 As a result of mankind's technological prowess, evolution is accelerated, producing several species with varying intraspecific relations, many of them unrecognizable as humans.Instead of the field guide-like format of Dixon's previous books, "After Man" (1981) and "The New Dinosaurs" (1988), and instead of the conventional narrative style of most science fiction works, the book is told through short stories, isolated sequences of dramatic events in the lives of select individuals of the future human species imagined by Dixon.The genetically engineered humans of the future, in total numbering about 40 species through the book, occur in several different and diverse forms, with genetically engineered forms first being slave races created to survive underwater and in space without the need of protective gear and suits, described as the "ultimate triumphs of the genetic engineer".