Humans are non anthropomorphic species that are different from the anthroes characters like Sonic. In both the main IDW and classic continuity, the only humans so far seen are their counterparts of Dr. Ivo "Eggman" Robotnik and his classical counterpart.
Movie continuity[]
In the continuity based on the sonic film franchise, humans originated and lived on Earth. (Sonic the Hedgehog 2: The Official Movie Pre-Quill)