Ketamine is an opioid that is also thought to occur naturally in the human body. When lab animals are subjected to a terrifying attack—an experiment that can’t be duplicated with people, obviously—their brains are flooded with dopamine and other opioids. Artificial ketamine is already known to protect cells destroyed by low blood oxygen in brain injury victims, and an endogenous version manufactured inside the body that accomplishes the same thing would make biological sense. The hallucinations and euphoria that accompany these compounds could provide an additional evolutionary benefit by
...more
