The concept of evil spirits is christian. Buy Jesus and the Twelve boyfriends brand Coven, all others are evil.
Before that everyone saw them as good. Those who could paint, sculpt, compose poetry, music, had perfect pitch, designed buildings, understood machines, were said to have a Daemon. They could do what ordinary people could not, but had no training, just a gift from the gods.
The Greeks did describe the Autistic as such. They were highly valued.
The christian called them Sourcerer, for their knowledge came from a source other than the Bible.
That is when they started burning us at the stake. Still at it.
They destroyed the works of the Greeks, Romans, Math and Science, for they were not mentioned in the Bible. We call it the Dark Age, lit only by the light of burning Autistics, who knew things, and heard voices.
Autism has been called schizophremia, but that term has never been defined, most Autistics report inner dialog, several voices, it does make for writers, and for psychobble idoits who talk of latent schiztypical leanings and wanting to kiss the Devils Arse. Still stake burning.
Art, Science, beauty, did not come from religion or psychobabble, only from those gifted by the gods.
The Greeks called them the Muses, held them in high honor.
It is the best fit to the model of Autism.
Normal development till three would rule out a genetic or neorological cause, for it would be there from day one.
Starting at three, a change in brain wiring, a differance in development giving the child great mental powers.
Then an unchangable lifetime condition, of being somewhat different, and of exibiting unusual talents, and drives.
Aside from christiam conservtive spin, those with a spirit familier have little need for other social life, and strong special interests, often, Science and Medicine. Who taught Newton?
Spirit Familiers are known to run in families over hundreds of years, the Darwins.
Outside blood would rule out a genetic cause.
Many cultures consider them ancestor spirits returning to help, which produces Little Professors, children with the wisdom of adults, and often much wiser than adults. In the Jesus Myth, he was said to be a Little Professor.
Most traditional cultures consider them speakers for messengers of the gods.
They did nothing, they were small children, they were Chosen Ones.
Compare this to self elected elder brothers in black dresses who collect chior boys, or Psych Majors, who learned everything about the human mind in two years at the University.
Both of the latter groups say everything you think is wrong, only I know the Truth!
Chosen Ones are Truth Sayers, they cannot lie, nor will they shut up.
There is no wrath like that of a rejected Messenger of the Gods.
The Gods sent a gift, it was beaten, drugged, and burned at the stake, or nailed to a cross.
Once and repent, the world could be forgiven it's sins, but it did not turn out that way.
Now comes the Judgement of the Gods, Chosen Ones by the millions.