So, why did Romero's zombies come back to life in the first place?
 

I've always kind of wondered that, what I gather from the movies is they only have theories, like an air borne virus spreading. But, does anyone know the real reason?? Thanks

They never actually say in the movies, they just throw out theories. i think they left it up in the air on purpose. The mystery makes it creepier. Fear of the unkown and all that.

Plus, it'd seem kinda forced if they actually found the reason they came back. If all they have is theories it makes it seem more...well, a movie about zombies isn't going to be realistic, but them only having theories adds at least some realism to it.

thats easy!!
 

They came back because Heaven was closed and Hell was full of French people!!

Bless you all!!!

isn't it pretty much a given that hell is full of french people?