Planet Earth might be home sweet home, but is it really humanity's birthplace? We explore science fiction stories where humans come from everywhere but Earth, be it by colonization, alien experiments, or good old-fashioned panspermia.
Panspermia is the term for the most scientifically plausible version of this concept, but it isn't necessarily what science fiction usually presents. The panspermia hypothesis holds that the building blocks of life are not found exclusively on planetary bodies but are instead found scattered throughout the cosmos, and it is these spaceborne particles that are at least partly responsible for life on Earth. There's a little circumstantial evidence for the theory (although far, far more to support the reliable old "Life comes from Earth" hypothesis), and there is something undeniably fascinating about the subtext – the aliens are already here, and we are they. But science fiction barely ever depicts the actual theory of panspermia, mostly because it's just a physical process that takes billions of years to play out and is pretty boring unless you're willing to get really mystical.
What science fiction more properly deals with is exogenesis, which simply states that humanity or its genetic ancestors didn't always live on Earth. That generally means one of two things – either an ancient alien race introduced life to a previously dead Earth (sometimes as part of a larger directed panspermia project) or a bunch of humans from some other civilization colonized Earth, a fact that somehow slipped the minds of their descendants (you know…us). Plenty of science fiction deals with both, including two of the big science fictions works currently in the news. (The occasional spoiler may lie ahead.)
Outlander
One of the most satisfying little details of everybody's favorite Vikings vs. aliens epic is its answer to why Jim Caviezel's character, the alien Kainan, looks exactly like the Norsemen and how he can possibly speak their language.Outlander solves both of these problems by revealing Earth is an "abandoned seed colony" of Kainan's spacefaring civilization. Unfortunately, the whole notion that Earth was colonized by an interstellar race really opens up a far bigger plot hole than the one it was meant to fill. After all, Kainan's people would have had to have "seeded" Earth eons ago. If they could pull off planetary engineering on that sort of scale way back then, you'd think they wouldn't have so much trouble with a bunch of bioluminescent dragons. In the end, it's probably best not to think too much about the logistics of the whole abandoned seed colony concept. Because, ultimately, the very inclusion of the idea in the first place is, like so much of Outlander, awesome.
Battlestar Galactica
In both the original and new versions of the series, humans originally came from Kobol, the legendary planet of the gods, and Earth is just the fabled lost colony. The new series is busy dealing with Earth, so it's entirely possible a couple "What the frak?" moments still lie ahead that will reveal humanity actually did come from Earth. The original series, however, left no doubt that Kobol was where we all came from, as the no-budget god-awfulness that is Galactica 1980 established contact between the Galactica and contemporary Earth. Flying motorcycle chases ensued.
Star Trek
The Next Generation episode "The Chase" sought to acknowledge and explain the genetic improbability of a galaxy full of nothing but humanoid aliens with rubber foreheads. The solution – ancient aliens who, upon finding themselves all alone in the galaxy, seeded various planets with their genetic codes – is surprisingly deft, and actually turns a three-decade failure of imaginations and budgets into something almost elegaic. As one would expect, Picard takes this existence-altering revelation in his usual stride, while the Cardassians look a bit grumpy.
Stargate
Honestly, between all the genetic engineering, forced relocations of ancient humans, and universe-altering civil wars between godlike aliens it all gets a bit difficult to keep track of which species actually came from where. In short, a bunch of plague-decimated demigods maybe used this thing called the Dakara superweapon millions of year ago to shoot their genetic information throughout the Milky Way, which maybe had something to do with humanity's evolution. Or maybe not.
Babylon 5
Since we might as well finish off the sweep of nineties science fiction, the Centauri initially tried to dismiss Earth as one of their lost colonies. Sure, this probably wasn't true, but how else are you going to haze the new interstellar species?
Isaac Asimov
Most aliens seem to create life on Earth for slightly more practical (well, relatively speaking) reasons than the Star Trek aliens' "monument to our existence." Asimov imagined Earth as an eons-old alien experiment not once but twice – in "Jokester", the aliens did it to explore the concept of humor, while in "Breeds there a Man…?" the aliens are engaged in a more vague exercise in genetics. There's also "Death Sentence", where an anthropologist for the Galactic Federation discovers that a previous civilization created a planet of robots as part of a larger psychological experiment. Realizing the Federation will surely have to destroy the planet as a potential threat, he decides to take his dire warning to one of the robots' biggest cities: New York.
Wildstorm Comics
The Kherubim people sent their genetic seed throughout the universe in a bid to conquer the universe without their genetic descendants even knowing it, which they then followed up by actually conquering much of the universe.
Ringworld, by Larry Niven
It turns out we're all part of a larger plan by the Pak race to create a galaxy full of ultra-lethal, ultra-intelligent superhumans. Apparently, the plan failed because there wasn't enough of the right kind of fruit.
Mission to Mars
In this Brian de Palma stinker, a bunch of Martians that didn't flee their dying planet shot the neighboring Earth – then a barren chunk of rock – full of the building blocks of life because…um, because they wanted to take Gary Sinise on a tour of the universe? (And that was probably the least nonsensical part of that movie.)
Salvage Rites, by Eric Brown
One of the very few times when a race made from directed panspermia confronts their creators, this short story finds a group of Benedictine monks in a cathedral-shaped starship seeking out what is, for all intents and purposes, God.
South Park
In easily the most awesome use of the concept, the anniversary episode "Canceled" revealed Earth for what it really is – one giant reality show. At least in South Park, someone is actually bothering to watch.
Starliner, by David Drake
In this 1992 novel, the narrator explains that no one bats an eyelid at botanists cross-breeding plants from different worlds because panspermia is "no longer a hypothesis but simple observation." Not the most earth-shattering application of panspermia, but still.
Ej-es by Nancy Kress
A rather less mundane spin on that same idea, as members of an interstellar marine corps realize a deadly plague on one planet threatens all the intelligent species in the universe – because panspermia makes them all genetically related.
Doctor Who
The classic "City of Death" features a more accidental case of aliens creating life on Earth. In the midst of all the ridiculously complex art forgery, random acts of violence, Monty Python cameos, and endless location shots that prove the thing really was shot in Paris, writer Douglas Adams somehow squeezes in the origin of all life on Earth. As it turns out, an exploding Jaggaroth ship kickstarted the whole "life" thing. That was nice of them.
The Hitchhiker's Guide to the Galaxy, by Douglas Adams
Speaking of Douglas Adams, his most famous work envisions the noblest version of the alien-built Earth. Indeed, the emphasis here is on "built", as Earth is not a planet at all but instead a ten million year old computer program supervised by hyper-dimensional mice designed to determine the question to life, the universe, and everything. Of course, as is so often the case, this wondrous philosophical pursuit was interrupted by a bunch of hairdressers, TV producers, and telephone sanitizers from the planet Golgafrincham, who obliviously managed to replace the native humans and almost wreck the entire program. All of which rather neatly leads us back to wandering, forgetful colonists.
The Hainish Cycle, by Ursula K. Le Guin
In ancient times, colonizers from the planet Hain came to Earth and, for a time, coexisted with its native hominids. Whether the settlers ultimately killed the native Earthlings or simply bred them out of existence is anybody's guess, but the Hainish now consider modern humans their descendants.
Women of the Prehistoric Planet
This MST3K entry builds a whole parable of post-War American-Japanese relations around two rival alien races, time dilation, and giant iguanas, with plenty of sixties-era chauvinism left to go around. After a whole lot of silliness (as that previous sentence probably suggested) the marooned lovers Tang and Linda settle down on the titular prehistoric planet, which they decide to call…well, I think you can guess, but it rhymes with "Mirth."
Earthsearch
The classic BBC radio series had one of the best twists on this idea, as the four teenaged survivors of the massive starship Challenger search for Earth-like planets to colonize. It's slowly revealed that the planet they call Earth has some rather unrecognizable geography, but that the Earth-like planet they finally do discover, with its saltwater oceans covering two-thirds of the planet, sounds very familiar.
The Twilight Zone
But stories don't get much more familiar than the 1963 episode "Probe 7, Over and Out." Astronaut Adam Cook finds himself stranded on a faraway planet just as nuclear war is breaking out back home. He encounters Eve Norda, an alien who cannot understand his language. The pair ultimately agrees to start a new life together on the planet that Eve keeps calling "Irth." Judging by their first names, I'm guessing they'll do just fine.