witches can zombify a person by killing and possessing the victim's body to force it into slave labor. After rail lines were built to transport migrant workers, stories emerged about "witch trains". These trains appeared ordinary, but were staffed by zombified workers controlled by a witch. The trains would abduct a person boarding at night, and the person would then either be zombified or beaten and thrown from the train a distance away from the original location. Origin hypotheses Chemical Several decades after Hurston's work, Wade Davis, a Harvard ethnobotanist, presented a pharmacological case for zombies in a 1983 article in the Journal of Ethnopharmacology, and later in two popular books: The Serpent and the Rainbow (1985) and Passage of Darkness: The Ethnobiology of the Haitian Zombie (1988). Davis traveled to Haiti in 1982 and, as a result of his investigations, claimed that a living person can be turned into a zombie by two special powders being introduced into the blood stream (usually through a wound). The first, ("powder strike"), includes tetrodotoxin (TTX), a powerful and frequently fatal neurotoxin found in the flesh of the pufferfish (family Tetraodontidae). The second powder consists of deliriant drugs such as datura. Together these powders were said to induce a deathlike state, in which the will of the victim would be entirely subjected to that of the bokor. Davis also popularized the story of Clairvius Narcisse, who was claimed to have succumbed to this practice. The most ethically questioned and least scientifically explored ingredient of the powders is part of a recently buried child's brain. The process described by Davis was an initial state of deathlike suspended animation, followed by re-awakening — typically after being buried — into a psychotic state. The psychosis induced by the drug and psychological trauma was hypothesised by Davis to reinforce culturally learned beliefs and to cause the individual to reconstruct their identity as that of a zombie, since they "knew" that they were dead and had no other role to play in the Haitian society. Societal reinforcement of the belief was hypothesized by Davis to confirm for the zombie individual the zombie state, and such individuals were known to hang around in graveyards, exhibiting attitudes of low affect. Davis's claim has been criticized, particularly the suggestion that Haitian witch doctors can keep "zombies" in a state of pharmacologically induced trance for many years. Symptoms of TTX poisoning range