George A. Romero is American genre cinema's most thorough "posthumanist," the one most deeply and least conflictedly interested in showing the collapse of all social order and the survival of a very few. (Off the top of my head, the American mainstream hasn't offered a vision in the same bleak vein, save the last reel or so in A.I.) What interests Romero are not acting or plotting: he's a grand-vision artist, and happy to let his materials roam within the confines of budget and genre, so long as he can shape to his will the needed portrait of a series of philosophical crises. Sometimes he can "suffer" narratively, as a result. Day of the Dead and Monkey Shines both take quite a while to build up to the payoffs the genre requires (the zombie movie's first hour is dreadful). But the breakdown of state, community, even individual--in the Dead movies and in The Crazies--makes for a biting dismissal of these institutions' importance, and for our willingness to both depend on them and not be able to defend them.
Whereas in those contagion movies the most intelligent people are often the ones to die at the hands of stupidity, in Monkey Shines the intelligent people are confronted not with a pervasive collapse but with the burgeoning threat. (Had the characters failed in the film, Romero could have then made Night of the Monkeys, where the capuchin villain Ella engineers her monkey friends to violently overtake an unsuspecting public.) The impending and surprising threat of a more powerful Other is at the root of much Romero. The difference between his work and a lot of horror cinema is that he's practically neutral about the outcome. He's not particularly sentimental about most of his characters, and he doesn't play his thrills against the monstrosity of the villains so much as in the empathic threat against the heroes.
In short Romero is interested in dismantling the facades we've put up for ourselves: consider too the consequence of physical helplessness on the protagonist, an athlete. ("Ooh, ooh," chimes the budding psychoanalyst in the front of the classroom, "that's castration!")
I'm getting really intrigued to see how Land of Dead shapes up.