Some theories claim that humanity will grow into separate races, each designed for a specific task. If this is true, then there’s a hint of Nazi-like determination at work in science. Certainly, the idea of “jews” against “whites and aryans,” just like “white masters and black slaves” are all social models built purely on pseudoscience, political paranoia, and exploitation. But there are still some that believe there is suitability (and natural tendency) for humans eventually having segregated races which do not interbreed. Each one tailored to a specific task. This theory will likely yet again be exploited (and developed) for another excuse for supremacists to point fingers toward one human group as a necessary subordinate. Let me say this very clearly as my own conviction.
If you can interbreed, then you have no practical evolutionary reason for segregation or holocaust. To pursue such a thing is a crime against humanity.
However . . . perhaps we can ask if there would be a reason for a co-existence of humanity offshoots. Imagine, for example, a symbiosis between a human-like being that carries many plant-like organs (Mrs.Plant). And the alternate human-like being based on our traditional organs (Mrs.Herbivore). Mrs. Plant and Mrs. Herbivore would be considered as an essential survival unit together. Requiring a climate of certain temperatures, light, soil, and water, they would exchange the proper chemicals to survive off of each other. Strange but possible?