"After Man" used a fictional setting and hypothetical animals to explain the natural processes behind evolution, a concept that proved successful. The success of "After Man" spawned two following speculative evolution books (sometimes called the ""After" trilogy") which used new fictional settings and creatures to explain other natural processes. "The New Dinosaurs", released in 1988, explained the concept of zoogeography and biogeographic realms through a world in which the Cretaceous-Paleogene extinction event never happened and non-avian dinosaurs were still alive. "Man After Man", released in 1990, focused on climate change over the next few million years through the eyes of future human species genetically engineered to adapt to it.