 In particular, Langford questioned the scattered usages of the term "telepathy" and the genetic engineering of humans capable of life in space and underwater without suits when suits would surely be more economical and avoid creating slave races dependent on high technology to survive.He found the most questionable decision to be the repopulation of Earth's ecosystem by human species engineered to be unintelligent, though noted that "the initial premise once accepted, this is good, striking stuff".Subsequent reviewers have characterized the book as "dystopian", featuring a "freak show of genetic engineering", and that it feels more like science fiction than science, in contrast to "After Man" and "The New Dinosaurs".