Oof, as a Biology major this hurts. The definition of "Species" is pretty loose really, it just means members of a similar gene pool that are able to breed with each other. There are 6 different ways "not breeding together" is defined, two of them being "Sexual Selection" and "Mechanical incompatibility"

Those two deer, if someone were to mix their gametes in a petri dish could probably produce offspring, but if they live in the same region they are likely classified as separate species because they just don't mate. Perhaps they give off different mating hormones, and don't recognize members of the other species as potential sexual partners, or due to height differences, penis/vagina size differences, they physically cannot have sex.

Even tho humans look very different none of the 6 types of species separation apply to us. Ethnic groups are more like different breeds of dogs.