There's a learned doctor of genetics on BL board that will dispute the 'gene' theory and tell you that genes do not work that way.
Even so, I'm convinced that spanking is something probably born with all spankos and triggered very early in our lives. I was never spanked as a child (and neither later), and to my knowledge never saw a spanking as a child, but from very tender age, I was interested in the subject, until when I was nine an incident transformed me in a fully converted spanko to this day and I'll probably die before my interest will die.