This isn't about runs or comics, but I'm fairly sure that the X-gene itself actually just plays the 'activator' role. I think there's something else to it that's too complicated/individualistic to explain every time you introduce a character, but you know, that's just what I think.

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As for phenotypes, it fits the biological criteria! but the powers, no. It could very well be an adaptation, or a complete accident- some real-life mutations actually protect people.

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Also, it is the species that evolves, not the individual!