Is the existence of civilization on Earth a result of contact from inhabitants of a planet in the sysyem of the star Sirius prior to 3000 BC? There are tribal cultures in present-day Africa whos most sacred and secret traditions are based on this theory. Central to their cosmology is a body of knowledge concerning the system of the star Sirius that is accurate in detail, including specific information only recently accesible to modern science. The author traces the traditions of the Dogon and three related tribes back 5000 years to the ancient Mediterranean cultures of Egypt and Sumer. He shows a knowledge dependent on physics and astrophysics, which they claimed was imported to them by visitors from Sirius.