Smiling prominently for portraits seemed to become more popular only after modern dentistry became common.

I imagine most people in the Middle Ages (and much later) had chipped, missing, buckled, crooked and stained teeth.

Now pristine teeth are a signal of wealth (even though they're usually 100% fake veneers, at least among actors and models) so people want to signal their wealth by smiling prominently.

Teeth in skeletons from the Middle Ages seem fine. It is later ones, after bringing sugar back from the Americas, that have lots of cavities and missing teeth.

Check out the thesis of the recent bestseller Breath by James Nestor. Native American and other traditional cultures put serious emphasis on nose breathing, strictly avoiding mouth breathing. Apparently, consistent nose-breathing can affect nasal and upper-palate development, favoring a spacious mouth and straighter teeth. It can also help avoid dry mouth at night, apparently favoring resistance to dental caries. There is a book by a 19th century ethnographer who discovered some of this, titled Shut Your Mouth and Save Your Life.[1]

[1] https://www.consciousbreathing.com/articles/shut-your-mouth-...

A couple of years ago I forced myself to sleep with my mouth shut. It helped undry me mouth. But, through my own pressure I started to be a heavy teeth grinder in the night. That’s definitely worse for me.

This is complete pseudoscience. The Sawbones podcast has a good overview of this idea: https://maximumfun.org/episodes/sawbones/mewing/

I listened to the podcast, which as it says focuses in particular on John Mew and son, John apparently being on the cruel and crank end by experimenting on his children including on his daughter with expected negative results, and his son now reportedly showing a flair for bringing pseudosciency selective evidence to promotion on social media, and more recently perhaps helping "incels" fix "weak chins." (AKA, perhaps a focus for unstated outrage to help motivate a slightly-weak podcast)

I was offered a tongue depressor by my childhood dentist to help fix a crooked tooth without orthodontia, so when Nestor's book mentioned one orthodontist suggesting that positioning one's tongue to touch the roof of the mouth would matter, I dismissed that part as probably the weakest in the book. That said, the science overall seems to be evolving, research in breathing and the nose apparently increasing, and Nestor is meticulous in maintaining references, including online. Many might be comfortable with some uncertainty and not dismissing this all as pseudoscience. I commend Nestor's reporting.

I also hope that, if industrial civilization eventually passes, and for now where severe poverty without dentistry exists, people will find again whatever practices better prevented dental caries.

That seems natural and obvious?

But unless you have a secret mucus prevention technique, you'll mouth breathe.

I was born with a deviated septum and for the first 15 years of my life I just assumed breathing through one’s mouth was normal and the nose was just for smelling things. After surgery I started breathing through my nose without conscious thought for the first time.

Same but my septum was deviated by a punch to the face when I was 12. I had the surgery when I was 28 and the pleasantness of my breath, jaw tension, sleep quality, and resting heart rate all improved significantly

Yes, certainly for heavy congestion. However, for marginal cases, there might be some body adaptation made to help with efforts at nose breathing. .. Nestor avoids giving specific recommendations, given individual variations and needs. But the research seems to point to: there is a lot going on. For example, apparently the nose contains erectile tissue, perhaps helping explain how one can cycle between now one nostril being easier to breathe through, later the other. .. My very limited experience, living where I would usually call myself "always congested," is that given a little effort/intent at nose breathing, I now sense that my congestion is consistently less than before. (But N<1 as evidence, since there could be some seasonal change as well.)

Both beets and sugar cane are old world plants, and maize-based corn syrup wasn't used as a sweetener until the 20th century. It's true that refined sugar is terrible for dental health, but it didn't come from the americas.

It wasn’t known that beets could be exploited for sugar until the 16th century. Sugar cane was not known in Europe (outside Muslim-ruled areas of Spain) until post-Colombian times. In antiquity, the sole common means of sweetening food in Europe was honey, and later dulce de leche.

Or extracts from sweet fruit like this:

https://en.wikipedia.org/wiki/Powidl

Or, something more Roman, lead! https://en.wikipedia.org/wiki/Lead(II)_acetate

Getting kind of off-topic here, but my recollection is that teeth in the pre-industrial age were often destroyed over time by grit from flour milling that would wear down teeth.

There was a Han Dynasty (200 BC - 200 AD) ritual involving feeding mush to 70-year-olds. (Why mush? Because at that age you've probably lost your teeth.)

However, I have the impression that this is basically as true today as it was then.

It was also an issue of the speed of capture. Paintings and old Cameras had long exposure times so you needed a pose that you could hold for a long time.

https://time.com/4568032/smile-serious-old-photos/

Used to be that you checked cattle's teeth for problems before buying - that's why it's impolite to "look a gift horse in the mouth".

Also done with slaves, from what I've read. Nowadays it's voluntary, sort of.

You don't have to open your mouth or show your teeth when you smile.

This reminds me of some articles showing smiling Victorians, like this one: [1]

Seeing them helps counter the general impression we get from seeing so many dour-faced Victorians from photographs of that era.

[1] - https://www.thevintagenews.com/2018/11/24/smiling-victorians...

Athena Glaukopis

Well, it's complicated. Glaukopis could also be translated as "blue eyed", or "grey eyed", not just "owl eyed".

Being the goddess of wisdom and handicraft (among other things), perception was a crucial attribute. Having big eyes (like the owl) could be interpreted as having good visual perception.

But it's not just about the size. She's also described as having "bright eyes", or "flashing eyes", or "darting eyes". It's more about the acuity of perception, than about some emotional aspect.

Fascinating insight. It is little gems such as these, that make HN a cut above the rest.

Pity it's not true.

Please elaborate

Actually it's the OP who should probably provide some proof for the claim.

>In Middle Ages, someone smiling a lot would be perceived as stupid.

Unfortunately 20th-century photo magazines, TV, and later Instagram and selfies changed that...

Why would that be unfortunate? Isn't smiling a good thing?

No, it indicates being an idiot (and/or a fake). The old ones had it right.

No they didn't.

I mean, life was objectively a lot worse in the Middle Ages. Give a person from that era a McMansion and tell them to expect clean water, a hamburger, and a soft modern bed every night, they’ll smile too.