In Guardians of the Galaxy, we see many members of the Nova Corps. All of them look human. Late in the film, they refer to Star-Lord as a Terran, so they know of Earth, but it's clear they themselves are not considered Terran. Rocket also refers to Star-Lord as a 'humie' multiple times, which presumably is short for human.

Why/how do they look human, if they're not from Earth?