Origin Story: A Big History of Everything

by David Christian

But population growth was never steady. Everywhere, it was interrupted by catastrophes. Disease, famine, war, and death—the Four Horsemen of the Apocalypse—flourished in the agrarian era. As mentioned earlier, unlike nomadic camps, villages accumulated waste and attracted vermin, so diseases spread fast. Where new diseases appeared—infections for which people had no immunity, such as smallpox—it was not uncommon for half the population to die. Farmers were also more vulnerable to famine than foragers were, because they relied on so few crops. When food began to run out, weeds, acorns, and tree bark could support people only for so long, and the very young and very old suffered most and died first. As populations grew, villages fought over land, water, and other resources. Their battles summoned the Third Horseman, war, who could be even more ruinous than disease and famine and often worked alongside them. Humans had always fought, but in farming societies more people were involved, and weapons became more lethal as fighters acquired metal spears, chariots, and siege engines. The Fourth Horseman, death, rode behind the other three.