Birth control.Originally Posted by Crocodile
A. The alien's breed rate was much higher than one of human, so if they don't do that Earth would soon be overrun by the other species.
B. They are not natives of this planet and they were allowed to settle under condition that they control their breeding themselves. Apparently they didn't observe this condition.
C. I can see where you are drawing parallels but I don't think that this episode can be a valid example for our discussion here. The aliens were not humans to begin with.