Bioluminescence is everywhere on earth--most of all in the ocean, from angler fish in the depths to the flashing of dinoflagellates at the surface. Here, Therese Wilson and Woody Hastings explore the natural history, evolution, and biochemistry of the diverse array of organisms that emit light. While some bacteria, mushrooms, and invertebrates, as well as fish, are bioluminescent, other vertebrates and plants are not. The sporadic distribution and paucity of luminous forms calls for explanation, as does the fact that unrelated groups evolved completely different biochemical pathways to luminescence. The authors explore the hypothesis that many different luciferase systems arose in the early evolution of life because of their ability to remove oxygen, which was toxic to life when it first appeared on earth. As oxygen became abundant and bioluminescence was no longer adequate for oxygen removal, other antioxidant mechanisms evolved and most luminous species became extinct. Those light-e