The evolution of life on Earth over the past four billion years may be the most lavish, and successful, R&D program in history. The human being, capable of making tools and solving crossword puzzles, is one remarkable product, but so too is the squid, which mastered jet propulsion millions of years before NASA, and the bacterium–the original inventor, three billion years ago, of the free-spinning wheel. Natural selection has exploited almost every physical and chemical phenomenon, including electricity, which is used by both sharks and the duckbill platypus to sense potential prey.

Yet these phenomena are little more than surface decoration within the context of our complete evolutionary story, brilliantly recounted by University of Oxford biologist Richard Dawkins in The Ancestor’s Tale: A Pilgrimage to the Dawn of Evolution ($28, Houghton Mifflin). Borrowing the structure of Chaucer’s Canterbury Tales and taking as his premise that “biological evolution has no privileged line of descent and no designated end,” he counters our temptation to view natural selection as purposeful, a laboratory working toward the goal of making fully functional humans. Instead he tells the epic in reverse, starting with us and moving backward, chapter by chapter, through each convergence with a common ancestor on the tree of life–chimpanzees, marsupials, amphibians, flatworms, fungi and amoebae, eventually reaching the earliest bacteria.

The fact that Dawkins is able to chart our entire history through just 40 such convergences speaks powerfully to the deep unity of life. More significant, his narrative puts front and center the single essential invention underlying all others: the ingenious genetic mechanism, now performed primarily by DNA, of heredity.