaker 10 And that data might help us determine whether we want to keep kissing them.

Speaker 3 But even if kissing is useful and pleasurable, Dr.

Speaker 12 Garcia thinks.

Speaker 46 Probably in the sense of where it emerged from, that we've been doing it forever is probably just not true.

Speaker 29 So if we haven't been sexy kissing forever, just how long have we been doing it?

Speaker 6 When we come back, we're gonna talk to a couple who came up with an answer to this question while talking about it over dinner.

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Speaker 53 Even if you are trying to avoid watching the video of Charlie Kirk's shooting, social media makes it really hard.

Speaker 54 And it's not like it's some crazy niche thing where you have to go and find a snuff film somewhere. It's actually on the biggest social media platforms in the world, which is kind of crazy.

Speaker 53 Now that platforms have essentially ditched content moderation, is this our future?

Speaker 54 There's probably never been a time in human history where you had so much extremely graphic, violent imagery that not only was available to you at the drop of a hat, but also that in some cases, whether you you wanted it or not, might end up showing up in front of you.

Speaker 53 I'm Lizzie O'Leary. Listen to my conversation with Craig Silverman, one of the smartest journalists thinking about the internet, on Friday's What Next TV D, wherever you get your podcasts.

Speaker 6 Sophie Lund Rasmussen is a Danish biologist and zoologist.

Speaker 55 I'm actually an expert on the research on European hedgehogs.

Speaker 16 The noises you're hearing are hedgehogs huffing and snuffling.

Speaker 55 I've always loved hedgehogs.

Speaker 38 She's married to trolls punk Arbel.

Speaker 56 I'm an assistant professor in asterology at the University of Copenhagen.

Speaker 51 A seriologist study cuneiform, one of the earliest scripts in world history.

Speaker 6 It originated around 3200 BCE in modern-day Iraq and Syria, a few hundred years before the pyramids in Egypt.

Speaker 34 So a little more than 5,000 years ago.

Speaker 57 If you see a cuneiform tablet, can you just like read it?

Speaker 56 It depends a bit on the genre. Some genres you can sort of read.
Then there are some unique cases where it's much more difficult and requires years of looking at the same lump of clay.

Speaker 26 It's an obscure field to most of us.

Speaker 27 But when Sophie and Trolls met for the first time at a bar and he tried to explain what he did, Sophie lit up.

Speaker 55 People don't know what he's doing, right? And I was like, oh, so you study asseriology.

Speaker 44 How did Sophie, a hedgehog expert, know so much about a seriology?

Speaker 56 Sophie was originally a Near Eastern archaeologist.

Speaker 55 So I was the first person who ever knew what he was actually doing.

Speaker 16 Sophie and Joel have now been married for 12 years.

Speaker 27 And during that time, they never thought much about kissing.

Speaker 39 Except, you know.

Speaker 30 Do you guys like kissing?

Speaker 55 Yes, we do.

Speaker 55 Like everybody else.

Speaker 55 I just took it for granted that that was a completely natural behavior,

Speaker 55 that everybody practiced kissing. And of course, kissing was a very old practice.

Speaker 2 But then one night at home, over dinner, it came up.

Speaker 55 We are a very nerdy couple, right? And

Speaker 55 so it was just, you know, down to, so did you notice that paper that came out the other day? This was really interesting.

Speaker 18 That paper was about herpes.

Speaker 25 Herpes, more officially, the herpes simplex virus, or HSV-1, can create cold sores on your mouth.

Speaker 8 And it's so common today that about 3.7 billion people carry it.

Speaker 31 That's half the global population.

Speaker 34 And the paper, which was published in the academic journal Science in July of 2022, laid out research about when HSV-1 had started to conquer the world.

Speaker 3 To do that, it sequenced four herpes genomes taken from the teeth of ancient European skeletons.

Speaker 11 It found that there had been a real shift in HSV-1 dominance in Europe around 5,000 years ago during the Bronze Age.

Speaker 2 It also included a hypothesis about why that shift might have happened.

Speaker 56 That shift might have occurred because there had been a migration and people had perhaps introduced sexual romantic kissing into Europe.

Speaker 56 And that could then have led to the spread of this herpes simplex virus 1 and sort of accelerated it.

Speaker 33 Herpes is spread by among other things, kissing and sex to this day.

Speaker 30 So it seemed possible these same acts had helped spread it in the past.

Speaker 26 But sitting at dinner, Sophie and Trolls realized they were both a little surprised by the idea that romantic sexual kissing was ever new.

Speaker 32 Why was the paper hypothesizing that it had only arrived in Europe some thousands of years ago?

Speaker 26 What was the evidence for that?

Speaker 56 So we read the article and

Speaker 56 sort of stumbled upon in their supplementary materials that the reference they cited as the earliest evidence for this romantic sexual kiss was allegedly from India.

Speaker 39 This has been the academic consensus for years that the first documented appearance of romantic sexual kissing is in written Sanskrit texts from around 1500 BCE, about 3,500 years ago.

Speaker 9 No one thinks this was the first kiss, but it is considered the first documented one.

Speaker 3 And so the hypothesis was herpes could have spread from South Asia as migration occurred.

Speaker 26 But when Trolls saw this theory, his asseriologist sense went off.

Speaker 55 And Trolls went, I honestly think I can beat that with a thousand years.

Speaker 55 And then we had to go to the office and look, you know, after dinner

Speaker 55 to double check.

Speaker 6 That night, instead of dessert, they read ancient cuneiform references to romantic sexual kissing, some of which go back 4,500 years.

Speaker 26 That's 1,000 years older than the Sanskrit texts mentioned in the Herpes paper.

Speaker 16 Most early cuneiform texts are administrative, but important slices of ancient life appear in them, even personal stuff.

Speaker 56 And you then get, for example, this bizarre lawsuit-like legal text that has to do with a woman swearing to refrain having sexual relations to another man that she had sexual relations to before, but they're not married.

Speaker 56 And there, you know, kissing is also mentioned in relation to this intimacy.

Speaker 16 There's also a stone slab that shows a couple locked in an embrace.

Speaker 35 The woman's leg is lifted over the man's hip, and they're clearly having sex, and also clearly kissing.

Speaker 56 And we also have some what you could call erotic literature

Speaker 56 that sort of describes, for example, a woman

Speaker 56 stating something about pleasure and intercourse and about kissing and so on.

Speaker 6 Sophie and Trolls reached out to Science, the journal that published the research paper about HSV-1, and asked if they could write an essay on what they'd found.

Speaker 34 What they argued is not that they had found the exact date people started making out, but that such a date is probably a lot older than academics had previously believed.

Speaker 56 The argument has been before that, okay, if it originated in India, then perhaps it spread from there.

Speaker 56 But I think now that we can push it back, I think it's now we can see a larger area that it's practiced in the ancient world.

Speaker 56 And I'm not so sure that it had one point of origin from where it like spread.

Speaker 3 If you take their paper and put it together with doctors Garcia and Jacobiaks, you end up having to hold on to two contradictory seeming ideas at the same time.

Speaker 10 That kissing is not innate, but it is ancient.

Speaker 6 There is a big complication in our ability to nail down just how ancient though.

Speaker 44 And it's that full human writing systems don't come much older than cuneiform.

Speaker 3 So if we want to figure out more about the ancient history of kissing, it's not going to come from text.

Speaker 55 Perhaps

Speaker 55 you know, a cave painting will emerge suddenly with people kissing. That would be awesome.
And then they can write a new perspective, an art perspective. That would be cool.

Speaker 16 But maybe we don't need this hypothetical cave painting maybe we already do have the means to learn more about the ancient history of kissing when we come back it's time to check in with some of our relatives

Speaker 21 hey it's mary harris host of slate's daily news podcast what next

Speaker 21 this week we're following the real-time collapse of public health in the u.s under donald trump's secretary of health and human Services. One of RFK Jr.'s long-standing targets has been vaccines.

Speaker 21 A porva Mandavili at the New York Times says he's trying to make it difficult for big pharma to make them available at all.

Speaker 59 Vaccines are not a moneymaker, and the only reason companies have stayed in the business is because of these protections, because of the guaranteed demand.

Speaker 59 If those things go away, they have zero incentive to stay and continue to make vaccines.

Speaker 21 Check out What Next, wherever you listen.

Speaker 20 Hey, it's Dan Coyce from Slate. I made a new word game, and I hope you'll come try it out.
It's called Pears, like the fruit, pears.

Speaker 20 I wanted to make a word game that rewards not only random-ass scrabble words, but the fun words that we use in our real lives. Tankini, Dillweed, Gloopy, Twink.

Speaker 20 We'll post a new game every day, and your job is to make as many words as you can, to find great pair words, and of course, to beat your friends.

Speaker 20 If that sounds like you're kind of fun, head to slate.com slash games to find pears today. That's slate.com slash games and look for pears.

Speaker 25 So there are a number of living animals with whom we share 98.8% of our DNA and a common ancestor.

Speaker 12 They are the great apes, and they include gorillas, orangutans, chimpanzees, and bonobos.

Speaker 6 Bonobos are particularly famous for one thing.

Speaker 60 Bonobos makes sex into everything they do.

Speaker 6 Dr. Franz Duvall is a primatologist and biologist who studies bonobos.

Speaker 60 They have sexual activities in all combinations of individuals. So male-male, female-female, male-female, adults with youngsters.
All combinations occur. And it's usually fairly brief.

Speaker 2 And bonobos, sexy kiss.

Speaker 60 One bonobo places its mouth on the other. And then you can see that their tongues are moving in and out, and

Speaker 60 they may keep that up for a couple of seconds. I've seen it more among juveniles, so in a playful context.
So

Speaker 60 there's always an erection or something going on.

Speaker 37 Dr.

Speaker 24 Duvall was pretty clear that bonobo kissing, even with the erections, is largely friendly.

Speaker 12 Still, the erections make the bonobo tongue kissing seem at least a little sexual.

Speaker 44 And because bonobos are so closely related to us, with that 98% shared DNA and all, they're often bandied about as a sign that this behavior might also be innate in humans.

Speaker 36 Like if bonobos are apparently hardwired to sexy kiss, why not us?

Speaker 27 But to find the counter-argument, look no further than chimpanzees.

Speaker 26 Because chimps, who are an equally close relative to us, do not sexy kiss. Though Dr.

Speaker 9 Duvall, who also studies chimps, says they do kiss like us in other ways.

Speaker 60 It may be on the mouth of somebody else, but it may also be on a shoulder, on a leg, on their back. And it's more like a little no.
They pant when they do it.

Speaker 60 And it's usually done in greeting after a long absence, so they embrace and they kiss, or in reconciliation after a fight.

Speaker 60 So those two functions, kissing and reconciliation, and greeting, is of course something they have in common with us.

Speaker 24 I think this variation in the great apes supports the idea not that sexy kissing is programmed into humans, but that you'd expect to see some variation in humans too.

Speaker 45 Some of us sexy kiss and some of us only affiliative kiss.

Speaker 37 But either way, Dr. Naval thinks both behaviors are really old.

Speaker 60 It's probably a couple of million years old. Anthropologists and psychologists, they look at humanity as if we exist 20,000 years and that's it, so to speak.

Speaker 60 But, you know, our species exists 300,000 years and that's just our species.

Speaker 16 And now we're going to turn to another species that might be able to give us our oldest clue about kissing yet.

Speaker 36 Dr.

Speaker 28 Laura Weyrich is an associate professor of anthropology and bioethics at Penn State.

Speaker 58 I study the microbes that live in the mouth.

Speaker 3 A microbe is a tiny single-celled organism and you have a hundred trillion of them living in your body.

Speaker 16 All your microbes together make up your microbiome.

Speaker 3 You might have heard about your microbiome in relation to gut health, but Laura says what's living in your mouth is just as important.

Speaker 58 What we see over time is that the types of microbes in our mouth have changed pretty dramatically when we adapt different lifestyles, when we move to different places on the planet, when we eat different foods, and potentially maybe even when we interact with other people.

Speaker 26 And they can see all of this by cleaning ancient teeth.

Speaker 3 Think of the plaque you get on your teeth that gets cleaned off every time you go to the dentist.

Speaker 24 Now imagine you're an ancient human living thousands of years ago who doesn't have a dentist.

Speaker 31 That plaque will build up and up into an almost cement-like substance called dental calculus.

Speaker 58 If you pop off the dental calculus from the teeth, you can put that under a microscope and see what bacteria, viruses, archaea, protists, fungi, whatever it is that they had living in their mouths back in time.

Speaker 7 Her lab takes the dental calculus and separates out all the fragments of DNA in it, human and microbial, and sequences them to figure out what was in ancient mouths.

Speaker 31 And in the mid-2010s, her lab got interested in what was happening around 8,000 years ago when agriculture arrived in Europe.

Speaker 58 We wanted to understand whether or not that impacted the microbiome because the diet shifts dramatically.

Speaker 6 But it turned out to be really hard to get access to a European skeleton from before the introduction of agriculture.

Speaker 58 So what we ended up doing was using Neanderthals as proxies for human hunter-gatherers that lived in Europe at the same time.

Speaker 57 I also like that it's Neanderthal, like not Neanderthal.

Speaker 61 Like are we just all saying it wrong?

Speaker 58 Yeah, there's a big debate even within our field.

Speaker 61 Neanderthal sounds sophisticated. Yeah.

Speaker 6 Pronunciation aside, using Neanderthals as a stand-in for humans might seem like a bit of a leap. We have tended to be pretty dismissive of Neanderthals.

Speaker 37 They died out about 40,000 years ago.

Speaker 36 And when their bones were first discovered in the mid-19th century, their heavy brows and bone density had Victorians declaring them ape-like cave dwellers.

Speaker 6 An idea that has persisted.

Speaker 56 It's so easy to use Geico.com, a caveman could do it. Not cool.

Speaker 22 That's an advertisement for the insurance company in which a caveman who looks a lot like a Neanderthal, strong brow, beard, long hair, storms off after being so insulted.

Speaker 44 The commercial would go on to inspire a short-lived sitcom and a long-running ad campaign.

Speaker 1 Historically, you guys have struggled to adapt.

Speaker 62 Yeah, right. Walking upright, discovering fire, inventing the wheel, laying the foundation for all mankind.
You're right. Good point.
Sorry we couldn't get that to you sooner.

Speaker 28 And this caveman in the Geico ad has a point about Neanderthals, too.

Speaker 3 In recent years, scientists have shown that Neanderthals were sophisticated and engaged in a lot of the cultural practices we like to think of as distinctly human.

Speaker 32 Most of all, they intermingled and mated with us. Neanderthal DNA can be found in some modern human genomes.

Speaker 37 So it seemed to Laura and her team that Neanderthal teeth might be a good stand-in for pre-agricultural humans.

Speaker 58 They're also hunting and gathering, and they're probably doing things very similar to anatomically modern humans.

Speaker 37 So they did what they do.

Speaker 27 They popped that Neanderthal dental calculus right off, separated all the fragments of DNA out of it, and looked at the microbes they found, hoping to learn something about what agriculture did to our diet.

Speaker 16 And lo and behold, Something else snuck up on them instead.

Speaker 58 When we started comparing the microbes in humans versus Neanderthals, we found that humans and Neanderthals were probably swapping microorganisms, especially the ones in the mouth, about 120,000 years ago.

Speaker 24 120,000 years ago is not just some random number.

Speaker 26 By then, Neanderthals and humans were definitely mating.

Speaker 58 If you know people are interbreeding, you know people are having sexual relationships, and now you know they're swapping oral microorganisms, there is a tendency to think, oh my gosh, that must be because of kissing.

Speaker 3 Dr.

Speaker 6 Weyrich is quick to point out that you can swap mouth germs in all sorts of ways, sharing food and water sources, and you you can also get them from your relatives.

Speaker 26 So, if you were the progeny of a Neanderthal and a human, you would get both of their microbes.

Speaker 58 So, there's lots of different ways that this could happen. It doesn't have to be kissing, but one of the options is kissing.

Speaker 38 It doesn't rule out kissing.

Speaker 19 So, it's not that hypothetical cave painting showing prehistoric canoodling.

Speaker 34 But it's pretty good.

Speaker 22 There's one more question I want to ask about the sexy kiss.

Speaker 24 Why do we do it?

Speaker 7 I mean, it is really just taking your slimy germy mouth and putting it on someone else's slimy germy mouth and exchanging something like 80 million bacteria.

Speaker 36 And yet that feels good.

Speaker 23 Why?

Speaker 16 There's no one answer here, and evolutionary biologists have developed a bunch of theories about it.

Speaker 11 Like besides just feeling good and increasing arousal, as I mentioned earlier, it does give you information about the health of a potential mate.

Speaker 31 But the idea I was most taken with came from the primatologist Franz Duvall, who thinks primates have a whole host of kissing-like behaviors called vulnerable contact behavior.

Speaker 60 So, for example, chimpanzees, when

Speaker 60 males are aroused because of some frightening sounds that they hear or they hear the neighbors who are enemies of them, they may touch each other's testicles, the males.

Speaker 60 And so that's actually vulnerable contact behavior because that's not a part of your body that you normally want to be touched by, certainly not by potential competitors.

Speaker 28 There's another example I found even more compelling in some other primates: monkeys.

Speaker 60 In Costa Rica, capuchin monkeys stick fingers up the noses of each other and sit like that for half an hour. They say it's actually a proof of trust between them.

Speaker 60 They're trying to prove that you can trust the other.

Speaker 60 But we have that kind of contact behavior.

Speaker 3 And maybe the kissing,

Speaker 60 tongue kissing, at least, where you exchange saliva and so on, which is I think vulnerable contact behavior,

Speaker 60 arose as a sign of trust, like I trust you and I can kiss you, something like that.

Speaker 26 Maybe kissing is like a much lovelier version of monkeys sticking fingers in each other's noses.

Speaker 39 It doesn't really make sense.

Speaker 3 And it's precisely the not making sense.

Speaker 26 That's the reason we do it. It gives the whole act meaning.

Speaker 39 It draws you close to the person that you're kissing.

Speaker 6 It can be startling to learn kissing is a cultural practice, that it comes out of where we're born and raised and live because it feels every bit as bedrock as nature ever does.

Speaker 19 But this is also by far the most romantic thing about it.

Speaker 26 We don't sexy kiss because we have to.

Speaker 19 We don't do it because we've been biologically preordained.

Speaker 19 We can just do it because we want to.

Speaker 5 I can't imagine like going through life and just like not kissing.

Speaker 24 This is Decodering.

Speaker 14 I'm Willa Paskin.

Speaker 25 If you have any cultural mysteries you want us to decode, you can email us at decodering at slate.com.

Speaker 3 This episode was written by me, Willa Paskin.

Speaker 24 I produced Decodering with Katie Shepard.

Speaker 3 This episode was edited by Andrea Bruce and Joel Meyer.

Speaker 15 Derek John is Slate's executive producer of narrative podcasts, and Merrick Jacob is senior technical director.

Speaker 25 Thank you to Marcel Denesi.

Speaker 3 If you're interested in the papers we mentioned and that explicit Bronze Age sculpture, we will link to them on our show page.

Speaker 37 If you haven't yet, please subscribe and rate our Feed and Apple podcasts or wherever you get your podcasts.

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Speaker 24 We'll see you next week.

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