Acceptance is not as important an issue in The Plains of Passage as it was in The Mammoth Hunters: Ayla is accepted easily by five different Cro-Magnon communities.

Love, on the other hand, continues to be important as Ayla and Jondalar cement their relationship, and jealousy is no longer a disturbing factor. Ayla and Jondalar, especially in their lovemaking, become models of giving and sharing for a young girl who was a victim of rape and does not want to mate. The most pressing question in Ayla and Jondalar's relationship is when and if their love will express itself in the form of a child, Ayla, the Cro-Magnon superwoman, has figured out that men impregnate women during sexual intercourse and has used a drug as birth control to prevent pregnancy on their journey. Jondalar, however, worries whether Ayla will ever get pregnant and have a child of his heart and spirit. By the end of the book, the issue is resolved ludicrously as both Ayla (after a graphically described lovemaking scene "with a secret") and her beloved horse Whinney are pregnant.

Because The Plains of Passage is a journey novel with such natural hazards as glacial cracks, sudden floods, quicksand, freezing rivers, and snow-blinding ice, one might expect the conflict of humanity and nature to be an important theme. However, Auel is more interested in human relationships. The importance of tolerance, equality, and humane behavior arises out of Auel's concerns with racism and sexism.