Excerpted as is from the Battlestar Galalctica FAQ
attlestar Galactica was the brainchild of Glen A. Larson, and evolved from an earlier project called "Adam's Ark". Larson had pitched the show in the late 60's, the same time that the original Star Trek was in its death throes, but the project was put on the backburner. In the intervening years, Larson worked on many popular television programs, including "It Takes a Thief", and "McCloud". It wasn't until Star Wars hit movie theaters in 1977 that Larson's pet project became something viable.
Larson once remarked in Science Fantasy Film Classics (October 1978):
Adam's Ark was sort of about the origins of mankind in the universe, taking some of the biblical stories and moving them off into space as if by the time we get them to Earth, they're really not about things that happened here, but things that might have happened someplace else in space. It was influenced by Von Daniken's "Chariots of the Gods" and some of those things... Adam's Ark helped bring a focus into what my concept had been. Ultimately, Battlestar Galactica is my original idea refined down to where I now have fixed on what my point of view is on how all humans throughout the galaxy probably evolved from some mother colony.