When Facebook CEO Mark Zuckerberg hosted a livestreamed Q&A earlier this week, he was probably expecting questions about emergent tech and online entrepreneurism rather than someone asking whether he was, in fact, a shape-shifting alien reptile.

“Mark, are the allegations true that you’re secretly a lizard?” Zuckerberg read aloud, before replying in the negative and declaring the question “very silly”. Well, he would say that, wouldn’t he?

Zuckerberg is hardly the first prominent public figure to be fingered as a reptilian alien: everyone from George W Bush and Donald Rumsfeld to Simon Cowell and Kris Kristofferson (!) have faced similar accusations in recent years. As unlikely as it seems, the whole “reptoid” thing has become something of a meme in the internet age. But where did it come from?

That’s a surprisingly difficult question to answer. Aliens that combine human and animal forms have been a staple of pulp SF and comic books going back to at least the 1920s; as a staple of mythology, such hybrid figures can be traced back across millennia. And, yes, lizard-men have been spotted across the US from time to time, in places like Scape Ore Swamp, South Carolina, and Loveland, Ohio. What’s notable is their relatively late entry into UFO lore. There are a few isolated cases – the 1967 Seewalt close encounter in Canada, the 1978 Zanfretta abduction in Italy – featuring “lizard man”-type extra-terrestrials, but they are few and far between. Close encounter reports tend to focus initially on friendly Nordic “space brothers” and later on malevolent Greys: reptilians, along with weird robotic entities, shaggy giants and giant insectoids, remain outliers for much of the phenomenon’s history.

Mark Zuckerberg: when asked whether he was a reptile, he said the question was ‘very silly’. Photograph: Eric Risberg/AP

By the 1980s and 1990s, as the alien mythos darkened, there was some chatter about lizard-like ETs – some rescued from the Roswell saucer crash of 1947 – being kept at an underground military base at Dulce, New Mexico, and suggestions that these serpentine beings, not the spooky X-Files-style aliens, were the ones calling the shots. But the game-changer for scaly-skinned space beings appears to have emerged out of the pre-millennial tensions of the late-90s, when goalie turned sports commentator turned messiah David Icke published his book The Biggest Secret (1999).

Icke’s unlikely emergence as a key pundit of what might be called the Dark New Age rests on his bricolage-like methodology of pinching and recombining elements of all sorts of marginal discourses – occultism, UFOlogy, conspiracy theory, ancient astronaut lore, alternative history – into a tortuous grand narrative in which a sleepwalking, mind-controlled humanity is revealed to have fallen under the control of all-seeing evil overlords. On Planet Icke, these shadowy puppet-masters, usually known as the Illuminati, emerged as none other than shape-shifting reptoid aliens from another dimension with a taste for human flesh, preferably of the infant variety.

I have seen the Queen sacrifice people and eat their flesh … When she shape-shifts she has a long reptile face

It’s unclear how much of this stuff Icke actually invented – or how much he copped from a viewing of 1980s TV show V – but he seems to have drawn on various (and variously unhinged) sources, including self-confessed Illuminati slaves and “mind control victims” like Cathy O’Brien and Arizona Wilder. It was the latter who famously revealed that Queen Elizabeth II was not, in fact, human: “I have seen her sacrifice people and eat their flesh and drink their blood … When she shape-shifts she has a long reptile face, almost like a beak, and she’s an off-white colour…” And it wasn’t just Her Majesty: the rest of the royals were in on the act too, including the late Queen Mother, aka “Chief Toad”. It was inevitable, as time went by, that all sorts of other establishment figures, from politicians to pop stars, would be revealed as part of the grand conspiracy whose tentacles were found to reach into every aspect of human experience – even (perhaps especially?) Facebook.

The UFO phenomenon was once a strangely comforting one: close encounters revealed there was someone out there wiser than us, with a message of hope for cold-war humanity and some friendly advice about nuclear weapons. If, as Jung suggested, the UFO experience is largely one in which human hopes and fears are projected outward and read in the skies, then we should all be worried by its millennial transformation. The tangled web of intersecting conspiracies embodied in the reptilian meme suggests that, these days, we see ourselves as powerless victims of exploitation and predation by a self-perpetuating elite whose main concern is protecting its alien bloodline and keeping the rest of us in line ready for the ultimate sacrifice. Perhaps the only surprise is that the leave campaign hasn’t spotted the perfect metaphor for the EU here.