Humans, also known as Hominis, are fairly common in the galaxy. No less than eleven distinct human races exist throughout the galaxy and all seem to have independently developed in their own star systems.
All races of hominis have claimed a unique racial name for themselves.
Hominis from Earth usually go by the nomenclature of Terran or Human.
While the races themselves have almost identical DNA, close enough that interbreeding should succeed, no offspring from interracial pairings have occurred.
Despite the closeness of their DNA, all eleven of the Hominis races have genetic code sequences that do not match any genetic sequences in other Hominis races. It is thought that this unique DNA-level encryption is what prevents interbreeding. The exact mechanism is unknown and likely never will be.