How does Barbara Kingsolver use imagery in Animal Dreams?

In the first chapter, Kingsolver uses a powerful image to set the scene for one of the
questions the novel seeks to address, which is, why can two people from the same
family, exposed to the same influences as children, become so different as adults? Doc Homer gazes at his two young children, Codi and Hallie, as they lie sleeping. They are completely intertwined, almost as one person. It is not possible to see where one body stops and the other begins. When one breathes, they both move; "Their long hair falls together across the sheet, the colors blending, the curled strands curving gently around the straight."