"Gay" actually evolved over the last century or so. It did not have an article or two on the innernetz by guys saying "Comics are our new mythology!" that had the fanboy crowd say "Yeah - that's it! Cuz I'm actually kinda self-conscious about being a comic fan, so I'll embrace and adopt the gravitas of 'mythology' and I can feel better about myself!" You can't point to where "gay" changed like you can "mythology" - and that's what makes it organic, and therfore - an evolution.
Evolution in language is like a game of telephone. When someone says "lets call it mythology" and everyone joins in, that's a consensus decision, not evolution.
Seriously - its not that difficult a distinction. Or rather, if it IS that difficult a distinction, it makes my broader point about the hazards of consciously manipulating language; it doesn't just impact what we say, it impacts how we thinking about the underlying abstract concepts. Dumbs us down.
And really - why did we need 'mythology' to make us feel better about it in the first place? I have no shame about loving comics, superheroes, etc. As far as I'm concerned, those words have their OWN gravitas, thankyouverymuch.