This is the first of Butler's series, "Xenogenisis," the second being Adulthood Rites, and Imago the third (see this database). The Oankali's powers include being able to cure cancer, increasing human strength and disease resistance, and healing the planet of the blight of nuclear war. In connecting with one of the characters' bodies, for example, the Oankali tell him that they need to allow his body to teach them about cancer: "Your body knows how to cause some of its cells to revert to an embryonic stage. It can awaken genes that most humans never use after birth. We have comparable genes that go dormant after metamorphosis. Your body showed mine how to awaken them, how to stimulate growth of cells that would not normally regenerate." (236)

The Oankali are genetic engineers and need the interbreeding with the humans to continue their progressive evolution. They are a brilliant, peace-loving, pleasure-loving creation, but for most of the humans the idea of interbreeding is abhorrent and they cling to their "humanness" as though it were the ultimate form of creation. The novel raises questions about healing and illness, especially when the means of healing may be seen as "alien" to what we know as real, true. It also critiques Xenophobia, linking it to the maintenance of diseased bodies, as well as a diseased planet.