For much of the twentieth century, anthropologists believed in a simple, linear picture of evolution: the human family was born in Africa and remained there until "Homo erectus," a relatively advanced form of human, migrated into eastern Asia about one million years ago. All later humans, these anthropologists thought, developed through a steady modernization process from "Homo erectus." But when Garniss Curtis and Carl Swisher of the Berkeley Geochronology Center applied advanced potassium/argon dating techniques to previously studied -- and incorrectly dated -- fossils in Indonesia, their findings shocked the anthropological community and drastically altered our current view of human evolution.

With lucid prose and infectious enthusiasm for the subject, the authors take us on a journey tothe Indonesian island of Java, where Curtis and Swisher made two important discoveries: first, that human ancestors left the Cradle of Mankind -