Most of us think watching "Walking Dead" or any of the many zombie-themed TV shows and movies out there is just pure, escapist fun. After all, zombies as a concept don't even make much sense. What could possibly happen to turn otherwise normal people into drooling, possibly brain dead, people-eating machines? It's a question asked on Discovery Channel's "Zombie Apocalypse" (Tues. Dec. 18 at 10:00 p.m.), which features real people preparing for the worst and scientists mulling over what could actually happen. The bad news? A zombie pandemic may not be likely or even probable, but impossible? Not exactly.  

Steven C. Schlozman, a Harvard professor and the author of "The Zombie Autopsies: Secret Notebooks from the Apocalypse," talked to HitFix about what would need to happen for people to be transformed into zombies (short answer: a lot). Sclozman explored the topic as a needed outlet from dealing with a bigger, real-life problem -- his wife's battle with breast cancer in 2008 (the good news is that she's fine now). "My kids were little and I was up late watching 'Night of the Living Dead,' and I thought if there were really zombies, I would hope we'd bring them in and figure out what's wrong with them. It's impossible not to wonder what would do that to their brains."

He found zombies compelling for many of the reasons other people do -- pure escapism starring an enemy that's almost sympathetic. "The reason zombies resonate so powerfully is that they're recognizable. The monsters are us, as in 'I've seen the monster and it is us,' so it's hard to make zombies the enemy," he says. "There's also easy to get away from. You can eat a sandwich while trying to get away, they move so slowly. And still we always screw it up [in the movies]."

Having been a fan of horror movies growing up, and having "recognized more consciously the social commentary present in them," he took a considered, academic approach to the topic. "If you were turn a person into a zombie with an infectious agent, and that's what I tried to do in the fake medical paper and the book I wrote, the question is, what would create the victims of this pandemic that would turn them into something resembling zombies? It would be highly unlikely, but, and this is science fiction, it would have to be an engineered virus, and it would have to leave parts of the brain intact or the zombie would fall over."

But how do you create a hungry, "yum, brains" zombie? That was a trickier problem for Schlozman. "Any time you're really sick with a fever, you're never hungry. You don't even feel like eating when you have a cold. But I discovered there are illnesses, and they're indicated in pathological obesity, that make you both sick and ravenously hungry." And if a person happens to have a taste for human flesh, even better!

Of course, that's not all that would have to happen to create a zombie. "You have to mess with, but not entirely take out, their cerebellum and their ganglia, the things that allow them to walk with a certain amount of fluidity so you have that shambling gait. You can imagine all of these things coming together in a perfect storm to create the victims."

Alas, some elements of classic zombie movies just won't fly, even under the best of circumstances. "It couldn't be spread through biting, though, and you can't have the dead rise." 

The professor has his own opinion in the debate over fast versus slow zombies. "Although I find the [fast zombies of '28 Days Later'] likelier, the slow zombies are scarier to me. If something's running fast straight at you and clearly wants to attack and eat you, you don't have time to think. But if it's stumbling after you and looks like your girlfriend and you hope it is, there's all this thinking that we do that makes the slow zombies more dangerous."

Oddly, the unlikeliness of zombies actually happening, fast or slow, is apparently a disappointment to some people.  "At Comic-Con, people ask if zombies could happen, and when I say no, they boo," he says, laughing. "Guys, you don't want zombies to be real, come on."