Zombie folklore originated in Afro-Caribbean voodoo. Haitian witch-doctors called bokors injected unsuspecting victims with "Zombie Powder" which supposedly contained, among other ingredients, the poisonous toxins of puffer fish and the skin of tree frogs. When introduced in the bloodstream it caused body functions to slow to a death-like halt. The infected would be pronounced dead by unassuming doctors, and buried alive in a coma. A few nights later, the bokors would sneak to the graveyard, and dig up the bodies. And either from the powder or lack of oxygen in their coffin, the victims would now be brain-damaged and under the control of the bokor.
The first film to feature zombies was 1932's White Zombie, which took a lot of concepts from Haitian superstition. Bela Lugosi played the bokor who secretly drugged his victims and put them into slavery. These victims were not the human-hungry zombies that we are used to, though. Instead, they were the more realistic Haitian zombies thought to be dead, but now living in a comatose state. It would take a few decades before Hollywood created the supernatural zombies we know today.
Beginning in 1968 with Night of the Living Dead, George A. Romero's Dead series set the rules for what a Hollywood zombie should be: slow moving, rotting, and craving the flesh of the living. His movies also popularized the idea of reanimation being contagious; those bitten by zombies turn to zombies themselves (a concept most likely taken from werewolf folklore). This leads to humans being outnumbered by their undead counterparts, forcing them to find shelter and protection from the onslaught.
Another Romero trademark is a sprinkling of social commentary within the flesh eating. The original Night played with racism by having an African-American lead stuck in a farmhouse with a group of white folks, leading to a terrifically jarring final scene. The zombies in Dawn of the Dead (1978) instinctively flocked to the shopping mall, a clever dig at mindless consumerism. And in Romero's latest Land of the Dead (2004), class separation was represented by a fortress exclusively for the rich, protecting them from zombies and the living poor. Audiences love the mix of gore and critiques on society so much that the Dead series continues today, with Diary of the Dead being Romero's next installment.
Foreign filmmakers picked up Romero's baton and interpreted his vision of zombies into their own twisted ways. Most notable was Lucio Fulci's Zombi series. Titled to capitalize on the success of Dawn of the Dead, which was called Zombi in Italy, Zombi 2 was more violent and gory than any of its American counterparts. Fulci relished in creating decaying, maggot-infested zombies while Romero only coated his ghouls in purple face-paint. The Italians were also obsessed with gruesome death scenes, and each Zombi film has a cringe-worthy eye gouging scene. Other acclaimed (and bloody) zombie flicks from overseas are 28 Days Later (England, 2003), Delamorte Delamore (Italy, 1994) and Dead Alive (New Zealand, 1992).
Some good U.S. made movies are the Evil Dead trilogy (plus Army of Darkness) and the darkly comic Return of the Living Dead series. There are also many other terrible D-movies that are fun to watch such as Redneck Zombies (1986), Children Shouldn't Play with Dead Things (1972), and Chopper Chicks in Zombietown (1989). In recent years, there has been the parody/homage Shaun of the Dead (2004) was a recent hit, and the remake to Dawn of the Dead (2004) was both critically and commercially acclaimed.
We are fascinated by zombies because they straddle the line between life and death. These walking, rotting corpses should be under the ground but for some reason they wander the Earth, looking for their next meal. The truly terrifying aspect is that they show what could become of us after we pass on: uncontrollable, soulless creatures with no remnants of who we used to be.