The Great Mental Models, Volume 2: Physics, Chemistry and Biology

by Shane Parrish

The precise origins of the Black Death are unlikely to ever be known, but we do know how it spread. Animals, in particular rats, carried fleas infected with the plague bacteria when they climbed aboard ships sailing around the world. The fleas then jumped onto humans, bit them, and infected them with the Black Death. In the 1340s, the trading routes that were bringing Europe new wealth and opportunities brought it something more sinister. With no knowledge of what was causing this devastating disease, people continued to move and trade, spreading the plague further and further afield. As time progressed and more and more people died, society began to change. Old systems of labor collapsed with so few people left to work. Workers could demand more money because they were less replaceable. As wages rose, rents fell as landlords realized, to their chagrin, that they possessed more land than there was demand for. Survivors were considerably better off, and increased social mobility enabled even the poorest people to rise in society and earn more money. New industries bloomed to meet their needs, as those who once struggled to survive now had disposable income. Land became cheap and labor became expensive. With fewer workers, people developed labor-saving technology to make farming more efficient. The overall effect was a restructuring of society to be more equal. While the Christian church had long dominated society, the Black Death weakened its grip for two reasons: people fo...