The "Pliocene Exile Series" is a science fiction book series written by Julian May. It is set in a future where humanity has encountered advanced alien civilizations and explores themes of time travel, evolution, and the consequences of human actions. The series combines elements of fantasy and science fiction, creating a rich narrative that spans different timelines and dimensions. The story primarily follows a group of characters who are exiled to the Pliocene epoch, a period in Earth's history approximately 5.3 to 2.6 million years ago. As they navigate this prehistoric world, they face challenges from both the environment and the alien beings that inhabit it, leading to a complex interplay of survival and adaptation.