Homo-sapiens. As it stands, humans are the dominant race on the planet, and while mutants are born from them, there are some out there (both human and mutant) that see each other as separate species. Since the existence of mutants went public, humans for the most part have reacted in fear. This fear generally takes the form of a "you leave me alone, I leave you alone" state of mind. In quiet Salem Center, NY, the humans live their lives choosing to ignore the mutant around them.
There are some though, who see mutants as a threat to the continued existence of the human race. These radicals would see mutants everywhere tracked down, tagged like animals, and registered. In the worst case, there are humans who want nothing more than the absolute annihilation of mutants everywhere. Many have tried, in the form of religious zealotry, scientific experimentation, and even rogue government factions.
There is a flip side to this coin, however. Many humans accept mutants for who they are. The ignore the propaganda and choose to make their own informed decisions on a case-by-case basis. Unfortunately, they are not as loud or active as their mutant-hating counterparts, and the humans caught undecided tend to by swayed by the fear and hate mongering.