The book begins with a creation myth that parallels evolutionary concepts, where life begins as bubbles in a puddle of soup under the radiance of Father Sun and the gentle glow of Mother Moon. The evolutionary tree of life becomes a literal part of the story, buried up to its branch-tips (the "islands") in an ocean of Time that just keeps getting deeper and deeper. This is the world that Shanleya explores by canoe, learning the essential characteristics of closely related plants on each island she visits.