Erich von Däniken built a career taking this mentality to the next stage, attributing the civilisations of ancient America and God knows what else to aliens from beyond the stars. I freely admit falling for it myself, as a kid. It was exciting and romantic. Unfortunately it was also a defence shield for smug, cosy westerners who liked to believe they were the epitome of human knowledge. It was camouflaged as a sense of wonder when in fact it was designed to shut down the imagination and the sense of wonder completely. What, humans built those fantastic pyramids and temples and palaces in the middle of the jungle? Humans more gifted than us? You want me to celebrate the wonderful thing that is the diversity of human ingenuity? Don't be ridiculous. It must have been aliens.
You can still build quite good science fiction on the notion of early alien intervention. Unfortunately, hard on the tail of Erich came Roswell and the Greys. Somehow they all got tied together and now the Greys are the archetypal, default alien - thin, grey, spindly, with a penchant for intervening in our prehistory. They are invoked as an explanation for something alien that requires no further thought.
I'm going to quote myself in an online rant I posted on this subject a few years ago, since I've already substantially paraphrased it. To save you following the link the apposite paragraphs are:
"... science fiction is meant to evolve. Here in the early twenty first century, every grey alien is a nail in the coffin of originality. It is like equipping every fictional starship with a warp core and dilithium crystals, just because that's how Trek does it. It's safe — it's a way of hanging up a sign to say that we don't intend to explore this particular avenue any further. "These guys are the aliens, okay? So don't bother your pretty little head — now let's tell the rest of the story." But in a story that has aliens, the aliens should be the freakin' story. Otherwise, why are you bothering with aliens at all?And it is all of the above that lies as a fundamental flaw at the heart of Indiana Jones & the Kingdom of the Crystal Skull and means that it could never, ever be a great film. This is a great shame because it is undeniably fun. It doesn't hide Indy's advanced years; it makes a virtue of them. It has all the required chases and adventures and sword fights between two combatants who are each standing on a jeep driving very fast down parallel roads in the Amazon jungle (which of course is positively riddled with parallel roads). The opening scenes, as well as being prime Indiana are also chilling in a way that lies at the heart of the 1950s. Cate Blanchett is a superb uber-bitch baddie. Spielberg very wisely uses CGI as sparingly as he can - most of the stunts are with good old fashioned stuntmen and models and special effects. It's almost vintage.
I'll tell you why. Asimov deliberately chose a humans-only universe for most of his output, because he found the alternative of his contemporaries — a Campbellian, mixed-species-but-humans-triumphant universe — too similar to the barely veiled prejudice he had encountered as a Jew growing up amongst gentiles. By eliminating the aliens, he bypassed the problem. Since then, science fiction has evolved to be able to accommodate aliens without necessarily classifying them as Jews, blacks, communists or generally un-American. Sadly, the advance of the greys is a step back towards the Campbell days. Aliens are rendered instantly understandable and dealable with; and by implication, it's immediately them vs. us, and we had better be the winners.
Science fiction is better than that. We are better than that. I'm not afraid to be challenged. Give me aliens. Give me intellects vast and cool and unsympathetic, or give me physical forms and intelligences shaped by evolution on an unimaginably alien world. But unless they're lined up with their backs to a wall and blindfolds over their pupil-less eyes, don't give me any more greys."
Yet, Indy found fame battling bad guys under the McGuffin of mystical forces that were never entirely understood and best treated with reverence. Was that really the Angel of Death in the Ark? Did Christ really drink out of that cup? We never really knew; we were never meant to know. But we were on the edge of our seats waiting to see what happens next.
Indy4 brings in the Greys. "Oh look," we say dully, "it's the Greys. Pass the popcorn."
Um. Would now be a good time to add "spoilers ahead"? Better late than never.
Incidentally, I intend to see Prince Caspian for the simple fact that Eddie Izzard does the voice of Reepicheep. Eddie Izzard was born to deliver Reep's best lines. "Cake or death, poltroon?"