As humanity spread throughout space, it encountered environments which were increasingly more hostile towards our form and function. On occasion, we may have been able to adjust these environments to suit our frail needs, but as technology continued to advance, we soon discovered that it was far easier to simply adjust humanity to suit the environment. Thus, via genetic modification, new “genotypes” of humans began to rise and spread throughout the systems.
Humanity found that we required a boost in evolution in order to survive. We decided that we could not wait around for evolution, and thus took our mutations into our own, hopefully not incapable, hands. This diversity is now one of modern humanity's defining traits. It's reflected in many aspects of life, in everything from the wonders of genotype specific foods to the regrettable, but thankfully rare, episodes of genotype prejudice which arise from time to time.