A zombie is, in the simplest sense, a living corpse. In cinematic terms, it differs from a vampire in that it doesn't have the same powers (shapeshifting, fangs) or weaknesses (sunlight, holy water, garlic) and usually lacks much brain function. The term "zombie" was introduced into American public consciousness in 1929 as a Haitian Creole world for a corpse reanimated by voodoo; soon thereafter, it was exploited by the motion picture industry in an array of horror films. The form and function of cinematic zombies has shifted throughout the years, but the presence of the zombie film within the horror genre has remained a steady force since the early '30s.
Early movie zombies remained relatively true to the Haitian tradition. The "living dead" tended to be animated by a voodoo spell, and they were usually used as servants to the "master" who raised them. Their appearance was similar to that of the living except that their skin was ashen and their eyes were darkened or occasionally bugged to an extreme size. Typically, they were mute and slow moving, mindlessly following their master's nefarious orders (although at the end of the film, the master often lost control).
1932's White Zombie, starring Bela Lugosi as a villainous voodoo master in charge of a stable of zombies in Haiti, is an archetype for this early style of film. It's generally considered to be the first movie to feature zombies by name, although in 1920's The Cabinet of Dr. Caligari, the title character controlled a sleepwalker, or "somnambulist," named Cesare in much the same way as early movie zombies.
Throughout the '30s and '40s, zombie and voodoo movies spread, with titles like King of the Zombies, Revolt of the Zombies and Revenge of the Zombies being released annually. Several, like Zombies on Broadway and The Ghost Breakers, treated the topic lightheartedly, while others, like I Walked With a Zombie, were highly dramatic.
By the '50s, filmmakers began to play around with established zombie film standards. They experimented with the method of turning people into zombies, for instance. Rather than voodoo, Teenage Zombies featured a mad scientist using nerve gas, while Plan 9 From Outer Space and Invisible Invaders had aliens raise the dead, and in The Last Man on Earth (based on the Richard Matheson book I Am Legend), a virus creates lumbering, zombie-like "vampires." Invisible Invaders and The Last Man on Earth also made zombies more dangerous, relieving them from menial tasks like kidnapping and labor; instead, they became single-minded killing machines, a role that would feed into the next generation of living dead.
The apocalyptic scenario of a planet overrun by murderous zombies in movies like The Last Man on Earth and Invisible Invaders (and, to an extent, the Red Scare-inspired Invasion of the Body Snatchers and the dreamy Carnival of Souls) helped inspire a young filmmaker named George A. Romero. In 1968, Romero released his directorial debut, Night of the Living Dead, which would go on to revolutionize zombie movies as we knew them.
While he borrowed some elements from earlier films, Romero created certain behaviors and rules that would render his living dead the model for zombie films for the next three decades. First, the zombies were driven by an insatiable hunger to eat the living. Second, the zombie attacks were shown in explicit detail, ushering in an era of heightened cinematic gore. Third, zombies could be killed only by damage to the brain. Fourth, zombiism was contagious and could be spread by a bite.
One major difference from early, classic zombie lore was the shift away from voodoo and the concept of a master controlling the living dead. Other elements that weren't necessarily originated by Romero but which became a part of the Romero-esque zombie tradition included: slow, unbalanced movement, an apocalyptic nihilism in which mere survival is a victory and the treatment of zombiism as a plague.
Romero would add to his legacy with several sequels, beginning with 1978's Dawn of the Dead -- which upped the explicit gore ante even more -- and 1985's Day of the Dead. Many increasingly violent and dark zombie movies followed in Romero's footsteps, including a 1990 remake and the offshoot Return of the Living Dead series of films from NOTLD co-writer John A. Russo, plus international entries from Italy (Zombie) and Spain (Tombs of the Blind Dead). Others -- like I Drink Your Blood, Shivers, Rabid and Romero's own The Crazies -- while not containing zombies, utilized the homicidal contagion structure of Romero's works.
In the 21st century, filmmakers have increasingly toyed with zombie movie conventions. Some, like Resident Evil and House of the Dead, have found inspiration in high-octane video game action. Others, like 28 Days Later and I Am Legend, have used contagious diseases that create zombie-like states. Lighthearted films like Shaun of the Dead and Fido, meanwhile, have coined the term "zombie comedy," or "zom com." The 2004 remake of Dawn of the Dead and 28 Days Later have even altered traditional zombie behavior, making them physically quick and agile rather than slow and lumbering. Romero's zombies remain the standard, though, with his Dead series of films continuing into the new century and perhaps even beyond the grave...?