Welcome back to Geek.com’s Origin of the species. Each time out we’ll take a look at one of our favorite fantasy, science fiction or horror races or species, delving deep into history, fiction, mythology and etymology. Check out our previous installments on dwarfs, vampires, and robots!

Aliens run the gamut. Which gamut? Every gamut. Decades of pop culture have taught us that aliens can be pretty much anything, from humans with wacky heads to insect-like monsters to floating clouds of gas. But if you ask an average person to describe an alien, or just what comes to mind when they hear talk of abductions or close-calls with UFOs, chances are they’ll tell you about short grey humanoids with big heads, small mouths, and expressionless black eyes: Grey aliens or just Greys for short.

Greys are very much embedded in the human psyche, with a full 43% of alien encounters in these United States said to involve them. The way we see it, there are three reasons for why this could be the case. The first, and most useful for fiction, is the fact that aliens exist and that just happens to be what they look like. Of course, that’s something best left for our series on conspiracy theories, as we’re sure the Geek.com audience wouldn’t buy the outlandish idea that an alien race would evolve to look so similar to humans, right? Right.

So that leaves us with two other – somewhat connected – possibilities. One is that like werewolves or vampires, grey aliens are a manifestation of deep-rooted racial memories, the fruit that ripens on the vine of our collective unconsciousness. The other possibility is that Greys are nothing more than a fad that got picked up and elaborated upon before taking on a life of its own, a meme from the decades before the word even existed. Before we make a call one way or the other, however, let’s take a look back at where the Greys came from.

For many ufologists and true believers, the answer to that question is a deadpanned “Zeta Reticuli.” Reason being is that, according to some string-and-bead-based model-making by an amateur astronomer, that is supposedly the origin of the aliens that allegedly abducted Barney and Betty Hill. Their story, which they claimed happened in 1961, became the first widely reported abduction incident, and featured a group of aliens that, while not totally in line with the contemporary conception of Greys, weren’t too far off either.

This particular abduction story kicked off a myriad of other similar claims, many of which, as you’ve probably guessed, featured small, grey humanoid aliens. The origins of the grey aliens stretch back far further than the 1960s, however, as H.G. Wells, in an 1893 article, described a futuristic evolution of mankind that was remarkably similar to Grey aliens. He picked up on the notion in a number of subsequent works which depicted the grey skin, big head, and large black eye-having creatures as being extra-terrestrial in origin.

Though Grey aliens can be spotted throughout pop culture – including Close Encounters of the Third Kind and even Star Wars – business really picked up during the 1980s. Reason being is that was the decade in which the Greys were first linked with one of the most famous alien conspiracy theories: The Roswell UFO incident. The claim was that the Roswell wreckage contained not only otherworldly technology but also the bodies of actual Grey aliens.

That rumor and belief spread unchecked throughout the 80s, during which time the Grey aliens became a crucial component of contemporary belief in UFOs. But in the 90s, the Grey aliens became even more central to the beliefs of not just amateur ufologists, but all manner of conspiracy theorists, due largely to the popularity of The X-Files.

The X-Files smashed together countless different conspiracy theories, tying the Grey aliens into a nefarious New World Order-esque organization. As one of the most popular television shows on the air, the show, and its depiction of Grey aliens, was enormously influential, leading to the conflation of Greys and pretty much every other wacky conspiracy theory or New Age belief you could possibly imagine. And given the type of people who go all in on such things, it shouldn’t come as any surprise that the Greys were latched onto by hordes of 90s ravers and drug culture adherents.

So, where does this leave us? There are a few different theories as to the origins of the Grey alien trope, including the idea that the creatures represent an idealized version of traits that read as “intelligent,” as well as claims that they line up with what a mother’s face might look like to the brain of a still developing infant. While there’s nothing to completely discount either theory, there’s also not a whole lot other than speculation and circumstantial evidence to support them.

And for what it’s worth, I’m inclined to believe that any theories to the deeper meaning of Grey aliens are a lot of malarkey. That’s because unlike say, werewolves and vampires—the belief in which goes back hundreds, if not thousands, of years—Grey aliens only really started popping up in the 20th century. If there was something baked into us to envision the little bastards, why didn’t they start showing up sooner? And why does their appearance seem largely limited to Europe and former European colonies?

Similarly, prior to Grey aliens really taking hold in the second half of the 20th century, there were other default looks for aliens. The most notable of these being the bug-eyed monster, a trope that was once the most popular way to depict an alien invader, showing up in countless movies and pulp magazines. There was even a more regional variation on the “standard” alien, the tall, statuesque, blond humanoids known as Nordic aliens, which were particularly popular in Europe during the 1950s.

So, while the Grey aliens certainly might seem, due to their ubiquity and frankly, excellent design, like some kind of vestigial memory from times long past, or the manifestation of some deep-rooted, primal fear, it seems more likely that they’re something just as powerful: A cliché.

Aubrey Sitterson is the creator of the sword & sorcery serial podcast, SKALD. There are no aliens in it, but if you think about it, in a way… we’re all aliens, right? It’s available on iTunes, Google Play, Stitcher & Podomatic. Follow him onTwitter or check out his website for more information.