Reminder that Orcas are the best example of race realism and it being completely natural.
Resident and Transient Killer Whales separated from one another hundreds of thousands of years ago. They have kept their populations completely separate, even when populations often occupy similar spaces and hunting grounds. They use different vocalizations (languages), have superficial differences to one another, and engage in completely different behaviors. They're classified as "sub-species," but are much closer related than other sub-species within other animal groups. Normal genetic differences are not enough to completely separate them, only geographical and visual (racial) differences.