By sheer volume alone, zombies have become popular culture’s dominant monster over the last few decades—of course there is admirable irony that the monster known for overwhelming through volume has also saturated the market. Zombies are everywhere, and though it may seem like the story of surviving amidst zombies would have become cliché long ago, creators still manage to tell some unique stories. Yet prior to 2000, zombie related content was fairly niche, and that was partly because what defined zombie was still far more debatable.
The word zombie, or originally, “zombi” dates back to religion, with original ties to West Africa. During the slave trade, these religions were brought to Caribbean Isles where a new culture adapted. Far off settings in stories often had the appeal of dark and mysterious acts, and Haitian Voodoo became no exception. The voodoo zombie was a recently deceased body raised to serve a master. Voodoo zombies began to appear in literature and plays in the early 20th century, and they eventually made their way into film, with White Zombie (1932), largely considered the first zombie movie ever.
There were some other voodoo zombie movies that followed in the 30s and 40s, but unlike many monsters of the early film era, like Dracula or Frankenstein’s monster, zombies did not have parameters laid out in source material. Their basis in myth allowed for fluidity on the topic, and before going further, I feel a need to distinguish some of the different types of zombies.
Voodoo Zombie: Of note, some of the later rules established that a voodoo zombie could be a living person whose consciousness was slowly taken over, usually with the help of drugs.
Reanimated dead: Bodies brought back to life, usually through science or magic, and who may have violent tendencies, but they aren’t necessarily cannibalistic.
Plague/infected: A virus tends to specifically see those infected becoming violent and hunting for the healthy humans. Some plague movies with mutated people, or those infected with “the rage,” have also quite closely resembled a zombie movie.
Ghoul/Gore Zombie: The term ghoul had a momentary significance in describing the risen dead who craved brains and flesh. Gore zombies/horde zombies were terms sometimes used, but this has essentially become the common cannibalistic zombie we know today. (Technically, had the term ghoul caught on, it would have saved some trouble in distinguishing modern zombies from those in voodoo.)
Back to the movies, voodoo zombies and classic monsters in general, began to see a decline in popularity by the 40s. Reanimated dead were occasionally featured in some of those highly atomic/science/monster movies of the 50s, and they were usually explained more though convoluted science than magic. The next big step in the direction of modern zombies came largely come though the book, “I am Legend,” and the movie, The Last Man on Earth. The character in this story fights for his life against humans who have been physically and mentally mutated. This is a story of one man versus many, and was credited by George Romero for helping to inspire what came next.
In 1968, Night of the Living Dead came out. George Romero originally referred to the creatures in this movie as ghouls. There is little explanation for what caused the ghouls in this movie, but they were many. Though Romero seemed intent to refer to these creatures as ghouls, others in 
the film industry, viewers also, couldn’t help but see a similarity to zombies. The coming years would bring about similar storylines where zombies were flesh-eating monsters gathering in hordes. Then ten years later, Romero solidified the concept of zombies in his sequel, Dawn of the Dead.
Dawn of the Dead set zombies and survivors in a shopping mall, with heavy allegory toward consumerism. Even with Romero’s famous movies, zombies were still somewhat niche. Consider that horror already had some strong trends. There was the rural-set horror of the early 70s, gradually shifting to slasher films. These mutated into supernatural slasher films in the 80s, and the 90s saw an ebb in the popularity of horror until coming back to the slasher genre once again. Although there were many zombie-style movies, including a return to voodoo roots with The Serpent and the Rainbow (‘88), a film about scientific reanimation in the aptly named Re-Animator (‘85), zombie films were often low-budget, poorly dubbed if foreign, and just honestly, often relegated to bargain bins in the movie stores. Even when featured in such mainstream snippets as Michael Jackon’s Thriller music video (‘84), zombies just kind of fell to the background. Things however, were about to change, not with movies or books, but this time around, with videogames.
Zombies made for excellent videogame villains. They’d been featured in games as early as the Atari 2600, but even in some of the more famous games like Ghost and Goblins (’85), Zombies Ate my Neighbors(’93), or House of the Dead(96), zombies were more like obstacles to dispatch. Then a game came along that truly brought the player into the horror world of simply trying to stay alive amidst overwhelming odds.
Resident Evil was released in 1996. The game required survival in and around a mansion, one that among other things, had roaming bloodthirsty zombies. Players unraveled a narrative of grisly experiments that led to monstrous results. Resident Evil 2 (‘98) set characters in a city overrun by zombies. The story of the outbreak was expanded upon to explain an experimental virus led to the creation of the zombies. Both games captured the sense of struggling to survive, of managing weapons and ammunition, and often running and hiding. Both games, and most that followed in the series, were undeniably popular. Many modern filmmakers say they were inspired to make something involving zombies largely because of playing Resident Evil games back in the 90s.
On a personal level, I loved the games too. In fact, after many nerve-wracking hours exploring the stories, I wondered why the hell no one had done what I thought obvious and made a Resident Evil style movie. Though I eventually realized my own ignorance, my experience with the games did leave me with an interest in zombies. In fact, a whole generation was introduced to this monster through these games, and we were, primed for more.
As the 2000s hit, younger generations seemed much more receptive to zombies. This was proven with the popularity of a Dawn of the Dead remake, and Zombieland. Coming years also brought The Walking Dead series, and 
countless others. Unfortunately for Resident Evil, when the movie adaptation came out in 2002, it seemed bent on straying away from the basic formula of survival horror that had been so popular in the games.
Of course, there are far too many zombie movies to mention, both nowadays, and over the summary of the past decades. I only touched on the more famous media that helped to establish the definition of a typical zombie. Which is to say, a plague usually first spreads a virus. Next, zombies only come about after being reanimated. Although voodoo is typically left out of the modern zombie equation, sometimes mysticism plays a part in the zombie outbreak. Essentially, all of the past media involving zombies has been implement in some form or other. The steps to getting where we are today with zombies have been incremental, but also so big at times that one might even call these changes, mutations. Well, though it’s only in the form of entertainment, there is a certain fascination in the idea that the zombie has over time, and in often in great leaps, evolved.