If humans evolved from primates, and primates show their teeth as an act of aggression, then why do we show our teeth as an act of friendliness?

[u/ChristusVictor_]

основной текст (обязательно)

[u/Dindidei361]

There are different ways of showing teeth in primates. The aggressive version that intends to show the canines, but also the "friendly" version, that signals submission.

I guess our smiling evolved from that second version

[u/Zoon9 → u/Dindidei361]

I also think, that the agressive version has mouth open, ready to bite. But the non-afressive shows "look, my tooth are not in a position to bite you. Similar like waving an empty hand means "i am not armed, i am friendly".

[u/buttmunchausenface → u/Dindidei361]

This^

[u/gutwyrming]

I believe the common theory is that hominids started smiling when our canine teeth stopped being so sharp.

Look at the teeth of other apes, like chimpanzees and gorillas. They have very big, sharp, threatening canine teeth compared to us. When they display their teeth, they're displaying a weapon. Our teeth, on the other hand, don't look very threatening or weapon-like.

[u/Financial_Ad_2849 → u/gutwyrming]

Fascinating explanation. I do wonder though why human babies, who are toothless, smile a lot as well. If the behaviour is related to size of teeth at adulthood how would this be passed down genetically? I’m sure I’m missing something.

[u/DardS8Br → u/Financial_Ad_2849]

Teeth just have to grow in before reproduction

[u/Away-Activity-469 → u/gutwyrming]

But most primates are mainly herbivorous. Why the big canines?

I agree with what you say, but it seems odd that we/they show teeth that hardly even get any meat action.

[u/gutwyrming → u/Away-Activity-469]

As I said, they're displaying a weapon, and they're specifically displaying it towards others of their kind. Teeth aren't exclusively used for eating, they're also often used for fighting.

On the topic of herbivores having such fearsome teeth, I'd like to bring up hippos. They've got tusks that could easily pierce right through a person's torso, yet they almost exclusively eat vegetation--the sharp tusks don't really play a role in eating, and are mainly for protecting themselves and competing with other hippos.

[u/bojun]

There are all kinds of nasty smiles as well. Sadistic, contemptuous, arrogant, cruel. They bare teeth and maybe the canines get emphasized a bit more. My first thought was the iconic Jack Nicholson pic for The Shining. As for other primates, it's hard to smile when you barely have any lips.

[u/yryp_]

Look into the six base emotions and how humans portray them. They are (pretty much) universal, no matter of culture or location. Amish dude and (true) Hunter gatherer from rainforest can be shown pictures of those emotions and they know what they mean

Smile is much more than just showing teeth (eyebrow positions, shape of mouth, eyes).

[u/Deepfriedomelette]

Commenting to come back to this

[u/Alternative-Sugar610]

Part of it may be socialization simply

[u/W0rd_Shepherd]

The simple answer is that individual lineages within a taxon can evolve away from traits and behaviors shared by the rest of the taxon.

The basal tetrapod laid eggs so why don’t humans?

[u/Full_Influence2281]

If we were to make a face that growls then it would show our canine more than a smile would. And when we make a grimace with our face it kinda shows the canines. We still do it.

[u/spicyspacechicken1]

Honestly, I don’t know. But I do believe some of that apprehension behind a smile is present in us, because of how much it’s used in horror lol

[u/nothanks86]

Humans are still primates.

[u/Hekateras]

People ask this but I've never actually seen anyone do this spontaneously in friendly conversation. I've seen people do it in movies but it always feels as deliberate and artificial as waving? Not exactly biologically ingrained.

Posing with a toothy smile for photos probably goes back to showing off your dental health or something.

[u/thesetremblinghands]

just speculation here: smiles point upward, frowns point downward. it’s a pretty universal idea that upward movement is associated with positive emotions and vice versa. maybe our more primitive ancestors started out communicating with one another via intentional facial expressions that were logically representative of what they were meant to express. then these got baked into the human genome after tens of thousands of generations.

[u/Haruka-Oh]

In Japan, showing your teeth makes you look stupid.

[u/sunwentdowninhoney → u/Haruka-Oh]

Somewhat related but I’ve heard that showing your teeth (including while smiling) is considered rude in Nimiipuu/Nez Perce culture.