What plagues have ended or vastly altered civilizations

As others have mentioned, most of the population of the Americas was settled farming population, not nomadic. But when considering whether population reduction could affect culture, you’re forgetting “hell is other people.” Smaller populations find themselves at the dubious mercy of more numerous neighbors and get exterminated, enslaved, forced to learn the language of their conquerors, and/or (most commonly of all), displaced onto marginal land, where the struggle to survive often results in loss of the sort of things leisure time previously made possible.

To expand on Dr Drake’s “people willing to ask tough questions” point, constituted authority in the Middle Ages (the Church and the feudal hierarchy) lost a lot of clout due to the Black Death. The death was so widespread and so indiscriminate that everyone could see that it wasn’t just sinners or people of low birth dying; a repeated theme in writing of the time is that both the mighty and the weak suffered. People began to question the natural superiority of the nobility as well as the moral authority of the church. The fact that some nobles and some cloistered churchmen did survive by taking ruthless quarantine measures (some Italian leaders had homes with plague victims sealed and set on fire, if I correctly remember my Tuchman) helped further weaken the belief that the nobles and the church were the protectors of the common people.

Idi Amin named a military order after the Mosquito because of its role in foiling European colonization of Uganda.

I recently read 1491. A striking point was that a hepatitis outbreak killed large numbers of East Coast Indians just before the Mayflower arrived, setting up the conditions allowing the first European colony to successfully establish itself in New England.

For what it’s worth, medieval historian/populist Mike Loades has demonstrated how Europeans made soap and washed clothes on his pop documentary Going Medieval.

Someone with OCD didn’t know about fleas being more than a bother, any more than others did, nor did he have more access to insecticide than others did.

If you don’t get what I meant by the phrase I’ve now repeated 3 times, that’s fine. It’s not like I’m going to win a prize.

It’s not unusual for the cultural “library” of preliterate societies to reside in the memories of just a few of its members. Everyone knows who to go to, for instance, for creation myths and special prayers. When these repositories die, so can the culture.

I read once that the abandonment of the Khmer capital of Angkor Wat may have been the result of malaria. The buildings were surrounded by vast pools of water, which bred mosquitos. The people left, and the place was unknown for about 400 years.
The civilization responsible for the Tiwanaku ruins (in Bolivia) disappeared-whether this was due to drought or disease is unknown.

Is there any evidence OCD is a heritable trait or learned behavior, or is it just a garden-variety bit of mental illness that crops up at random?

I think this plague/OCD connection is stretching a point so thin that you can’t see it.

It may well be. It’s just a pet theory of mine which is why I’m not wasting much time on it. I do think there is evidence for it but I’m not exactly looking to get published or anything.

Ten people own ten houses full of furniture and cool stuff. Five of them die. Now five people each own two houses full of furniture and cool stuff.

That’s an increase in per capita wealth, not absolute wealth.

I once read a fascinating book on how smallpox destroyed native populations: Pox Americana, but Elizabeth Fenn.

You’re right; I said that exactly backwards. Thanks for the correction.

And you could argue that the Irish Potato Famine had a large impact on the US as well, because of the large numbers of Irish people who, faced with starvation and little economic opportunity, saw emigration as the best solution. NYC and Boston might be very different places today had the Irish not come in great numbers, and there would be differences elsewhere as well, since “generic white Americans” would not have assimilated so many Irish into their fold in the 20th century. Maybe we would not celebrate St. Patrick’s day or Halloween today had they not come.

I can’t parse this sentence and have it make sense. What did you mean?

According to Panatti’s Extraordinary Endings Of Practically Everything And Everybody, before the Plague Of Justinian Roman scientists and especially doctors were making great discoveries. They may have even been closing in on germ theory. Then, the Plague came. The scientists could do nothing to prevent or cure it. Sick and dying, the people ran to the church for spiritual comfort. The Catholic church grew in authority. All the learning of Rome was lost.

Likely (cause I can’t find my copy at the moment) I’m misrepresenting Panatti. But the impression I got was that without the Plague Of Justinian, history would be vastly different and science would be a thousand years ahead.

I’m going on a vaguely remembered explanation of the period just after the Romans stopped being a force in Briatain (400AD roughly?) The Celtic kingdoms had been converted by someone who was a proponent of one of the non-orthodox Christianities of the time (Manicheanism?). The Angles and Saxons were proper mainstream Christians. When push came to shove, the celtic forces collapsed since their entire population had been cut in half by climate failure and a plague. This apparently spared Britain a much more bloody and vicious tribal and religious war.

The problem with population collapse is just that - the population collapses. Some workers and their specialties disappear entirely. The market size to maintain the specialty trades may disappear, along with the closely guarded trade secrets. You maybe no longer can get the ornate dishes, or fancy wall tiles that decorate the old buildings. Demand is skewed. With more than enough houses to go around, for example, nobody needs a house built for the next decade or two. With fewer men, the slightly better off lord next door may see an opportunity to help himself to your town (or with so many dead, the line of succession may be blurred.). (Conquest was often followed by looting and burning). people abandon lightly populated towns to congregate in bigger ones leaving areas of the country abandoned. Unrest means travel and trade is less safe, since there is not a big enough army left to patrol the whole countryside. And so on… Chaos often follows disruption; and tax revenue is down with a smaller population base, meaning smaller armies, less public works, etc.

One thing I recall was that the lonely cottage deep in the Black Forest, like the setting for Hansel and Gretel among other fairy tales, was due to the expansion of the Black Forest after the bubonic plague. Many smaller villages were mostly abandoned and the forest covered them over within a generation.

This isn’t right. For one thing, the Angles and Saxons were not converted until a couple of centuries after the conquest. The non-orthodox version you’re probably thinking of is Pelagianism, but other than its founder’s being British, there’s really no reason to assume his beliefs were widespread in Britain. For one thing, the British converted a couple of centuries before he was born. There is some evidence of British depopulation around the same time as the Anglo-Saxon arrival, but I’m not aware of evidence to pinpoint the relationship of the two: it might have been just before, consistent with plague, or just after, consistent with death in battle and emigration.

Another good book covering (kind of) the same material is the Lost City of Z, a biography of Col. Percy Harrison Fawcett who was obsessed with finding a highly-populated city in the Amazonian rainforest.

In it, he tells the story of Spanish explorer Francisco de Orellana who (while basically fleeing another failed expedition) was the first European to travel down the Amazon River. His journals, similar to the Mississippi account above, talks about the hundreds of thousands of natives in huge villages he passed during his journey.

Later explorers assumed the journals were just full of lies, repeating his journey they encountered basically nothing except a few scattered tiny villages. Now we have a lot of evidence to show that de Orellana’s estimation of the population along the Amazon was probably very accurate.

Side note: Threads like this are why I keep coming back to the SDMB after 14 years.

Whether the Spanish Influenza epidemic of 1918-19(ish)would fit into this category would be worth exploring. It supposedly killed in excess of 20 million people world wide. My now 95 year old mother was born in 1918 and I remember her mother (yes, my grandmother) telling me about her brothers coming home from the Great War stricken with it as well as my grandfather coming down it. She was looking after a baby and tending to my sick grandfather. I remember her saying he sweat so much that she could literally wring out his suit of underwear.

Yet, as contagious as it was, neither my grandmother, nor my mother got the disease and my grandfather along with my two great uncles made a complete recovery.

As I say, I don’t recall the details.
It may have been one of Daniel Boorstin’s books where he was talking about how the various calendars and feasts (in this case Easter?) were determined. The queen, wife of the local king had one point of view and converted the kindom(s) to her beliefs, and the invaders had a different belief.