When the Earth Died, Then Was Reborn — Susan Hart

The Scavengers - After a calamity wiped out most of earth's population a hundred years before, the remaining million or so souls has divided up into two basic groups: Men in lodges whose life consists of scavenging for the remains of civilization along the coast, and groups of females who use men as draft animals and for impregnation. Everything was moving along fairly smoothly until the Martians landed. Mountain Of The Ancients - In a post apocalyptic future, earth has reverted to a low-tech system of kingdoms and female leadership, held together by an empress. One couple emerges, Darnel and his fierce wife Betty, who are called upon by the empress to escort her to the Mountain Of The Ancients to coronate a new empress who will take over the reins of power.