- You may be looking for the human descendants from the Pre-Super Genesis Wave Timeline; see Overlanders.
Sharing the Planet
In the modern day, humans have been shown to coexist and work alongside Mobians with little to no internal conflict, with most towns, cities and settlements inhabited with varying amounts of either races. There are, however, locations that seem to be home to no, if not very few humans, such as the primarily Mobian-centric Kingdom of Acorn. (StH: #252, #257)
Like their Mobian counterparts, all human individuals can vary in their moral alignment, good or bad. One of the worlds biggest threats is the scientist Dr. Eggman, a human, who plans to dominate the whole planet and its inhabitents, employing various lackies and underlings-human or Mobian-to serve the Eggman Empire. (StH: #252, SU: #83)
Any conflicts that had occurred between humans and Mobians in the past may be purely circumstantial with race/species not being at the centre. Nonetheless, hostilities between mainly human-based and Mobian-based fractions have existed. The father of Nigel Acorn, the current King of the Kingdom of Acorn, was said to have been "kept on edge" by G.U.N. in older times. (SU: #87)
One of the reasons between conflicts between the two factions in the past would be the pollution and destruction of natural environments performed by some humans, with Dr. Eggman being one of the main examples of humans performing such behaviors.