Human Extraterrestrials


Even though science fiction is often focused on the future, its assumptions are tied to the present.

Aldrin descends from Apollo 11In some respects this is obvious.  A story about the near future can become dated by history itself.  Every SF story prior to 1969 that describes the first moon landing in detail (happy 51st anniversary, last week!) is obsolete.  And every story that predicted a smooth reach out into colonizing the solar system directly after that first landing, unfortunately, is also defunct.  Stories can also be rendered unbelievable by scientific advance:  all the delightful tales based on a habitable Venus or Mars are gone with the, er, vacuum.

But there’s also a subtler way.  Even though F&SF specialize in examining our assumptions about the universe, the assumptions that seem plausible shift over time.  Fashions change.  To take a heartening example:  SF stories from the late 1940s and the 1950s tended to take it for granted that there would shortly be a nuclear world war.  (Hence it’s spot-on characterization when the 1955 version of Doc Brown in “Back to the Future” accepts Marty’s recorded appearance in a hazmat suit as logical because of the “fallout from the atomic wars.”)  But for over seventy years, we’ve managed to avoid that particular catastrophe.

One assumption that’s always intrigued me is whether we are likely to meet people like ourselves—and I mean, exactly like ourselves—on another planet.  If we discovered an Earthlike planet of another sun, might we climb down the ladder from our spaceship to shake hands with a biologically human alien?

Not Really Alien

I’m talking about a “convergent evolution” hypothesis—the notion that the human species might have developed independently more than once.  And, incidentally, the standard biological definition of “species” as “interfertile” (a more precise definition can be found on Wikipedia) is what I’m using here; because, obviously, one of the potential uses of the assumption in a story is to make possible a romance between two characters from different worlds, and romance is not unrelated to sex and reproduction.

The Cometeers coverSo we want to set aside, to begin with, a class of stories in which people from different planets are all human because they have a common ancestry.  For example, in Jack Williamson’s classic space opera The Cometeers (1936), Bob Star finds his true love Kay Nymidee among the human subjects of the decidedly nonhuman masters of an immense assemblage of space-traveling planets, the “comet.”  But the reason there are human beings present is that a research ship from Earth was captured by the Cometeers long ago, and these are the descendants of the crew.

It’s not uncommon for the inheritance to work the other way around.  David Weber’s “Mutineers’ Moon” (1991) starts with the eye-opening assumption that our Moon is actually a long-inert giant spaceship—and reveals that the humanity of Earth is descended from the original crew members of that spaceship.  Thus, it’s perfectly plausible when hero Colin MacIntyre falls for a preserved member of the original crew; they’re from the same stock.  Similarly, in at least the original 1978 version of Battlestar Galactica, the human survivors of the “rag-tag fugitive fleet” are human because Earth itself was one of their original colonies, which apparently fell out of touch.

The Era of Planetary Romance

In the early days of modern SF—say, from about 1912 through the 1930s—it was commonly assumed that the answer was yes:  human beings (with minor variations) might be found independently on other planets.  Arguably, this may have been because the early planetary romances—melodramas set on exotic worlds, heavy on adventure and love stories—were less interested in science than in plot devices.  But biology was less advanced in those days; recall that DNA was not identified as the basis of genetic inheritance until 1952.  It’s easy to forget how little we knew about things we take for granted today, even in relatively recent periods.

A classic early case is that of Edgar Rice BurroughsBarsoom.  In A Princess of Mars (1912), Earthman John Carter is transported by obscure means to Mars, called by its inhabitants “Barsoom.”  Those inhabitants include the nonhuman “Green Martians,” but also people identical to humans in several colors, particularly the “Red Martians” among whom Carter finds his lady-love, Dejah Thoris.  As a Red Martian, Dejah is human enough for Carter to mate with, and they have a son, Carthoris, thus meeting the “interfertile” criterion.

Lynn Collins as Dejah Thoris in John Carter of Mars

Lynn Collins as Dejah Thoris

To be sure, the biology here is a little mysterious.  Dejah looks entirely human, and even, to borrow a Heinlein phrase, “adequately mammalian” (see, for example, Lynn Collins’ portrayal in the loosely adapted movie John Carter (2012)).  But Martians don’t bear their young as Earth-humans do; they lay eggs, which then develop for ten years before hatching.  It’s not easy to imagine the genetics that could produce viable offspring from an individual whose genes direct live birth and one whose genes result in egg-laying.  But that didn’t stop Burroughs.

E.E. Smith, whose initial SF writing goes back just about as far as that of Burroughs, was willing to accept this trope as well.  In The Skylark of Space (published 1928, but written between 1915 and 1921), our intrepid heroes travel to a planet inhabited by two nations of essentially human people—although the double wedding in the story does not involve any interplanetary romances, but is between two pairs of characters from Earth.  Smith’s later Lensman series (1948-1954), which features one of the most diverse arrays of intelligent creatures in SF, also allows for apparently interfertile humans from a variety of planets.  My impression is that this sort of duplication was also true of some of the nonhuman species in the Lensman unverse—there might be, say, Velantian-types native to planets other than Velantia.

This approach wasn’t universal in old-time SF.  The more scientifically-minded John W. Campbell’s extraterrestrial character Torlos in Islands of Space (1930) was generally humanoid in form, but quite different in makeup:  his iron bones, for instance.  It’s been argued that a roughly humanoid form has some advantages for an intelligent species, and hence that we might find vaguely humanoid aliens on different planets—though this is pure speculation.  But “humanoid” is a far cry from biologically human.

Darkover Landfall coverWe see some persistence of this tradition into the second half of the twentieth century.   Marion Zimmer Bradley’s iconic planet Darkover, for instance (first novel published 1958), is populated by the descendants of Terran humans from a colony ship and also by the elf-like indigenous Chieri, who, despite minor differences like six fingers and golden eyes, not to mention the ability to change sex at will, have interbred with the Terran immigrants.

An interesting variation can be seen in Julian May’s Saga of Pliocene Exile (first story published in 1981).  When modern humans are sent on a one-way trip into the distant past, they are enslaved by the Tanu, aliens from another galaxy who have settled on Earth.  The story indicates that the Tanu were specifically searching for a place where the local gene pool was similar to theirs—which might also account for why they came all the way from another galaxy (also a somewhat antique trope) to get here.

It’s slightly odd that, even where basically identical human beings turn up on other planets, other animals never seem to be similarly duplicated.  On Burroughs’ Barsoom, one doesn’t ride horses, but thoats; is menaced not by tigers, but by banths; and keeps a calot, not a dog, as a pet.  In a planetary romance or science fantasy setting, one is less likely to see Terran-equivalent fauna than parallel creatures with exotic names and slight differences—whence the SF-writing gaffe “Call a Rabbit a Smeerp” (see TV Tropes and the Turkey City Lexicon).

At the Movies

The all-too-human trope is carried on into the present day in video media—movies and TV.  Again, this may be partly because the science is often subordinated to the plot; but the cost and difficulty of putting convincing nonhuman characters on-screen is surely another factor.  Filmmakers’ ability to depict exotic creatures, however, has changed immensely in the last forty years, to a point where almost any imaginable creature can be created if the budget is sufficient.  Thus, the original Star Trek series of the 1960s stuck largely to slightly disguised humanoid aliens, perhaps relying on the ‘universal humanoid’ hypothesis mentioned above, while later series were able to branch out a bit.  Similarly, the Star Wars movies could readily give us nonhuman characters like Jabba the Hutt, Chewbacca, and C3PO; they, too, grew in variety as the capabilities of CGI and other techniques expanded.

Jupiter Ascending movie posterStill, it may be harder for us to adjust to interactions among characters where we can see their nonhumanity, rather than just reading about it.  So we still tend to see extraterrestrial humans on-screen.  The Kree in Captain Marvel (2019), for example, are indistinguishable from humans—an actual plot point, since this makes it possible for Yon-Rogg to tell Carol that she’s an enhanced Kree rather than a kidnapped human.  The Kree do have blue blood, in the movie; it’s not clear what kind of biological difference (hemocyanin?) might result in that feature.  We also see a number of alien humans in Jupiter Ascending (2015), though I think of that tale as a deliberate throwback to pulpish science fantasy or planetary romance.

A Match Made in Space, fictional coverI keep wanting to cite the fictional novel written by George McFly as shown in the closing scenes of Back to the Future, “A Match Made in Space,” since the cover seems to suggest an interplanetary romance (and one thinks of George as a nerdy romantic); but it isn’t actually clear whether that’s the case.  All we have to go on is the title and the cover, and that could just as easily depict a match between two humans, fostered by an alien matchmaker (or vice versa).

The Modern Era

We don’t see nearly as many extraterrestrial humans in modern SF, and for good reason.

The more we understand about genetics, the less likely it seems that another human species, so closely similar as to be interfertile, could evolve independently.  What we know about evolution suggests that there are just too many random chances along the way—cases where the prevailing mutations might have turned out differently.  Even if we assume that humanoid form is probable, why not have six fingers, or hemocyanin rather than hemoglobin?  While I’m not well enough educated in biology to venture any actual probabilities, I think our growing sense of the complexity of the human body and its workings, over the last seventy years or so, has simply made it seem vanishingly unlikely that an independently evolved intelligence would come out that close to the human genotype.

For example, the scientifically-minded Arthur C. Clarke depicted a galaxy in which each intelligent species, including humans, was unique:  The City and the Stars (1956, developed from an earlier story published in 1948).  In one of the unused story fragments he wrote while working on 2001:  A Space Odyssey (1968), his hero, well along on his journey into mystery, thinks:

He did not hesitate to call them people, though by the standards of Earth they would have seemed incredibly alien.  But already, his standards were not those of Earth; he had seen too much, and realized by now that only a few times in the whole history of the Universe could the fall of the genetic dice have produced a duplicate of Man.  The suspicion was rapidly growing in his mind—or had something put it there?—that he had been sent to this place because these creatures were as close an approximation as could readily be found to Homo sapiens, both in appearance and in culture.  (Clarke, The Lost Worlds of 2001, ch. 39, p. 220)

Contemporary SF writers who are really adept at building interesting and coherent aliens—David Brin and Becky Chambers, to name two of the best—give us a wide range of wildly exotic creatures from other planets, but not humans.

The Uplift War, coverIf we are still fond of the idea of interplanetary romance, we might find a possible work-around in the shapeshifter.  The Tymbrimi female Athaclena in Brin’s The Uplift War (1987) uses her species’ unusual abilities to adjust her appearance closer to that of a human female—but of course she has an entirely different genetic heritage, as that ability itself demonstrates.  The result wouldn’t meet our criterion of interfertility, no matter how close the similarity in physical structure.  To adjust one’s genes in the same way would be another order of change altogether.

Starman movie posterThe 1984 movie Starman, in a way, plays off this idea.  The alien in this case is apparently an entity made of pure energy, without a physical structure of its own.  Using hair from the female lead’s deceased husband, it creates a new body with a human genetic structure.  The two do, eventually, prove to be interfertile.  If we’re willing to accept the notion of an energy being in the first place, this approach is actually more plausible than, say, mating with the oviparous Dejah Thoris.

If one were writing a SF story today, it would be rash to assume that Earthborn characters could run across independently evolved humans elsewhere.  The idea may not be entirely inconceivable.  But it’s out of fashion for good reasons.  Attractive as the notion of interplanetary romance may be, at this point we’d best confine it to the kind of case noted above, where some common ancestry—no matter how far-fetched—can account for the common humanity.

12 thoughts on “Human Extraterrestrials

  1. The most recent plausible explanation I’ve seen is panspermia – the ultimate source of life coming from space to a number of similar planets, thus begetting creatures of similar biology.

    But I too find the whole idea too unlikely. It’s one of the reasons why I write parallel worlds stories so much instead.


  2. This blog often reveals to us glimpses into the mysteries of life, the universe, and everything. Today’s mystery: how does one nurse an egg? 😉

    Back to some more serious takes — one of my favorite characters in the series Farscape was the toad guy, Dominar Rygel XVI. Most of the show’s aliens were rubber forehead humans — and often, they even dispensed with the rubber foreheads — but it seemed a nice flight of fancy to have a couple less humanoid examples too, such as a very dastardly, loosely amphibian-like scoundrel, or a sentient ship.

    But, speaking of the ship, she rarely was a character herself, if ever. She was involved in the story as an instrument (Moya is a ship, after all), or her thoughts and feelings would be related via (and thus, might as well have originated from) the more approximately humanoid Pilot. In another series, Andromeda is the ship’s avatar, and she is also suitably mammalian. The casting choices in series such as Andromeda were surely guided by fan-service, nudge nudge, but it seems the necessity for a human avatar came from somewhere else.

    I don’t think I’ve seen any series where one of the characters in the protag ensemble is Cthulhu. I’m not sure it’s even possible. Cthulhu and the like work as incomprehensible presences; place them in the team we’re following and … at some point we have to see a face in that cloud, a spark of ambition or fear or vulnerability. Get exposed to a character long enough, and they have to be humanized, either by the audience groping in the dark, or by the authors explicitly to avoid there being not much for the audience to hang empathy on.

    Cthulhu is a bad example because the whole point of Lovecraft’s Old Ones is, these are cosmic horrors one has no business empathizing with.

    But there’s an underlying question there. Has any long work tried to show us a character that is truly alien, and the point of the arc is really us (via the protags) coming to understand this creature? Bonus points if the understanding remains “through a glass darkly”: it should be clear, even as the humans start thinking they understand, that they also know they understand even less than they would another human, that though they can reliably see the same face in that cloud of possible interpretations, they are aware it’s mostly them seeing the face than the cloud conforming to it.

    Arguably, something like Arrival might attempt to do this, but I think alienness of this sort is more easily tolerable in a short form such as a movie. We still don’t empathize with the Arrival aliens, after all. Hence why my curiosity is about a longer piece of fiction.



    • Interesting!

      The ship as a character — I’m taking on that one in my next story. 🙂

      I agree about the Old Ones. If we tried to write a story from the viewpoint of a cosmic horror — or even a cosmic wonder — we, or the reader, would have to assume the mind-set of a being that, by hypothesis, we can’t comprehend. Can’t be done.

      What *could* be done is what your next paragraph proposes: show the alien character from the inside and then have humans gradually learn to understand it. That would be a pretty extensive task, and thus, as you say, more suited to a long-form story. First we’d have to present the alien in enough depth that the reader *could* come to understand them; and then we’d have to show the gradual growth in understanding of the human characters — which, as you observe, might never be complete.

      David Brin arguably pulls this off, to at least some degree. The neo-dolphins in _Startide Rising_, the Tymbrimi in _The Uplift War_, some of the really exotic species like the Traeki in _Brightness Reef_ — we do see them from the inside, and we see humans trying to comprehend them and sometimes failing. But there are a lot of human characters in the story too, and in most cases the humans and the nonhumans have lived together long enough that they’ve already scoped out the areas of common understanding and of mystery.

      There’s a sort of analogue in stories where the viewpoint character is human, but thinks quite differently — on the autism spectrum, for example. I’m thinking of the first part of Sturgeon’s _More Than Human_ or Roger Levy’s _The Rig_.

      I feel sure there are long-form stories that better fit your description than any of these scattershot examples, but I can’t bring one to mind. Anybody else think of an example?


      • Frank Herbert’s Whipping Star – it’s a difficult read (I’ve never tried to reread it), but fascinating. Humans come in ?radio? contact with an alien being, and spend pretty much the entire novel just trying to communicate with it. Alien indeed!

        CJ Cherryh likes to mine similar ore; a couple of her more accessible ones are The Pride of Chanur, where, by the time the leonine aliens meet the human, the human feels like the alien. Another is Cuckoo’s Egg, where an alien is raising a human infant for mysterious reasons, and we learn about that alien as the story progresses.

        Liked by 1 person

      • I’ve heard of the Herbert, but don’t think I’ve ever read it. Similarly with the Cherryh — I’m deplorably underread in her work. I may have to hunt that one down.


  3. Right! Darn, I meant to say something about panspermia, but forgot.

    I agree with you. I’m willing to buy organic molecules traveling across space in, say, meteors (though if that weren’t a real thing I’d have considered it pretty implausible too!); or even the notion that an amino acid or RNA fragment or something might “seed” a general pattern for life on the new world (right- or left-handed stereoisomers, for example). But you’d never get something as complex and specific as the human genome that way.


    • There was I think a Star Trek the Next Generation episode where evidence was found of a forerunner race, that seeded Earth, Vulcan, etc. with what eventually became human, Vulcans, Klingons, etc., and that’s why they could interbreed.

      A more plausible concept than panspermia, but it tends to hijack the narrative. Wouldn’t anyone want to know more about their ultimate progenitors? If I introduced something like that, I would feel obliged to ditch my existing storyline(s) and follow that one.

      Thanks for an even more discussion-worthy post than usual.


  4. Yes. That’s about the only plausible way to do it, I think. Andre Norton had her Forerunners, and don’t LeGuin’s Hainish stories incorporate a similar idea?

    I considered using that concept myself, but decided against it, one of the reasons being just what you point out: it hijacks the narrative. The quest for the Originals quickly becomes a more fascinating storyline than whatever we were using it as background for.

    And thank you for joining in!


    • Well, there was a franchise that was doing that Originals story — Prometheus!

      I deliberately didn’t say Alien there. I think it would have been a lot, lot better if Prometheus was either the competent Space Horror, Alien prequel John Spaihts originally intended, OR its own, completely independent story line about how/why the Originals decided to off us.

      Prometheus has been getting a lot of flak for some reason. It is flawed, but endlessly fascinating. I started writing by writing fanfic for it, and it will always have a warm place in my heart.

      Too bad they made no sequels. I repeat. They made no sequels. None.



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