Handmaid's Tale

If the Republic of Gilead's main goal was repopulation of the country, why wouldn't they have younger men than the Commander be the ones with handmaids and then send the older, infertile men to a place like the colonies? And perhaps I have just forgotten, but the discussion in class brought up the Historical Notes and how the lecture was about Caucasian Anthropology. I don't remember any references to minority races in Gilead. How did Cambridge, MA become all white in the transition to Gilead?