There are three taboos for Alchemists; Do not transmute gold, do not act against the government, and do not attempt human transmutation. Two of these rules come from the government itself, either to protect itself or to protect the economy, but the third is almost a natural law. Anyone who attempts Human Transmutation faces severe consequences, as evidenced by both the brothers and other characters throughout the series. Despite the warnings and results of this phenomenon, there are still alchemists who are willing to brave the consequences for what they perceive the possibilities to be. But what exactly is Human Transmutation, and what is so taboo about it?
Fullmetal Alchemist: Brotherhood follows the story of Edward and Alphonse Elric as they seek to acquire the Philosopher’s stone. The boys believe that this will grant them the power to return Al to his human body which was lost in a tragic human transmutation accident. Ed also lost portions of his own body in the same incident. Though Al does eventually return to his mortal body, the boys learn the truth about alchemy and don’t use the stone to accomplish this task.
Types of Human Transmutation
The most common type of Human Transmutation that is attempted in the show is resurrection. While this is the most commonly attempted form, it is also the one least likely to succeed. There is nothing that is truly equivalent to a human soul and therefore the law of equivalent exchange cannot be satisfied. There is also some implication that once a soul leaves the mortal shell that it is beyond the reach of alchemy.
Another known use is in the attempt to create artificial humans or homunculus. While this is a largely theoretical form of transmutation it is expressly forbidden by law as the government fears alchemists with private armies. This would be a human shell with some sort of animating force, but no independent willpower; the perfect private militia.
There is also Human Soul-binding which is just the general manipulation of souls, and this has only really been successful once, with Al. In theory, this is extracting a soul from a mortal body and infusing it into an iron vessel, generally some sort of armor. Iron allows the blood rune to bond. Even in the best of situations this is temporary, the empty body must remain alive for the soul to remain vital, and the vessel and soul will eventually reject one another as incompatible. There is only one known example of a soul being bound into a living body which is Barry the Chopper.
The final version of human transmutation is the creation of human chimeras. This is the blending of humans with animals to create a unique creation with some attributes of each. Without the Philosopher’s stone, only Shou Tucker is known to have attempted this with his wife and daughter. However, the government itself with portions of the Philosopher’s stone was able to create far more viable combinations that were used strategically. Importantly to note, chimeras can be made without humans so only those human hybrids would be included in the human transmutation category.
Known Consequences for Human Transmutation
Ed, Al, and a mentor of theirs Izumi are the only known people to suffer any natural consequences for human transmutation. Shou is killed, but by an assassin not by nature. Generally portions of the caster's body are taken in trade, as the equivalent exchange, and this is called Rebound. Ed lost his left leg, Alphonse lost his entire body, and Izumi lost some of her internal organs. All three were attempting resurrection. The size of body part taken seems related to the size of the human being transmuted. For the boys an adult woman, for Izumi an unborn child. Each of the three failed to resurrect their loved one, and suffered the consequences regardless.
Additionally in punishment for playing the part of God, the alchemist is dragged to the Gate of Truth to face a God-like creature. This is perhaps God himself although this is not explicitly stated. In return for this, the alchemist gains extreme knowledge and the ability to perform transmutations without a circle. In this sense it may sound like a reward, but it is in this moment that their physical forms are mutilated, and it is implied that this interaction can affect the alchemist’s soul as well.
Summary
Despite harsh physical, mental, and legal consequences for human transmutation alchemists sometimes still make the doomed attempt. Grief over the loss of a loved one, desperation to maintain status, or determination to save the life of a brother may be the motivation but regardless, the caster’s emotions must be strong enough to dismiss the taboo.
Some of these taboos come from human law and others from natural law which may not help the situation. The boys certainly would have been willing to break human law to revive their mother, but had they known the natural consequences of their actions they likely would not have continued down that path.