Josh Valcarcel/WIRED

Ten thousand years ago in what is now eastern Turkey, humans were settling into villages and starting to produce what humans produce best: garbage. Wild boar, omnivorous and not above scavenging, found this convenient. So the gutsiest among them stuck around the trash heaps even when people were about. Humans killed the most aggressive pigs, leaving the tamest to breed amongst themselves—and thus the domesticated pig was born.

But this would become a human-livestock relationship like no other, argues historian Mark Essig, whose book exploring humanity’s long relationship with swine, Lesser Beasts, is out today. While cows have always been out at pasture, pigs have historically lived right among people, roaming cities and earning themselves an often unpleasant reputation. They've become more than just a source of food: They're a cultural force, a tool religions and cultures use to solidify their own identity—or attack their enemies.

At the very heart of it all is the fact that pigs eat poo. Good for them! Quite frankly, that’s a solid evolutionary move: They won't find much competition for the stuff. It’s a bad idea, though, if you’re looking to make friends among humans. In the Near East, an area not exactly known for its expansive forests (the pig's ancestors were used to roaming among trees digging up tubers and hoovering up acorns), early domesticated swine kept to the cities, eating feces and garbage and the occasional human corpse.

Interestingly, their traditional diet is probably why pigs are so damn smart: They can figure out how mirrors work and use them to search for food—oh, and they can play videogames. Being a grazer like a cow requires very little brain power, but being an omnivore requires real smarts to secure your next meal.

So, according to Essig, the pig's bad habits led certain Near East cultures and religions, including Judaism, to brand it as a pariah. But then the Romans came along—and the Romans really, really liked pork. Essig attributes this to differences in religions and geography. “The Near Eastern religions tend to be focused on purity in a complex theological way that just wasn’t true of the Romans,” he says. “But the other bare fact is that with the Romans, the Italian peninsula is much wetter, so you have oak forests where the pigs can graze.” The Romans let pigs continue this foraging way of life in forests around their great city, then shipped them in to eat. Because pigs weren't wallowing in the streets, the Romans didn't brand them as unclean.

Medieval Europeans would try and execute pigs that killed or injured humans. Courtesy Basic Books

These were the beginnings of using the pig as a cultural pawn against Jews. “The contrast with Rome is striking, just because you get these puzzled expressions whenever Romans came in contact with Jews,” Essig says. “They would make sort of jokes about it because they just couldn't understand why the Jews would give up such an incredibly useful creature.” You can, after all, use higher percentage of a pig's flesh than a goat or cow, plus pigs churn out more offspring and get to slaughter age quicker.

Early Christians followed the same dietary laws as the Jews, but the arrival of the New Testament and its new rules changed all that. Now free to eat pork, Christians came to define themselves by it, and this fueled nasty and absurd antisemitism, known as blood libel. Essig writes: “Some Christians asserted that Jews, denied the meat of the pig, lusted after its closest equivalent: human flesh.” Children in particular were supposedly in perpetual danger of being killed, salted, and eaten by Jews, who would use their blood to make matzo or magic potions.

In reality, children should have been more worried about the pigs themselves. Medieval Europe had a serious problem with roving bands of swine chewing off the ears and noses of kids, at times even killing them. But the offenders weren’t just slaughtered: No joke, they were put on trial. One pig in 15th-century France got into a house and killed a boy by eating his face and neck. The swine was first jailed, then tried and convicted and finally hanged.

The problem comes back to the fact that pigs are just fundamentally different from other farm animals like sheep or cows. Those are herbivores, and must be put out to pasture. Pigs, on the other hand, lived right among Europeans—in the streets or beside their homes eating trash. “And so it added to the uncanniness of having the pigs around,” Essig says. “Here are these creatures that eat what we eat, they live amongst us and yet they might turn around and kill and devour us.”

But the relative freedom of pigs would not last. As the West industrialized, so too did its pig industry. In Europe, distilleries kept pigs to chow down on the grain byproducts. Breeders crossed the typically leaner European variety of pig with the enormous Chinese variety, which was better suited for the cooped-up sty lifestyle, to create the breed of pig you see today. In America, the horrors of massive-scale pig farming came to Chicago, which Upton Sinclair made famous in his exposé The Jungle (which was actually a novel as opposed to a piece of traditional journalism—but it did the trick to stir up outrage).

Europe once had a serious problem with pigs, which often roamed the streets unsupervised. Courtesy Basic Books

Today, industrial pig farming is a calculated, often brutal affair, churning out the most meat in the least time with little regard for the welfare of the swine. Among the “litany of horrors” they endure, Essig writes, pigs spend their lives standing on slatted floors over septic pits “and ventilation systems are often used sparingly to keep heating and electricity costs down.” They’ve been known to gnaw each other’s tails off, and sows are kept in cages only a bit bigger than themselves to keep them from rolling over their piglets and crushing the things to death.

All is not unwell, though. While the US lags behind in legislating welfare for farm pigs, the European Union now requires that pigs get access to areas with solid floors, not just ones with slats. The best hope for change here in the US, Essig argues, is for consumers to pressure producers of pork for change. Americans may be a bunch that’s been historically wary of regulation, but when corporations start fearing they’re losing business, they start listening.

Really, all pigs ever wanted was a little garbage. And yeah, they've eaten a few kids, but humans have eaten far more of them. They're crazy-smart, crazy-resourceful, and not at all deserving of the way humanity portrays them. Pigs may eat shit, sure, but that doesn't mean people should treat them like it.