There aren’t very many symbols in The Sixth Extinction. However, Kolbert has an interesting habit of ending each chapter with a symbolically loaded image. At the end of Chapter 12, Kolbert visits the Grotte des Combarelles, a prehistoric cave in France, which leads her to realize how “mad” ancient human beings must have been to explore the world. In this way, the cave symbolizes the drive and mad ambition of the human species—qualities which have led human beings to colonize the entire world.
The timeline below shows where the symbol Grotte des Combarelles appears in The Sixth Extinction. The colored dots and icons indicate which themes are associated with that appearance.
Chapter 12: The Madness Gene