All organisms and species are transitory, yet life endures. The origin, extinction, and evolution of species--interconnected in the web of life as "eternal ephemera"--are the concern of evolutionary biology. In this riveting work, renowned paleontologist Niles Eldredge follows leading thinkers as they have wrestled for more than two hundred years with the eternal skein of life composed of ephemeral beings, revitalizing evolutionary science with their...