Chastity said:
Yeah, but none of those really apply to Psykers, as far as we know there's no "Psy-trait" along the lines of sickle cell trait which would allow for a selection advantage for people with partially psychic tendencies, nor is there any evidence for kin selection (again very much the opposite, an unchecked Psyker is a danger to everybody).
Ah but that's as far as we know. A single psy gene might give you excellent hunches and intuition which keep you alive and help you prosper (rather like fate points). We know the Navigator gene is a hereditary genetic trait.
There's other possibilities with Psy emergence.
Time-delayed genes left behind by ancient Slaan seeded throughout humanity. Some evil plot by the Deceiver. Direct intervention from the emperor. A side effect of humanities constant exposure to the astronomicon... who knows.
