A month ago, I was walking through central London -- along Shaftsbury Avenue -- when suddenly I found myself surrounded by the massed ranks of the Undead. Hundreds of limping blood-flecked zombies were stumbling through the streets, staring into the middle distance, groaning: "Brains. Brains. Feed me brains."

In the year 2010, this stinking creature has risen with a groan and a shriek from our collective subconscious. From Brisbane to Chicago to Rome, there has been a surge of "zombie walks" -- flashmobs of up to 8,000 people at a time dressed as zombies like this, begging for flesh. They dominate the cinema screens, with more than 50 zombie flicks released. They are best-selling video games like the "Left 4 Dead" series. They are the stars of the top-rated US TV show The Walking Dead. They have limped up the bestseller lists, with mash-up classics like Pride and Prejudice and Zombies. (Opening line: "It is a truth universally acknowledged that a zombie in possession of brains must be in want of more brains.")

Indeed, the city of Minneapolis just agreed to pay $160,000 in compensation for a group of zombies who were prevented from marching -- a great blow for zombie rights, marking the end of their comeback year.

Why now? Why would a global recession be matched with the global procession of zombies? Obviously humans have always sought the rush of a scary story -- but I do think if you look at the monsters a culture summons from the dark and from its own imagination at any given time, you can learn something about its subtler anxieties. So buy me a one-way ticket to Pseud's Corner: I want to talk about the sociology of the Undead, baby.

The idea of these mutants has been mutating for a long time. The notion of dead people who rise again and hunger for human flesh is found as long ago as the Epic of Gilgamesh, originating in 2500 B.C. But we get the word "zombie" from Haiti, where the local voodoo religion says sorcerers can raise the dead and turn them into a slave army. (There is still a law on the Haitian statute books banning zombie outbreaks.) The first Hollywood movies about zombies, from the 1930s, stuck to this idea of them as doing the bidding of a dark magician.

The modern zombie was only born in 1968, and its father is George A. Romero, who wrote and directed the masterpiece Night of the Living Dead that year. He stripped away the magician controller. His zombies are simply mindless hunks of rotting flesh, shuffling towards food, infecting anyone they bite. It's in his films that we find the best clues to why the zombie came back now.

In his best -- Dawn of the Dead, made in 1978 -- a few surviving human beings hole up in a shopping mall in Middle America, only to find the zombies have gravitated there and are ambling endlessly through the aisles, soothed by the muzak and the artificial lighting. "They have come here out of some instinctive sense memory. This was an important place for them," a startled onlooker says. The humans refuse to leave, even as the sanest person among them snaps: "You're hypnotized by this place. It's so bright and neatly wrapped -- do you not see that it's a prison too?" Later, she stares at the Mall-mulling zombies and says: "What the hell are they?" A man replies: "They're us. That's all."

That's the niggling fear that is always taken and caricatured by the zombie genre. They stumble through life aimless, affectless, shaping nothing, understanding nothing, with no control over their lives, thinking only of the next bite, and the next. Who hasn't felt like that for at least some of 2010? As disaster occurs all around us -- economic, ecological, political -- who hasn't felt that their own little life of shopping and eating and consuming isn't a little zombie-like? The zombie is the amoral consumer made of (dead) flesh. Have we started to see zombies all around us because -- on some distant, allegorical, semi-serious level -- we fear we have become more like zombies ourselves?

This anxiety is best explored in the mega-hit movie Zombieland. It is about a cowardly Californian called Columbus, played by Jesse Eisenberg, who lives a cosseted closed-down life in his air-conditioned apartment, playing video-games, masturbating, and obsessing over the risk from germs. Then the zombie apocalypse happens -- and he discovers all the primal instincts that had been buried beneath the disinfectant. In fighting back against the Undead, he realizes he too was stumbling aimlessly from bite to bite, with no rationality and no greater purpose. He was only slightly less dead than them. He says: "A zombie isn't a dead person who's come back to life. It's someone who's been infected with the plague of the twenty-first century."

Who doesn't have a niggling sense that the 21st-century life pushed on us endlessly by advertising -- of endless shopping as an end in itself -- bears as much relationship to a full life as Muzak does to music? Of course some consumption is a pleasure and a joy -- the inhabitants of Zombieland certainly miss the supermarkets when they are gone. But it has eaten too deeply into our brains. Listen to any ten year old convinced they are worthless if they don't have the right brand of trainers from the shiniest shopping center: They are sensitive antennae picking up the dysfunctional priorities of our culture. Then watch again the zombies limping through Dawn of the Dead's mall, grasping for more.

In some ways, the zombie genre is a despairing fiction for despairing times. Any moment of relief, or happiness, is fleeting: you know that ultimately the quest for a safe space, far from the infection, will fail, and everyone will devolve to the level of the zombie. Intriguingly, scientists at the University of Ottawa and Carleton University carried out computer modeling of how a zombie outbreak would proceed, and found that this is true: We would have no chance.

But zombie stories also ask a different, more hopeful question (as the Undead munch on a human ribcage): How do you stay human, in an environment that so often dulls and deadens your humanity? There is almost always only one answer: Turn away from worrying about consuming and acquiring (and the panic that you can't afford to do it anymore), and look to the humans around you. The genre shows we need a common cause and fulfilling relationships much more than we need another iPhone app and another milkshake -- but it can take a crisis to make us realize it. At the climax of Shaun of the Dead, the central character announces: "As Bertrand Russell said, 'The only thing that will redeem mankind is cooperation.' I think we can all appreciate the relevance of that now."

As the zombies surrounded me on Shaftsbury Avenue and let out their low groan, I thought -- yes, I know why you rose from the grave now, in the long, bleak year of 2010. Now, if you'll excuse me -- brains. Brains. I need brains...

Johann Hari is a writer for the Independent. To read more of his articles, click here or here. You can email him at j.hari [at] independent.co.uk

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