"The Neanderthal Parallax" is a science fiction trilogy written by Robert J. Sawyer. It explores the concept of parallel universes, where one universe is inhabited by Neanderthals who evolved instead of modern humans. The story delves into the cultural and scientific implications of this alternate reality, highlighting the differences in societal development and technology. The trilogy begins with "Hominids," where a Neanderthal physicist accidentally crosses into our world. As he interacts with modern humans, themes of identity, evolution, and coexistence are examined. The series raises questions about what it means to be human and the potential for understanding between different species.