The Twelfth Planet:

Over the years, startling evidence has been unearthed, challenging established notions of the origins of Earth and life on it, and suggests the existence of a superior race of beings who once inhabited our world. The product of thirty years of intensive research, The 12th Planet is the first book in Zecharia Sitchin's prophetic Earth Chronicles series -- a revolutionary body of work that offers indisputable documentary proof of humanity's extraterrestrial forefathers. Travellers from the stars, they arrived eons ago, and planted the genetic seed that would ultimately blossom into a remarkable species...called Man.