Look back through our history, and you’ll find that the idea of fake news definitely isn’t new. In fact, there’s a ton of theories, stories, and scientific “facts” that we now know just aren’t true. Making matters worse, some of those facts weren’t simply accepted as truth, but were used as the very building blocks of the world we know today…for better or worse. Usually worse.

Drive across the US today, and it’s no big deal. There’s highways and rest stops as far as the eye can see, but just imagine what it must have been like a few centuries ago. Vast herds of buffalo, flocks of thousands of birds, dense forests… paradise on earth? Absolutely, until mankind came along and ruined the heck out of it.

What New World settlers found was so incredible that they developed what the British Association for American Studies calls the “myth of superabundance”: a belief that this unsettled world was limitless, and that there were so many resources that there was no reason to think we’d ever use them all up. We began making decisions based on that principle right from the moment we set foot on the East Coast, when we decimated beaver, elk, lynx, and bear populations, and completely wiped out the passenger pigeon.

Obviously the myth of superabundance couldn’t be less true. And spoiler alert: we used everything up. Even as the promise of wealth and limitless natural resources drove people west, the National Park Service says that loggers destroyed entire forests, bison were hunted from a population of around 60 million down to about a thousand, elk and beaver were poached relentlessly, and herds of livestock destroyed wild grasslands. Preservationists fought against those practices, and they had an uphill battle. Fortunately, they persevered — somewhat — and it’s why we have national parks and protected areas today.

We thought we could read a person’s character by their appearance, and it’s made us superficial jerks

We do it all the time, whether we know it or not. It’s the reason actors like Jason Statham have a job always playing the same type of character — because we think we know what kind of person he is by the way he looks. That’s the basic idea of physiognomy. The Iris, the official blog of the Getty Arts Foundation, says that physiognomy has its roots in the ancient world. Pythagoras was known for rejecting students if they didn’t look smart, and Aristotle wrote that people with broad faces were dumb… making even ancient brainiacs superficial jerks.

It wasn’t until Giambattista della Porta’s 17th century writings that the concepts of physiognomy were concretely defined, and it’s still why we call people “low-brow” or “stuck-up.” A Wired article says the scientific community largely called the whole thing bunk by the end of the 1600s. But that didn’t stop physiognomy from lingering on in various dangerous forms for a few more centuries.

According to that same Wired article, it was Cesare Lombroso who really did some serious, stupid damage. He was a criminologist writing in the 19th century, and he firmly believed that the world’s criminal element could be identified at a glance. How? By their ape-like appearance, their vestigial tails (you read that right), and their tattoos. So thanks, Mr. Lombroso, for reinforcing the horrible idea that you can and should totally judge a person based on appearance.

We thought smells made you sick, so we cleaned up the wrong things

You wouldn’t want to have lived in 19th century London. In the 1830s, epidemics of typhoid, influenza, and particularly cholera decimated the city. According to London’s Science Museum, it was so bad that even the upper class started to sit up and take notice of the squalor that the city’s poor were living in. Behind it all was the miasma theory of disease transmission, which basically meant that it was the bad-smelling air that was making people sick and dead. That was completely wrong, of course. But this misunderstanding actually had an incredibly positive impact on the world as a whole.

The miasma theory led London to make improvements in sanitation, drainage, and ventilation, and that’s important stuff for a civilized society. It didn’t happen overnight — 1858 was the year of the Great Stink, and we’ll leave that to your imagination — but there was still a problem. After the cleanup, people wouldn’t accept that bad smells didn’t make you sick.

In the 1850s, an anaesthetist named John Snow theorized that the cholera that killed so many citizens wasn’t a stink, but actually a water-borne contagion. But the miasma theory was so widely accepted that no one believed him. He died in 1858, and people were still stamping their feet and firmly insisting that it was the air.

The miasma theory hung in there until 1892, and according to Buckinghamshire Chilterns University College lecturer Stephen Halliday, it wasn’t until a cholera outbreak in Hamburg, Germany, didn’t spread to London — in spite of London’s still-somewhat stinky air — that people started thinking that maybe Snow had been onto something after all.

We believed in a magical, Christian kingdom, so European conquerors ran amok in Asia and Africa.

In 1145, rumors of a mysterious Christian kingdom started circulating through Europe, and you would totally want to live there, too. According to ThoughtCo., the legend said that the kingdom was ruled by the good Christian king Prester John. There was no crime and no vice, there was plenty of food, the rivers flowed with gold, and it was the site of the Fountain of Youth. Global Middle Ages says it was called the richest kingdom in the world, filled with jewels, natural resources, and spices.

There was a problem in paradise, though: the kingdom was surrounded by all kinds of heathens and savages who wanted nothing more to plunder it… which was, presumably, not at all why Europeans had set their sights on paradise.

No one was exactly sure where Prester John’s kingdom was, and there were plenty of expeditions sent to find it. One of the early ones was dispatched by Pope Alexander III, who hoped to defend the kingdom against the infidels. Later expeditions mapped huge patches of Asia and India in hopes of stumbling across the beleaguered king.

When explorers determined that the kingdom wasn’t in Asia, they set their sights on Africa. According to Black Past, the legend of Prester John was the driving force behind Italy and Portugal’s 15th century forays into Ethiopia and opening Africa to European exploration. We don’t really need to discuss the consequences of how Europe’s trips through Africa turned out, since society continues to deal with their repercussions every day.