The time is in the distant future. Humans have advanced and spread out into the stars. We have become explorers again. Alien life still has not been found.
Upon arrival to the nearest neighboring star-system(alpha centauri), Humans make the most important discovery in the history of human civilization. Or at least, what they thought was the history of human civilization.
Our explorers make the discovery that humans once lived in this star system, and now they are trying to find out if humans started here, or on earth.
All of history is about to be rewritten.