When Jeph Loeb wasn't single-handedly ruining the entire Hulk brand, he revealed that Wolverine, Sabretooth, Wolfsbane, Feral, Wild Child, Romulus (who? Exactly...but laaaater), The Native, and etc. where not just mutants, but were a branching species of wolf-mutants who during their existence hated members of their own sub-species based on hair color...a trait Wolverine & Sabretooth would inherit, because apparently all this time they hated each other on impulse because Logan is brunet and Victor, blond, has more fun...