User blog comment:Blaziken rjcf/Theory on how an Ultimate Human "works"/@comment-3521654-20110426175423/@comment-34326521-20110426235554

I don't think they can. After all, all the hybrids on the show are always alien+human. As for the Highbreed, they thought that mere contact with an alien species would "contaminate" them, even without mating. Azmuth explained that they were dying and since they didn't want to die alone, they were just trying to take the rest of the known sentient species down with them