Harper's publishes Wade Davis' 1983 study into the pharmacology of zombies. Davis investigated the source of Haiti's belief in the living dead:
From ethnopharmacological investigations, we know that [tetrodotoxin] poison lowers the metabolic rate of the victim almost to the point of death. Pronounced dead by attending physicians who check only for superficial vital signs, and considered dead by family members and by the zombie maker, the victim is buried alive. Undoubtedly, in many cases the victim does die, either from the poison or from suffocating in the coffin. The widespread belief in the existence of zombies in Haiti, however, is based on those instances where the victim receives the correct dosage of the poison, wakes up in the coffin, and is dragged out of the grave by the zombie maker.
You can read an excerpt from the new (paywalled) Harper's piece on zombies in Haiti. Mother Nature's own versions here. The above video – not for the faint of heart – illustrates how to un-make a zombie.
The Dish 