This is not how it works. Race mixing is the exact opposite of evolution, and it is not a force for growth or development of new species. It is the opposite of growth, and it is the extinction of different species. It is the extinction of biodiversity.
If all races bred with each other, then all of the hundreds of different small racial groups would all be gone and extinct, and the only thing left would be one sick and unhealthy group of people who are all the same as each other. If you take any diverse groups of many different things, and you melt them all down together into one thing, then all of what you started with are all lost and gone forever.
Evolution is an extension or an example of the natural universal force for entropy. All things becoming more complicated, spreading and developing outward into new different areas, and new different things being created that did not exist before. It is exactly the opposite force and opposite direction from race mixing. Race mixing is the ultimate force of death, erasing all of the things, and the exact inversion of the universal force of creation.
Animals evolve as one animal is born with a different trait. And as more of these animals are born with this trait, they only breed with other ones that have that same trait. This makes the trait genetically stronger, and ends up as a population where every one of them all have that trait. And now there are two different populations of two different sub species where one group all has the trait and the other group does not. If they all mixed together, the trait would not exist because it would not have been developed in that way. Instead of becoming a solid population, it would just be a random mutation that leads nowhere.
