In the midst of the coronavirus outbreak, this idea of a body as an assembly of species—a community—seems newly relevant and unsettling. How are we supposed to protect ourselves, if we are so porous? Are pandemics inevitable, when living things are bound so tightly together in a dense, planetary sphere?

The history of civilization has hinged on the building and demolition of boundaries between species. Early agriculture disregarded most of the natural world in order to cultivate only the most productive plants and animals; this allowed populations to grow and cities to flourish. But crops and livestock, once they were concentrated in one place and cultivated in monocultures, became vulnerable to disease. As cities and farm operations grew, people and animals crowded closer together. The result was a new epidemiological order, in which zoonotic diseases—ones that could jump from animal to human—thrived.

At first, these diseases remained confined to the places where they originated. Then globalization arrived. John McNeill, an environmental historian at Georgetown University, speculates that the first wave of the cholera outbreak of 1832-33 was the first true pandemic; it reached every inhabited continent by hitching rides on caravans and ships. More infections followed, often affecting the crops on which people depended for food. In the early nineteenth century, potato plants in South America suffered from a blight; the culprit, a mold called Phytophthora infestans, sailed to Ireland in 1845, where it led to a million deaths. In the eighteen-sixties, a tiny aphid-like bug called phylloxera migrated from the United States to Europe, nearly pulping the French wine industry; in the nineteen-sixties, Panama disease eradicated the world’s favorite commercial banana, the Gros Michel. In 1970, the fungus Bipolaris maydis decimated the American Corn Belt before spreading worldwide; another fungal infection, wheat rust, has caused countless famines worldwide.

And yet the upsides of industrial agriculture were hard to resist. In the nineteen-fifties, the Green Revolution churned out so many cereal crops that the United States began giving food away; when its techniques were exported to the rest of the world, they defused the “population bomb.” In the sixties, the American-led Livestock Revolution vertically integrated the production of animal products, creating a parallel increase in the consumption of meat. By the seventies, big poultry companies were churning out so many chickens that they had to invent new products—chicken nuggets, chicken salad, chicken-based pet food. Large corporations bought up local producers of poultry, pork, and beef; feedlots grew to the size of fairgrounds; hen houses dwarfed neighborhood strip malls. Farms went from being small operations with an average of seventy chickens to factories housing thirty thousand birds. In the eighties, with the Blue Revolution, the industrial farming of fish expanded, too. From 1980 to 2018, the global production of animals for consumption grew about one and a half times faster than the world population.