“The history of science fiction is the history of the imagination,” intones Mark Gatiss, narrator of the four-part series “The Real History of Science Fiction” on BBC America starting Saturday night.

Unfortunately, it’s is more like “The Reel History of Science Fiction,” with video and film clips, comments from actors, directors and writers, and the very occasional nod to the origins of the genre — lurid pulp magazines and books.

Science fiction has always been the world of “what if.” What if aliens come to Earth? Will they blow up humanity as in “Independence Day” or come in peace as in “Close Encounters of the Third Kind”? What if dinosaurs can be resurrected through their DNA as in “Jurassic Park”?

“The Real History” splits its examination of science fiction into four parts. The first deals with robots; part two covers space exploration including “2001: A Space Odyssey” and “Star Trek”; and part three covers invasions from outer space — of which the BBC’s “Doctor Who,” which has just marked its 50th anniversary, is a prime example. (The fourth part, about time, wasn’t available for viewing.)

In doing so, the series pinpoints pivots in popular culture where the effects of science fiction reach the general population. For example, “War of the Worlds” by H.G. Wells, published in 1898 and made into a radio play by Orson Wells in 1938, spawned an entire genre of invasion films.

“The Real History” is fat with clips from American and British television and film. Directors John Carpenter (“The Thing”), Joe Dante (“Innerspace”) and Ronald Emmerich (“Independence Day”) give insight on their films.

There are also some very funny tidbits.

Actor Richard Dreyfuss, who starred in “Close Encounters,” remembers sitting at a restaurant with director George Lucas, who glumly said he’d “made a kid’s film. And he had wanted to make an adult film. And we commiserated with the billionaire-to-be.”

That film was “Star Wars.”