For Those Who Don't Believe in Zombies

On the 30^th of April, 1962, at 9:45 PM, Clairvius Narcisse checked himself into the Albert Schweitzer Hospital in the town of Deschapelle in the Artibonite Valley of Haiti. Narcisse had been sick for some time, complaining of fever, body aches, and general malaise, but just recently he had begun coughing up blood. His condition deteriorated rapidly. Attending physicians noted that Narcisse suffered from digestive disorders, pulmonary edema, hypothermia, respiratory difficulties, and hypotension. His sister Angelina would later recall that his lips turned blue, or cyanotic, and that he reported tingling sensations, or paraethesias, all over his body. On the morning of May 2 his two attending physicians, one of whom was American and the other American -trained, pronounced Clairvius Narcisse dead. His body was identified by his oldest sister, Marie Claire, who affixed her thumbprint to the death certificate, and he was buried the next day. Eighteen years later, Angelina Narcisse was walking through the village marketplace when she was approached by someone claiming to be Clairvius Narcisse,  he identified himself by a boyhood nickname which had not been used for years and which was known only to members of the immediate family.  He said that shortly before he was pronounced dead, he felt as if his skin was on fire, with insects crawling beneath it. He heard his sister Angelina weeping as he was pronounced dead, felt the sheet being pulled up over his face. Horrifyingly, although he was unable to move or speak, he remained lucid and aware the entire time, even as his coffin was nailed shut and buried. He even had a scar which he claimed was sustained as one of the coffin nails was driven through his face. He felt the sensation of floating above the grave. There he remained, for how long he did not know, until the coffin as opened by the bokor (or witch doctor) and his henchmen, who him sent him away to a sugar plantation that was to be his home for the next two years. On the plantation, Narcisse and some other zombies labored from sunup to sunset, pausing for only one spare meal a day. He would later report that he passed his time there in a dream-like state, devoid of will or volition, with events unfolding before him as if in slow motion. Freedom came two years later. One of the zombies was being beaten by the bokor for insubordination, and in desperation the would-be victim managed to grab a hoe and kill his tormentor. To figure out if this was truly Clairvius Narcisse, Dr. Douyon came up with a series of questions about his intimate family history, which the man claiming to be Narcisse answered correctly. There was certainly no apparent motive for fraud in this case (zombies in Haiti are treated as complete social outcasts). His answers, together with the testimony of Narcisse’s family, neighbors, and physicians, convinced Dr. Douyon that the man claiming to be Narcisse was indeed who he claimed to be. To get to the bottom of this specimens of the zombie powders, from several different bokors, in several different locations were found,  three classes of ingredients were common to all the preparations: 1) charred and ground bones and other human remains, 2) plants with urticating hairs, spines, toxic resins, or calcium oxalate crystals,  and 3) puffer fish. The puffer fish contains tetrodotoxin, one of the deadliest poisons known to man. Easily five hundred times more powerful than cyanide, tetrodotoxin binds to the sodium channels on the nerve cell membrane, blocking transmission of the nervous impulse. Symptoms of tetrodotoxin poisoning include malaise, paraesthesias, cyanosis of the lips, digestive disorders, pulmonary edema, hypothermia, respiratory difficulties, hypotension, aphonia, and complete paralysis. It is likely that an individual poisoned with tetrodotoxin and then buried alive would suffer some degree of brain damage due to lack of oxygen. As Nathan Kline and others have pointed out, the higher centers of the brain, that control will and volition, would be the first to die, while the more primitive parts of the brain, that control vital functions such as heartbeat and ventilation, might still survive, this explains the Zombie like state. 
So if you are one of those people that say "Zombies could never happen", you're already wrong.