Rare Earth: Why Complex Life Is Uncommon in the Universe is a 2000 popular science book about xenobiology by Peter Ward, a geologist and paleontologist, and Donald E. Brownlee, an astronomer and astrobiologist, both faculty members at the University of Washington. The book is the origin of the term 'Rare Earth Hypothesis' which, like the book, asserts the concept that complex life is rare in the universe.