0:00

Apple Card is different. It has a cashback

0:02

rewards program unlike other cards.

0:05

You earn unlimited daily cash back on

0:07

every purchase, receive it daily, and can grow

0:09

it at 4.15% annual percentage yield when

0:13

you open a high-yield savings account. Apply

0:16

for Apple Card in the Wallet app on iPhone

0:19

and start earning and growing your daily

0:21

cash with savings today. Apple

0:23

Card is subject to credit approval. Savings

0:26

is available to Apple Card owners subject

0:28

to eligibility requirements. Savings

0:31

accounts provided by Goldman Sachs Bank

0:33

USA. Member FDIC.

0:35

Terms apply.

0:42

When Shana Roth was in 10th

0:44

grade, she set her mind to something.

0:47

I was like very determined to get kissed

0:49

soon. This was in Michigan in the mid-2000s,

0:52

but the thing driving Shana's determination

0:55

was 1980s teen movies. I

0:58

wanted that like John Hughes, you

1:01

know, nerdy girl gets good kind

1:03

of a romance. Maybe I saw 16 Candles

1:06

too often. 16 Candles

1:09

was written and directed by John Hughes,

1:11

and it ends with Molly Ringwald's character Samantha

1:14

sitting cross-legged in front of her birthday

1:16

cake, across from

1:17

her crush, the dreamy Jake

1:19

Ryan.

1:21

Happy birthday, Samantha. As

1:23

the music swells, they

1:27

lean towards one another. It

1:30

already came true. The

1:32

candles illuminating them from beneath, and

1:35

they kiss for the very first time. I

1:40

just was constantly thinking

1:42

of how to make something worthy

1:46

of a scene in a movie in my life.

1:48

So when Ben, a smart boy in her class with a

1:50

lot of floppy brown hair, asked her out,

1:53

it was game on. This guy's going to kiss

1:55

me. He doesn't know it yet, but this is going to happen for me. For

1:57

the date, Ben's dad dropped them off at the mall.

2:00

see Miracle, a movie about the unexpected

2:02

triumph of the 1980 US

2:05

men's Olympic hockey team.

2:06

What are you playing for?

2:08

USA! I don't know

2:10

why we saw this movie. Like, I don't

2:13

care about hockey. During the movie,

2:15

Shana spent a lot of time thinking about exactly

2:17

what she wanted to happen after. I had

2:20

a line that I was like, I'm going to use this

2:22

line, and this is how I'm going to get kissed. And

2:24

it's going to be perfect. So, credits

2:26

are rolling. It's playing that,

2:29

that sing with them, sing running

2:31

in. Sing with me, sing

2:33

for the year, sing for the love,

2:36

sing for the tears. Aerosmith,

2:38

there you go.

2:43

Theater empties out, and we're just kind of sitting there,

2:45

just kind of, okay, what do we do now? And I look at him,

2:47

and I go, so, are you going

2:50

to kiss me on this date, or do I have to do everything

2:52

myself? That was the

2:54

line she had planned.

2:56

I mean, I must say, I executed it perfectly.

2:58

And so he kind of, like, looked at me, obviously

3:01

stunned, and we kissed.

3:12

And we even kissed again when he dropped

3:14

me off and walked me to the door. Shayna

3:17

had done it. She had successfully

3:19

arranged this monumental rite

3:21

of passage, this step towards

3:24

adulthood. She and Ben would

3:26

even date for a couple of months and make

3:28

out sometimes. For Shayna, who's

3:30

now a senior producer at Slate, it

3:32

was the beginning of a life full

3:34

of kissing.

3:36

I can't imagine, like, going through life, I guess, especially,

3:38

like, as a teenager, and just, like, not kissing.

3:40

What if I told you that, like, in all

3:43

the cultures all around the

3:45

world, in, like, half of them,

3:48

people don't kiss like you did.

3:51

Wait,

3:51

what? This

3:59

is Decoder. I'm Willa Paskin. Kissing,

4:02

romantic, sexual, steamy, smooching,

4:05

is so ingrained in our desires, habits,

4:07

and culture, it seems like a fact

4:09

of life. Like breathing or eating,

4:12

we just do it. But what

4:14

if it's not like that

4:15

at all? In this episode, we're going

4:17

to look at passionate kissing, dispassionately.

4:21

Not as something instinctual and innate, but

4:23

as a cultural practice with a history

4:26

of its own. We're going to follow the

4:28

kiss backwards in time, trying

4:30

to find its origins, and turning up

4:32

surprises along the way. So

4:35

today on Decoder Ring, with

4:37

the help of apes, Neanderthals, herpes,

4:40

and Bronze Age pornography, how

4:44

long have we been kissing?

4:57

At the end of your first

5:01

year,

5:12

Discover credit

5:14

cards automatically double all the

5:16

cash back that you've earned. That's

5:19

right. Everything you earned doubled. All

5:22

the cash back from eating at your favorite soup

5:24

dumpling restaurant doubled. All

5:26

the cash back from that trip where you sort of learned

5:28

to snowboard also doubled.

5:29

And the best part,

5:31

you don't have to do anything ridiculous to get it.

5:34

Nope. Discover does

5:36

it automatically. Seriously, though,

5:38

see terms and check it out for yourself at

5:40

discover.com slash match.

5:46

I want to start by defining the different

5:48

kinds of kisses. And I don't mean

5:50

good kisses or bad kisses, sloppy

5:52

kisses or tongue kisses. I mean,

5:55

scientific

5:56

kisses. There are actually many

5:58

categories of kisses. Emma Imbler

6:00

is a science writer at Defector. I

6:02

mostly write about creatures, but humans

6:05

are creatures as well. And

6:07

there is one kind of kissing we human

6:09

creatures do more than any other. There's

6:12

like the friendly kiss, which happens between

6:14

friends, oftentimes between parents

6:17

and children or other family members. This

6:19

is one of a number of affiliative

6:22

kisses, kisses that are about forming

6:24

and creating social bonds, not

6:26

doing anything erotic. And this

6:28

friendly kiss, which doesn't even have

6:30

to be lip to lip, is something that

6:32

humans everywhere do. Platonic

6:36

kissing, like that happens between a parent

6:38

and a child, is universal. It's found

6:40

in every human culture.

6:42

Humans everywhere, in other words,

6:44

smooch on their babies. But there's

6:46

other kinds of affiliative kissing too.

6:48

There's also like, they call it

6:51

a submissive kiss, which sounds

6:53

very kinky, but it's just kind of like in

6:55

historical societies where like people would

6:58

kiss the feet of like a ruler that would be

7:00

like a submissive kiss. And we still do

7:02

a version of this, like when subjects kiss the

7:04

hand of the queen or Catholics kiss

7:06

the Pope's ring. There's also kisses

7:08

that are used as a greeting, like how French

7:10

people often kiss each other on both cheeks.

7:13

This kind of kiss isn't sexual either.

7:16

But of course, there is a kind

7:18

of kiss

7:19

that is. So

7:22

there's the romantic sexual kiss, which basically

7:24

just means like kiss that

7:26

accompanies romantic or sexual interest

7:28

or both.

7:29

It's thought that this kind of mouth to mouth kiss

7:31

evolved out of affiliative kissing.

7:34

Basically because our mouths are so sensitive,

7:37

some people started to use them in a more erotic

7:39

way. And the romantic sexual

7:42

kiss was born. A kiss that

7:44

Sabrina has more succinctly termed

7:47

the sexy kiss. I feel like sexy

7:49

kiss really encompasses everything.

7:52

And it's this type of kiss that is such

7:54

a big deal

7:55

in our culture.

8:04

It's such a dominant script, what researchers

8:06

call sexual script, for us, that kissing is

8:08

part of courtship. Dr. Justin Garcia

8:11

is the executive director of the Kinsey

8:13

Institute at the University of Indiana.

8:16

Especially in the current modern moment,

8:18

I mean, you can't put on a movie about romance

8:20

that there's not kissing involved, right? I believe

8:22

in long, slow, deep, soft, wet

8:25

kisses that last three days.

8:26

Kevin Costner talking about getting

8:29

to first base in the baseball romantic comedy

8:31

Bull Durham. So much.

8:34

Over the years, kissing has come up often in Justin's

8:36

work, and as he looked at it more closely, he

8:39

learned there were lots of theories about why

8:41

we do it. Like to increase intimacy

8:44

and arousal, and to get conscious and

8:46

unconscious hormonal and biological

8:48

cues about the health of our potential mates.

8:51

We also realized there was an assumption

8:54

underlying all of these

8:56

theories. We take for granted

8:59

that everyone must do it, that it must be, you know,

9:01

adaptive, it must have evolved. So

9:04

really the question was, well, actually, is that first

9:06

assumption true? Is everyone really doing this?

9:09

He thought we probably were, that all humans

9:11

sexy kiss, but he wanted to do a proper

9:13

academic study to nail it down.

9:16

So Justin emailed me and

9:18

he said, I think this is a

9:20

universal, why don't we just document

9:23

it? Dr. William Jankobiak is a professor

9:26

of anthropology at the University of

9:28

Nevada, Las Vegas. He's done

9:30

a number of cross-cultural studies where

9:32

you look at a wide array of research to try and

9:34

suss out a pattern. And that's exactly

9:37

what Justin wanted him to do in

9:39

order to determine whether or not romantic

9:41

sexual kissing actually is

9:44

universal. And I thought, yeah,

9:46

makes sense to me. So they started pouring

9:49

over the ethnographic literature. Studies

9:51

anthropologists have written about hundreds of cultures,

9:54

some in the past, some in the present, looking

9:56

for mentions of romantic sexual kissing.

9:59

expecting to find them all over

10:02

the place. And they did. In

10:05

one particular kind of

10:07

society. In complex

10:10

state civilizations,

10:12

societies, ising

10:14

is universal. A complex state

10:17

civilization is one with laws and hierarchies

10:19

and trade and agriculture that can

10:21

support millions of people. So

10:24

it's one like our own. These

10:26

kinds of societies are not new. Rome,

10:29

Egypt, Babylon, Japan, Imperial China

10:31

were also complex civilizations.

10:34

And they had kissing too. Most

10:36

people in the world today live in

10:38

a society like this, which is to

10:41

say they live in a society

10:43

with romantic sexual kissing, even

10:46

if it's only practiced in private

10:48

spaces. This is why it feels

10:50

like this kind of kissing is everywhere. But

10:52

complex civilizations are not the only

10:55

way humans can arrange

10:56

themselves. And as Justin and

10:58

Bill began looking into smaller societies,

11:01

romantic sexual kissing got

11:03

harder to find.

11:05

As I started reading through the ethnographers,

11:09

I wasn't getting any of the data. Particularly

11:11

when you're looking at old research,

11:13

it could be an oversight. In

11:15

other words, it was there, but no one ever commented

11:18

on it. You'd be hard pressed

11:20

looking at the entire thousand articles

11:23

and books on China for someone

11:25

to mention they use chopsticks.

11:27

It's so ubiquitous, you don't write on

11:30

it because everybody knows they use chopsticks.

11:32

So perhaps kissing was that as well.

11:35

So they started reaching out to anthropologists

11:37

who are experts in what used to be called hunter-gatherers

11:40

and are now called foragers. Basically

11:43

migratory societies, about 15 to 40 people.

11:46

I asked them, did you see any kissing?

11:49

And everyone said no. And

11:51

now that really became very enlightening.

11:54

And I thought, my goodness, we're really

11:56

documenting the opposite of our opening

11:58

hypothesis.

11:59

They next reached out to ethnographers of slightly

12:02

larger societies, living in groups of about 100 to 200

12:04

people. And

12:06

now they started to see more of

12:08

a split. Some of these cultures

12:11

had romantic sexual kissing,

12:14

but others didn't. It wasn't

12:16

that sex and romance and love were

12:18

unknown in these societies. It's

12:21

just that mouth kissing wasn't

12:23

a component of them. Though

12:25

an ethnographer studying a group living in the Amazon

12:28

did notice something else.

12:29

A lot of it was kind of graphic and nibbling

12:31

on each other's eyebrows, but

12:34

there was no kissing. So they

12:36

were sucking on eyebrows but not lips.

12:39

Dr. Garcia really got the goods when he came

12:41

across an opinion expressed by a woman in

12:43

one of the groups that doesn't kiss.

12:45

I remember reading this one piece from

12:48

an Aboriginal woman in Australia

12:51

and made a comment of asking,

12:53

if you like someone, why would you spit in their

12:55

mouth?

12:56

All told, they looked at 168 distinct

12:59

cultures from all over the world, the

13:02

Arctic to the tropics and in between,

13:05

and they found that just 46% engaged

13:09

in romantic sexual kissing.

13:11

Less than a half. That was a surprise

13:13

to us. We thought the number was going to be a lot higher. I

13:15

thought it was a universal and then no,

13:18

it's not. There was an assumption, this

13:21

sort of classic ethnocentrism, that

13:23

we think what we see in our societies is

13:25

true of societies all around the world. And we found no,

13:28

the answer is

13:28

no. Their findings suggest that romantic

13:30

sexual kissing is not genetically hardwired.

13:33

Otherwise, everyone would do

13:36

it. It's nurture, not

13:38

nature.

13:39

But for people who do sexy kiss,

13:41

there are benefits.

13:43

When you put a face close to another face, you get

13:45

all, you can see someone, you smell them, you feel

13:47

them, you taste them. You get a lot of sensory

13:49

information.

13:50

Some of that sensory information may even

13:53

register subconsciously. When we kiss

13:55

someone, we're getting their pheromones and information

13:57

about their health. And that data might

13:59

help us to...

13:59

whether we want to keep kissing

14:02

them. But even if kissing is

14:04

useful and pleasurable, Dr.

14:07

Garcia thinks...

14:08

Probably in the sense of where it emerged

14:10

from, that we've been doing it forever

14:12

is probably just not true. So if we haven't

14:15

been sexy kissing forever, just

14:17

how long have we been doing it? When

14:20

we come back, we're going to talk to a couple who

14:22

came up with an answer to this question

14:25

while talking about it over dinner.

14:30

Apple Card is different. It has a cash

14:32

back rewards program unlike other

14:34

cards. You earn unlimited daily cash

14:36

back on every purchase, receive it daily,

14:39

and can grow it at 4.15% annual percentage yield when

14:43

you open a high yield savings account. Apply

14:46

for Apple Card in the Wallet app on iPhone

14:49

and start earning and growing your daily

14:51

cash with savings today. Apple

14:53

Card is subject to credit approval. Savings

14:56

is available to Apple Card owners subject

14:58

to eligibility requirements. Savings

15:01

accounts provided by Goldman Sachs Bank

15:03

USA. Member FDIC.

15:05

Terms apply. I

15:25

can show you, but it will cost you $3. What?

15:29

Time and robbery. Who said that? Disney's

15:31

Haunted Mansion, ready PG-13, may be inappropriate

15:34

for children under 13. Only in theaters July 28. Get

15:36

tickets now.

15:38

Sophie Lund Rasmussen is a Danish

15:41

biologist and zoologist. I'm

15:44

actually an expert on the

15:46

research on European hedgehogs.

15:49

The noises you're hearing are hedgehogs

15:51

huffing and snuffling. I've

15:54

always loved hedgehogs. She's married

15:56

to Trolls Punk Arbel.

15:58

I'm an assistant professor in the United States. in astrology

16:01

at the University of Copenhagen. A seriologist

16:03

studied cuneiform, one of the earliest

16:06

scripts in world history. It originated

16:08

around 3,200 BCE in

16:10

modern day Iraq and Syria, a few hundred

16:12

years before the pyramids in Egypt, so

16:15

a little more than 5,000 years ago.

16:16

If you see a cuneiform

16:18

tablet, can you just read it? It

16:21

depends a bit on the genre. Some genres

16:23

you can sort of read. Then there

16:25

are some unique cases where it's much more

16:27

difficult and requires years of looking at

16:29

the same lump of clay.

16:31

It's an obscure field to

16:33

most of us, but when Sophie and trolls

16:35

met for the first time at a bar and he tried to

16:37

explain what he did, Sophie

16:40

lit up.

16:41

People don't know what he's doing, right? And

16:43

I was like, oh, so you study a seriology?

16:46

How did Sophie, a hedgehog expert,

16:49

know so much about a seriology? Sophie

16:51

was originally a Near Eastern archaeologist.

16:54

So I was the first person who ever knew what

16:56

he was actually doing. Sophie and trolls

16:58

have now been married for 12 years. And during

17:00

that time, they never thought much

17:02

about kissing,

17:04

except you know. Do you guys like kissing? Yes,

17:09

we do. Like everybody

17:11

else. That

17:13

just took it for granted that that was a completely

17:16

natural behavior, that

17:18

everybody practiced kissing. And

17:21

of course kissing was a very old practice.

17:24

Then one night at home,

17:25

over dinner, it came up. We

17:28

are a very nerdy couple, right? And

17:31

so it was just, you know, down to, so

17:33

did you notice that paper that came out the

17:35

other day? This was really interesting. That

17:37

paper was about herpes. Herpes, more

17:40

officially, the herpes simplex virus,

17:42

or HSV1, can create cold

17:45

sores on your mouth. And it's so common today

17:47

that about 3.7 billion people

17:50

carry it. That's half the global population.

17:53

And the paper, which was published in the academic

17:55

journal Science in July of 2022,

17:58

laid out research about... when

18:00

HSV-1 had started to conquer

18:02

the world. To do that, it

18:05

sequenced four herpes genomes taken

18:07

from the teeth of ancient European

18:09

skeletons. It found that there had been a

18:12

real shift in HSV-1 dominance

18:14

in Europe around 5,000 years ago during

18:17

the Bronze Age. It also included

18:19

a hypothesis about why that

18:21

shift might have happened.

18:25

That shift might have occurred because there

18:27

had been a migration and people

18:30

had perhaps introduced sexual romantic

18:32

kissing into Europe. And that could

18:35

then have led to the spread of this herpes

18:37

simplex virus 1 and

18:39

sort of accelerated it. Herpes

18:41

is spread by, among other

18:43

things, kissing and sex to

18:45

this day. So it seemed possible

18:48

these same acts had helped spread it in the past.

18:51

But sitting at dinner, Sophie

18:54

and Scholes realized they were both a

18:56

little surprised by the idea

18:58

that romantic sexual kissing was

19:01

ever new. Why was the paper hypothesizing

19:04

that it had only arrived in Europe some

19:07

thousands of years ago?

19:08

What was the evidence for that?

19:11

So we read the article and

19:14

sort of stumbled upon in the supplementary

19:17

materials that the reference

19:19

they cited as the earliest

19:21

evidence for this romantic sexual kiss

19:24

was allegedly from India.

19:26

This has been the academic consensus

19:28

for years that the first documented

19:31

appearance of romantic sexual kissing

19:33

is in written Sanskrit texts from

19:35

around 1500 BCE, about 3,500 years ago.

19:40

No one thinks this was the first kiss,

19:43

but it is considered the first documented

19:46

one. And so the hypothesis

19:48

was herpes could have spread

19:51

from South Asia as migration

19:54

occurred.

19:55

When Scholes saw this theory,

19:57

his aesthesiologist sense went off. And

20:01

trolls went, I honestly think I can

20:03

beat that with a thousand years. And

20:07

then we had to go to the office

20:09

and look after dinner to double

20:11

check.

20:13

That night, instead of dessert, they

20:15

read ancient cuneiform references to

20:17

romantic sexual kissing, some of

20:19

which go back 4,500 years. That's

20:22

a thousand years older than the Sanskrit

20:24

text mentioned in the Herpes paper. Most

20:27

early cuneiform texts are administrative,

20:29

but important slices of ancient life appear

20:32

in them, even personal stuff.

20:34

And you then get, for example,

20:36

this bizarre lawsuit-like

20:39

legal text that has to do with a

20:42

woman swearing to refrain having sexual

20:44

relations to another man that she had

20:46

sexual relations to before but they're not married.

20:48

And there, you know, kissing is also

20:50

mentioned in relation to this intimacy.

20:54

There's also a stone slab that shows a couple

20:56

locked in an embrace. The woman's

20:58

leg is lifted over the man's hip

21:00

and they're clearly having sex and

21:03

also clearly kissing.

21:05

And we also have some what

21:07

you could call erotic literature that

21:10

sort of describes, for example, a woman

21:14

stating something about pleasure

21:16

and intercourse and about

21:18

kissing and so on.

21:19

Sophie In trolls reached up to Science,

21:22

the journal that published the research paper about

21:24

HSV-1, and asked if they could write

21:26

an essay on what they'd found. What

21:29

they argued is not that they had found the

21:31

exact date people started

21:33

making out, but that such a date is

21:35

probably a lot older than academics

21:38

had previously believed.

21:40

The argument has been before that,

21:43

OK, if it originated in India, then

21:45

perhaps it's spread from there. But I think

21:47

now that we can push it back, I think it's

21:50

now we can see a larger area that it's practiced

21:52

in the ancient world. And I'm not so

21:54

sure that it had one point

21:56

of origin from where it like spread.

21:59

and put it together with doctors

22:02

Garcia and Jacobiacs, you end

22:04

up having to hold onto two contradictory

22:07

seeming ideas at the same time.

22:10

That kissing is not innate, but

22:13

it is ancient. There

22:15

is a big complication in

22:17

our ability to nail down just how

22:20

ancient though. And it's that full human

22:22

writing systems don't come much older

22:25

than cuneiform. So if we

22:27

want to figure out more about the ancient

22:29

history of kissing,

22:30

it's not going to come from text.

22:32

Perhaps

22:35

a cave painting will emerge suddenly

22:38

with people kissing. That would be awesome.

22:41

And then they can write in your perspective, in

22:43

our perspective. That would be cool. But

22:47

maybe we don't need this hypothetical cave

22:49

painting. Maybe we already do

22:52

have the means to learn more about the

22:54

ancient history of kissing. When

22:56

we come back,

22:57

it's time to check in with some of our relatives.

23:29

I like to laugh. I

23:31

like to meet people who can make

23:33

me laugh. Please subscribe.

23:36

No.

23:40

So there are a number of living animals with

23:42

whom we share 98.8% of our DNA and a common ancestor.

23:47

They are the great apes. And they

23:49

include gorillas, orangutans, chimpanzees,

23:52

and bonobos.

23:54

Bonobos

23:58

are particularly famous for one. one thing. But

24:01

I was mixed sex into everything they do. Dr.

24:03

Franz de Waal is a primatologist and

24:06

biologist who studies bonobos.

24:08

They have sexual activities in all combinations

24:10

of individuals. So male, male, female,

24:13

female, male, female, adults

24:16

with youngsters. All combinations occur. And

24:19

it's usually fairly brief.

24:22

And bonobos, sexy kiss.

24:25

One bonobo places its mouth on the other.

24:28

And then you can see that their tongues

24:30

are moving in and out.

24:31

And they may keep that up for

24:34

a couple of seconds. I've seen it more

24:36

among juveniles, so in a playful

24:38

context. So there's

24:40

always an erection or something going on.

24:44

Dr. de Waal was pretty clear that bonobo

24:46

kissing, even with the erections,

24:49

is largely friendly. Still,

24:51

the erections make the bonobo tongue kissing

24:53

seem at least a little sexual.

24:56

And because bonobos are so closely related

24:59

to us, with that 98% shared DNA and all, they're

25:03

often bandied about as a sign

25:05

that this behavior might also be innate

25:08

in humans. Like if bonobos

25:10

are apparently hardwired to sexy

25:12

kiss,

25:14

why not us?

25:16

But to find the counter-argument, look no

25:18

further than chimpanzees.

25:19

As chimps

25:21

who are an equally close

25:23

relative to us do not sexy

25:26

kiss. Though Dr. de Waal, who also

25:28

studies chimps, says they do kiss

25:30

like us in other ways.

25:33

It may be on the mouth of somebody else,

25:35

but it may also be on the shoulder, on

25:37

the leg, on the back. And

25:40

it's more like a little gnaw. They panned

25:42

when they do it.

25:44

And it's usually done in greeting

25:46

after long absence, so they embrace and

25:48

they kiss. Or in reconciliation

25:51

after a fight. So those two functions, kissing

25:54

in reconciliation and greeting, is of course something

25:56

they have in common with us.

25:59

the Great Ape supports the idea

26:02

not that sexy kissing is programmed

26:04

into humans, but that you'd expect

26:07

to see some variation in humans

26:09

too. Some of us sexy kiss

26:12

and some of us only affiliative kiss.

26:14

But

26:14

either way, Dr. Duvall thinks

26:17

both behaviors are really

26:20

old. It's probably a couple of million years old.

26:22

Anthropologists

26:24

and psychologists, they look

26:26

at humanity as if we

26:28

exist 20,000 years, and that's it,

26:30

so to speak. But, you know, our species

26:33

exists 300,000 years, and that's just

26:36

our species.

26:37

And now we're going to turn to another species

26:39

that might be able to give us our oldest clue

26:41

about kissing yet. Dr.

26:43

Laura Weyrich is an associate professor of anthropology

26:46

and bioethics at Penn State. I

26:49

study the microbes that live in the mouth.

26:52

A microbe is a tiny single-celled organism,

26:55

and you have a hundred trillion of them living in

26:57

your body. All your microbes together

26:59

make up your microbiome. You might have heard

27:01

about your microbiome in relation to gut health,

27:04

but Laura says what's living in your mouth is just

27:06

as important.

27:08

What we see over time is that the types

27:10

of microbes in our mouth have changed pretty dramatically

27:12

when we adapted different lifestyles, when

27:14

we moved to different places on the planet, when

27:17

we eat different foods, and potentially

27:20

maybe even when we interact with other people. And

27:23

they can see all of this by cleaning

27:26

ancient teeth. Think of the plaque

27:28

you get on your teeth that gets cleaned off every

27:31

time you go to the dentist.

27:34

Now imagine, you're an ancient human

27:36

living thousands of years ago who doesn't

27:39

have a dentist. That plaque will build

27:41

up and up into an almost cement-like

27:43

substance called dental calculus.

27:46

If you pop off the dental calculus from the

27:48

teeth, you can put that under a microscope and

27:50

see what bacteria, viruses, archaea,

27:53

protists, fungi, whatever it is that

27:55

they had living in their mouths back

27:57

in time.

27:58

Her lab takes the dental

27:59

calculus and separates out all the

28:02

fragments of DNA in it, human

28:04

and microbial, and sequences them

28:06

to figure out what was in ancient

28:08

mouths.

28:09

And in the mid-2010s, her lab got

28:12

interested in what was happening around 8,000

28:14

years ago, when agriculture arrived

28:17

in Europe.

28:18

We wanted to understand whether or not that impacted the microbiome,

28:20

because the diet shifts dramatically. But it

28:22

turned out to be really hard to get access

28:24

to a European skeleton from before

28:27

the introduction of agriculture.

28:29

So what we ended up doing

28:31

was using Neanderthals as proxies

28:34

for human hunter-gatherers that lived in Europe

28:36

at the same time.

28:37

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

28:39

Like, are we just all saying it wrong? Yeah,

28:42

there's a big debate even within our field. Neanderthal

28:45

sounds sophisticated. Yeah. Pronunciation

28:49

aside, using Neanderthals as

28:51

a stand-in for humans might seem like a bit

28:54

of a leap. We have tended to be pretty

28:56

dismissive of Neanderthals. They

28:58

died out about 40,000 years ago,

29:01

and when their bones were first discovered in

29:03

the mid-19th century, their heavy brows

29:05

and bone density had Victorians

29:07

declaring them ape-like cave dwellers,

29:10

an idea that has persisted.

29:12

It's so easy to use Geico.com,

29:15

a caveman could do it. Not cool.

29:18

That's an advertisement for the insurance company

29:20

in which a caveman who looks a lot like

29:22

a Neanderthal—strong brow, beard,

29:25

long hair—storms off after

29:27

being so insulted. The commercial would

29:29

go on to inspire a short-lived sitcom and

29:32

a long-running ad campaign. Historically,

29:34

you guys have struggled

29:36

to adapt. Yeah, right. Walking upright,

29:39

discovering fire, inventing

29:41

the wheel, laying the foundation for all mankind.

29:43

You're right. Good point. Sorry we couldn't get that to you

29:46

sooner.

29:47

And this caveman in the Geico ad

29:49

has a point about Neanderthals,

29:51

too. In recent years, scientists

29:53

have shown that Neanderthals were sophisticated

29:56

and engaged in a lot of the cultural practices

29:58

we like to think of as distinctly

29:59

human. Most of all,

30:02

they intermingled and mated with

30:04

us. Neanderthal DNA can be found

30:07

in some modern human genomes. So

30:09

it seemed to Laura and her team that

30:11

Neanderthal teeth might be a good

30:13

stand-in for pre-agricultural

30:15

humans.

30:16

They're also hunting and gathering, and they're probably doing

30:19

things very similar to anatomically modern

30:21

humans. So they did what they do. They

30:23

popped that Neanderthal dental calculus

30:25

write-off, separated all the fragments

30:27

of DNA out of it, and looked at

30:29

the microbes they found, hoping to learn

30:32

something about what agriculture did

30:34

to our diet. And low and

30:36

behold,

30:37

something else snuck up on them instead.

30:39

When we started comparing the microbes in humans versus

30:42

Neanderthals, we found that humans and Neanderthals were probably

30:44

swapping microorganisms, especially the ones

30:46

in the mouth, about 120,000 years ago. 120,000 years ago is not just some random

30:51

number. By then, Neanderthals

30:53

and humans were definitely

30:56

mating. If you know people are interbreeding,

30:58

you know people are having sexual relationships, and

31:01

now you know they're swapping oral microorganisms, there

31:03

is a tendency to think, oh my gosh, that must be because

31:06

of kissing. Dr. Weyrich is quick to point

31:08

out that you can swap mouth germs in all

31:10

sorts of ways, sharing food and water

31:12

sources, and you can also get them from your relatives.

31:16

So if you were the progeny of a Neanderthal

31:18

and a human,

31:19

you would get both of their microbes.

31:22

So there's lots of different ways that this could happen.

31:24

It doesn't have to be kissing, but one of the options

31:27

is kissing. It doesn't rule out kissing.

31:30

So it's not that hypothetical cave painting

31:32

showing prehistoric canoodling,

31:35

but it's pretty good. There's one more

31:37

question I want to ask about the sexy kiss. Why

31:40

do we do it? I mean, it is really just taking

31:42

your slimy, gerby mouth and

31:45

putting it on someone else's slimy, germy

31:47

mouth and exchanging something like 80 million

31:50

bacteria.

31:51

And yet, that feels good.

31:55

Why? There's no one answer here,

31:57

and evolutionary biologists have developed a bunch

31:59

of...

31:59

of theories about it. Like besides

32:02

just feeling good and increasing arousal, as

32:04

I mentioned earlier, it does give you

32:06

information about the health of a potential

32:08

mate. But the idea I was most

32:11

taken with came from the primatologist

32:13

Franz de Waal, who thinks primates have

32:15

a whole host of kissing-like behaviors

32:18

called vulnerable contact behavior.

32:21

So for example, chimpanzees,

32:24

when males are aroused

32:27

because of some frightening

32:29

sounds that they hear or they hear

32:31

the neighbors who are enemies

32:33

of them, they may touch each other's

32:35

testicles, the males. And so that's

32:37

actually vulnerable contact behavior because that's

32:40

not a part of your body that you normally want to

32:42

be touched by. It's certainly not by potential

32:45

competitors. There's

32:46

another example I found even more

32:48

compelling in some other primates,

32:51

monkeys. In Costa Rica, Capuchin

32:53

monkeys stick fingers up

32:55

the noses of each other and sit like that

32:58

for half an hour. They say it's actually

33:00

a proof of trust between them. They're

33:03

trying to prove that you can trust the other. But

33:06

we have that kind of contact behavior. And maybe

33:08

the kissing, tongue

33:10

kissing at least, where

33:12

you exchange saliva and so on, which

33:15

is I think vulnerable contact behavior, arose

33:19

as a sign of trust. Like, I trust

33:21

you and I can kiss you, something like

33:23

that.

33:24

Maybe kissing is like a

33:26

much lovelier version of monkeys

33:28

sticking fingers in each other's noses. It

33:30

doesn't really make sense. And

33:35

it's precisely the not making sense. That's

33:37

the reason we do it. It gives the

33:39

whole act meaning. It

33:42

draws you close to the person that you're

33:44

kissing. It can be

33:46

startling to learn kissing is a cultural practice, that

33:48

it comes out of where we're born and raised and live because

33:53

it feels every bit as bedrock

33:55

as nature ever does.

33:56

But this is also

33:58

by far the most common thing romantic

34:01

thing about it.

34:04

We don't sexy kiss because we have

34:06

to. We don't do it because we've

34:08

been biologically preordained.

34:12

We can just do it because

34:14

we want to. I

34:17

can't imagine going through life and just not

34:19

kissing.

34:33

This is Decoder Ring. I'm Willa Pasken.

34:35

If you have any cultural mysteries you want us to decode, you

34:37

can email us at decoderring at slate dot

34:39

com. This episode

34:41

was written by me, Willa Pasken.

34:44

I produced Decoder Ring with Katie Shepard. This episode

34:46

was edited by Andrea Bruce and Joel Meyer. Derek

34:50

John is Slate's producer. We're going

34:52

to be talking about how to make a decoder ring.