What are the motifs in Cloud Atlas by David Mitchell?

Continuity of life and reincarnation are recurring ideas in the story. The continuity and rebirth of life is a repeating theme throughout Cloud Atlas. All of the main characters - Adam Ewing, Robert Frobisher, Luisa Rey, Timothy Cavendish, Sonmi-451, and Zachry - have a comet-shaped birthmark between the shoulder blade and their collarbone. In addition, there are subtle references to reincarnation, such as Luisa's being familiar with Frobisher's "Cloud Atlas" concerto, even though it is highly unlikely that she has ever heard it before.