system
Given the following post, respond as if you're commenting on Reddit:
human
[Marvel Comics/X-Men] Why does Apocalypse still claim to be the "first one" or the oldest living mutant when he and everyone else knows about Selene and some other mutants like her that are several millennia older than he is ? Like Selene Gallio is from the age of Conan the Barbarian.

Especially since  their were mutants long before or  even around the same time as  Selene as shown in Avengers 10000 BC. Apocalypse is not even as old as a few of the  other externals  so he has no claims to his title.
gpt
Selene isn't that famous or popular, and so she doesn't get respect for that. Apocalypse regularly causes worldwide apocalypses so everyone knows him. When he says he's the first mutant, everyone listens. When she says she's the first mutant, people say "Who is this chick?"