One of my favorites. Genetics, specifically Teratology (the science of monsters) has always fascinated me. Something as simple as a deficiency in the quantity or efficacy of some protein or signalling molecule can cause it to be completely absent. Thus some critical piece of information that the cells require is lost, resulting in malformations.
Along with an interest in genetics, neuropsychology has intrigued me in that if a single molecule can cause physical malformations, what happens to the thought process of those missing a critical piece of information in the brain. A mental malformation is not easily as visible as a physical one.
“Just as there are physical monsters, can there not be mental or psychic monsters born? The face and body may be perfect, but if a twisted gene or malformed egg can produce physical monsters, may not the same process produce a malformed soul?
Monsters are variations from the accepted normal to a greater or a less degree. As a child may be born without an arm, so one may be born without kindness or the potential of conscience. A man who loses his arms in an accident has a great struggle to adjust himself to the lack, but one born without arms suffers only from people who find him strange. Having never had arms, he cannot miss them. To a monster the norm must seem monstrous, since everyone is normal to himself. To the inner monster it must be even more obscure, since he has no visible thing to compare with others. To a criminal, honesty is foolish. You must not forget that a monster is only a variation, and that to a monster the norm is monstrous.”
― John Steinbeck, East of Eden