The Stuhlinger Effect is the name given to the unexplained reason as to why so many Abnormal-Class entities lack body hair, even if having body hair would be more advantageous evolution-wise.
The Stuhlinger Effect was originally coined by a Nero scientist by the name of Vince Stuhlinger, the man who lead the first studies into why said effect exists, and what purpose it serves. Believing that it was a sort of "intimidation tactic", Stuhlinger ordered that two entities that were affected by the anomaly be placed in the same cell for one day, and their actions to be recorded, detailing any behavior that appeared to sprout from the entities' lack of hair.
The following day, he checked on the investigation to find that the two entities had attacked each other in short engagements all night, but none of their behavior appeared to stem from the Stuhlinger Effect.
After two years of testing, Doctor Stuhlinger discontinued the research, and simply stated that "the lack of hair could be, to put it simply, just a coincidence, and no scientific evidence we have found points to a probable cause of the Stuhlinger Effect.