The Tangled Tree: A Radical New History of Life

by David Quammen

This is radically different, Sonea and Panisset claimed, from evolution as described by Darwin, who focused on animals and plants. Animal and plant species, as well as other eukaryotic species, arise mainly by genetic isolation. Bacteria are never so isolated. Instead of tortoises and mockingbirds marooned on islands, mutating and adapting, diverging slowly into distinct subspecies and eventually new species, finally reaching a point where they can’t or won’t mate with other populations—instead of that, you have relentless bacterial togetherness. You have genes oozing sideways all over the planet, from one bacterial strain to another, like pulsing juices inside a gigantic, invisible version of the Blob.