We know a great deal about the 14th century plague because paper had been invented and in many places, especially around the Mediterranean, was widely available. People wrote letters and copyists made textbooks, but there was so much paper that men began to keep diaries for their own use. From letters and diaries, and also from sermons that were written down, we know a lot about how culture began to change when the infection subsided.
When all the bodies were buried and grass grew over the graves, the memory of such a surfeit of death remained the controlling principle in people’s life decisions. There were three immediate effects.
The first year after the plague subsided, the birth rate was unusually high, even for the smaller number of surviving women. There are some signs that more twins than usual were born. I’m put in mind of The Shire after Galadriel’s dust has blown out over the lands, when hobbit children were born as twins and with especially curly hair. But there was no magic.
We don’t have proof that there were many twins, unless someone’s PhD research has turned it up by examining birth records. If there were more twins, the explanation may be in our unconscious animal natures. When mice, rats and rabbits are overcrowded, they stop having large litters and some females stop having babies entirely. The animals aren’t calculating survival numbers; their endocrine systems react to signals that we can’t quantify yet. What if something like that was happening? People, as smart as they are, still have animal natures and pick up chemical signals that we can’t yet identify. Maybe the severe loss of life signaled unconsciously for higher fertility.
The other changes were more conscious. Traumatized society turned to or away from religion in more dramatic ways than ever before. Until now, the basic idea had been that monasteries took care of holiness so that the average man could be no more than averagely righteous. This wasn’t good enough now. People began to ask questions about where the soul went after death. Many of the dead hadn’t been properly given last rites or burial prayers. This couldn’t mean they were all in hell, could it? People wanted to find their own holiness. We can find the earliest groping toward what became the Reformation here, as people wondered if it might not be better to read the Bible for themselves. In Italy, some people began to have small home Bible studies.
To the opposite pole, other people ditched religion entirely. It had failed them; its promises were void. What good did fast days and saints’ relics do during the plague? None at all. In fact, they believed that the irreligious sometimes survived better. Heavy drinking and eating may have “balanced the humors” of the body, even if prohibited by religion. Sexual mores followed quickly. The survivors wanted to make up for lost time, and as mentioned before, they may have been responding to hormone signals to replace population.
Writers noticed that young people were behaving shamelessly. Girls dressed with no modesty and stayed out till all hours with young men. They drank and sang, they paid no attention to their family’s reputation. They got married while pregnant (probably with twins).
Another factor here was that modesty no longer made sense. People had seen every body part exposed many times during the plague. What did it matter if cloth covered more or less of the body? Who hadn’t seen a dozen penises on sick people or corpses, and bared breasts in just about any circumstance at home or on the street? Who hadn’t seen legs and arms, once beautiful and sexy, then wasted and covered with flies? Art no longer beautified death; expensive stone effigies began to show gross corpses, not people in robes. Skeletons danced like drunken men across the landscape, urging everyone to eat drink and be merry, then die: ready or not!