There is a tribe in Western Africa known as the Dogon people. They have a tradition of having been visited by beings who taught them various skills. The Dogons explain that these beings come from the sky, from a star we know as Sirius. The Dogons explain that this star is actually two stars, one of which cannot be seen. One star circles the other.
Supposedly the Dogon tribe had been isolated and undiscovered until the Twentieth Century. Then, early explorers learned that the Dogons knew about Sirius and its companion star. The explorers were amazed at this knowledge, because the Dogons had no telescopes or other equipment with which they could have made these discoveries. The tribe hadn’t had contact with other people until now, so how on Earth did they know about Sirius? Aliens, of course. Had to be aliens.
Somewhere in Dogon history, someone told them about the star Sirius and its invisible companion. Clearly, the Dogons did not discover these facts on their own. The question is, who told them about it? If the Dogons had really had no contact with outside human societies until the early 20th Century, then it might make sense to believe that some non-human society made first contact.Still…
The question boils down to which is more likely – that aliens made contact and told the Dogons about Sirius, or that human contact was made with the tribe earlier than was assumed..