In my experience, it's all congenital...inborn. Artificial mutation, to my knowledge, has never been successfully replicated or accomplished.

It's never a matter of choice.

[ A sigh. He should be clearer. ]

For us, "manifestation" isn't anything strictly new, though it certainly can feel like it. It's simply the gene no longer lying dormant. Like with eye color often changing in infancy.

[ His clearly never did, those bright blue eyes can be startling in their intensity. ]

Granted, the effects are very different, but the concept is not.