"That doctors washing their hands..."

That doctors washing their hands after going to the toilet increases survival rates significantly during surgical procedures.

nbfox3137

"We are going back..."

Glass. Some cultures have had glassware for a long time while others developed without it. Japan and China are great examples of not having it and it impacts their architecture design as they did not have glass pane windows. China also has had arguably some of the best ceramics artisans because of the need for stone wear where glass cups would have worked.

We are going back a couple hundred years here but that's still fairly recent in terms of mankind's history.

666pool

"Two years ago..."

Two years ago scientists learned that tongues can smell. They can detect some odors as part of the tasting process.

Cattlenfell

"Scientists knew that nutrition deficiencies..."

All vitamins were discovered between 1913 and 1948.

Scientists knew that nutrition deficiencies were causing diseases, but couldn't figure out what was deficient. They fed mice highly purified food, but the mice failed to thrive until milk was added, leading to the theory that there was some life-sustaining, but unidentified, component in milk that was not present in the other food. That led to decades of speculation and research until the first vitamin (A) was discovered in 1913.

Enreni37001

"There's a reason..."

How to tell if someone is dead.

There's a reason people used to keep family members who they thought had passed in their home for weeks before burying them.

Ms_khal2

But the smell!

What about the smell?

This is how you know my modern sensibilities would doom me if I happened to be a time traveler and got stuck in the past.

"The earliest cutlery..."

Cutlery that doesn't make the food taste awful, and isn't ridiculously expensive.

Gold and silver cutlery were useful to the rich (besides being a display of wealth) because they could eat without affecting the taste of the food. Copper, brass, tin etc. all really strongly affect the flavour of the food.

The earliest cutlery is some 4,000 years old, but for most of that time, very few people used it; instead they'd eat with their hands.

Stainless steel was only invented in the 1800s, and its high resistance to acid and no discernible taste made it suitable for cutlery.

Ishmael128

"That hitting kids..."

That hitting kids is bad, and does not enforce positive behavior. Some knew this instinctively, but mostly, nope.

pearlescence

"There simply isn't..."

A scientific understanding of what culture is and how it works.

Before the 1800s or so, people just assumed their culture was the one, single, objectively real and correct way to live, therefore all other cultures were objectively wrong and the people weren't really human.

It was common for anthropologists to encounter remote societies that insisted "The people in the next valley are monsters, they are not human" - and if you went into that valley, they'd say the same thing about the people you were just talking to.

That made it pretty easy for actual social scientists to grasp how cultures define reality, but even now the average person has very little social science education and people tend to still believe their cultural norms are 100% real, natural, and objectively correct - i.e., look at how angry people get when you explain that gender isn't biological, it's cultural.

Or ask a white midwestern American if rap is "real music." The idea that cultures other than your own aren't "real" is an incredibly ignorant, unscientific understanding of the world, but it was really only recently that we came to understand it, so there are still a lot of people out there who will say "Oh, [those people] don't have culture," or "[Those people's music] isn't real music," or art or slang or whatever.

There simply isn't such a thing as humans that lack culture - all humans have culture, all culture is real.

AdSquare3953

"People commonly think..."

How dogs drink water. People commonly think dogs make their tongue into a spoon to lap it up but the tongue curls backward.

inkseep1

I took care of a friend's dog very recently...

...and now I'm poring over the image in my head of her lapping at the water in her bowl. It's so cool.

"Pretty much everything used in statistics..."

Loads of math that gets used all the time. Pretty much everything used in statistics wasn't known until the 20th century. We had a good grasp of probability theory and a few distributions, but not many statistical tests as we know them today. The idea of a null hypothesis as it is used today wasn't codified until 1935.

Same goes for a lot of linear algebra, computers kinda made linear algebra really important, so people are still discovering heaps of useful things about it today.

Cytokine_storm

Now that we've gone through all of these examples,

I can't help but think of others, such as the fact that the chocolate chip cookie wasn't invented until the 1930s, and that pockets in clothing didn't become a thing until roughly 500 years ago. I know, right?

Got some of your own observations to share? Feel free to sound off in the comments below!