The way you get plague is from bacteria that you become infected with after being bitten by fleas that are host specific to rats. Think that through in those cascading levels of filth. You would have to be pretty much catatonic to not notice how disgusting you were.
How did they breed? They had fleas...lice, crabs, VD....Jesus! They were like human lab cultures. They never bathed. They must have smelled. Their houses were heated by like coal smoke and thatched with moldy straw. Can you imagine what the dating scene was like? They didn't have bathrooms. They didn't know about that whole spectrum of human existence. There was like a lapse of reason where they forgot showers existed for a thousand years.
I wonder if there was some environmental impetus, like something creating mass hysteria. That was a theory behind the Salem 'witches' - that they had fallen under the affect of some kind of hallucinogenic botanical or bread mold and were naturally assumed to be possessed by demons. Ergot.
There's another pretty vacant lot - the 'Pilgrims'. They were too right-off-the-boat weird to even get credit as being part of American history. That is European history, specifically that which portrays the segue from the smothering pestilence of that-era England into the evolutionary blast-off of Colonial America...like a gilded door swinging open and letting in the sunshine of enlightenment; a truly seminal moment.
Get this. There were rats on the wooden ships that the Pilgrims came over on. It's like they packed the filth with them. They had like boom cranes on the wharf lowering cargo nets full of rats and disease into the holds of those ships. I don't even want to guess about the bathroom situation. It took them like six months to cross the Atlantic. Half of them died of some disease enroute and were then cannibalized by their fellow voyagers. Quite a gamble I'd say.
White people should be allowed to give spectral evidence again in trials today. It was a forensic technique precedent to like DNA and so forth.