Zombies are the animated corpses of dead entities, most commonly human beings. This reanimation can come about in a number of ways, but it is usually a result of either voodoo (or some other form of magic) or mutation (usually due to genetic experimentation). Zombies are usually mindless, though this is not always the case and it can be true to varying degrees. It is not unheard of for zombies to retain small traces of their personality or intelligence. As time passes, however, they tend to be more and more deeply affected by their instinctive desire to consume flesh, and gradually lose the ability to experience other thoughts and feelings.