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This is discussion archived from a time before the current discussion method was installed.

From YKTTW

Icalasari: Why is HSOWA on here? Pokemon have been confirmed or have evidence pointing to them all being subspecies. In at least one manga, it is said that they are all genetic variations of the same species. In the main games, Mew is the ancestor of all Pokemon, bar Dialga, Palkia, Giratina, the Pixies, and Arceus, and has the DNA of all of those Pokemon, which hints at them all being related, with certain gene expressions not being compatible with each other (hence why Milotic can't breed with, say, Smeargle). It is a case where it is justified, and even with it being justified, there are still barriers. Not good ones mind you (I think female Skitty have to bathe in Wailords, erm, yeah, in order to keep from getting crushed), but barriers none the less


Nate The Great: As a Hitchhiker's Guide freak, I'm pretty sure that Swedish Meatballs never come up. I think somebody got Hitchhiker's mixed up with Babylon 5. Could somebody verify and make the change?
  • Confirmed and changed. This is one of G'kar's trademark "cute moments."

Mister Six: I know I'm going to seem like an ultra-mega-nerd (well, I am, but I don't want to seem like one) but "this does not account for how it is able to recognise an alien creature with a previously unencountered biochemical makeup as a suitable host" — isn't the point that it can use any kind of warm-blooded creature as a host?

Tulling: The point is that it is extremely unlikely that it would have such an ability either through evolution or design. It may be able to recognise a creature as warm-blooded by sensing the heat it emanates, but how could it possibly adapt itself to a previously unencountered species "on the fly"? It shouldn't, for much the same reason that livestock diseases usually do no cross over to humans. This goes double when you consider the "biosphere barrier". Now, if it had been designed to target humans in particular or terrestrial species in general, it would be a different matter.

Mister Six: "how could it possibly adapt itself to a previously unencountered species "on the fly"?" - are you talking about the incubation process here? Or the hunting process?

Tulling: The impregnation and incubation. It does it seemingly with no difficulty at all, like it was specifically designed to infest humans.

Mister Six: Well, the impregnation itself is just a case of shoving the facehugger's tube into an orifice. It could presumably do that to anything with a breathing hole (like the candiru fish can swim up a urine stream and suck blood out of a penis just as easily as it can swim into a fish's gills like it's actually supposed to).

As for the incubation - through whatever process, it just happens to absorb and incorporate DNA. It does it with similar ease to a dog. As this is clearly nonsense science, I don't see why the process would be any harder with a human or a dog than it would be with whatever alien species it originally lived with. Perhaps there are some species that would die if the facehugger tried to lay an egg in it, or whose DNA would not be compatible with the aliens', but obviously we don't see them because that would be a boring movie. If that's the case, we're just unlucky enough to fall within its DNA band. It's a crap shoot and we rolled snake eyes.

Granted, the DNA absorbtion thing is scientifically nonsense, but for that very reason (ie, it's so beyond human understanding as to be fantasy) I don't see why that process ought to be harder with an alien species than ones that lived on a planet with it. It absorbs DNA. That's what it does. Why would that be harder from a soft, squishy human than from the hard carapace of the dead alien pilot from the first movie?

Tulling: True, but this article is all about pointing out the unlikelyhood of such a creature actually existing given our current understanding of biology. That the Alien universe works like this means that it is Science Fantasy to the same degree any fiction featuring half-human hybrids is.

Mister Six: But your objection on the page isn't about the impossibility of the DNA transfer as a principle, it's about the alien 'knowing' that humans are suitable for incubation, when by the looks of things anything with a pulse is suitable for incubation. Remember, this is Serious Business. I'll do a rewrite later.

Tulling: You are right, I did not express what I had intended properly. It was late and I could not sleep.

Seth: There is also traumatic insemination to account for, plenty of terrestrial insects impregnate females by piercing them and injecting. It's possible that the facehuggers could have that capacity as well. Meaning that we are lucky to have a less traumatic option :p.

I always took the placing eggs in people as "warm being - big hole on top - place eggs inside" again plenty of terrestrial insects can do just that. Placing eggs in the carcass of a cow or into a gash in a humans head just as easily, it's just looking for incubation and it's not a massive leap to suggest that it is so far evolved that it can adapt to many environments for said incubation.

Ununnilium: Yeah; it really doesn't seem like it would need a specific species to nest in. I'm thinking of pulling that one.

Licky Lindsay: how about that fact that species from different planets are usually able to breath the same air? Even if you assumed that everybody breathes oxygen and exhales carbon dioxide, wouldn't you think that the mix of different elements in the air on the Enterprise might be all out of whack for Worf's lungs?

Seth: I assume that as long as the air is breathable, comfort is of little consequence. People (And therefore Rubber-Forehead Aliens) can adapt to different climates on earth with enough ease, it would be a fair enough handwave to say that they simply all adapt to the strange mix of air. So long as it has enough O2 for the humans, CO2 for the Plant Aliens and Nitrogen for the Bizarre Alien Biology creature.

HeartBurn Kid: Isn't the War of the Worlds thing a bit of a subversion? After all, even though it does show the Martians as being susceptible to the same types of microbes as humans, it specifically makes the point that they are more susceptible to them from coming off-world; not having the benefit of having evolved alongside them, and thus having developed some degree of immunity to them, even the mildest pathogens could destroy them utterly.

Tulling: My understanding of biology is perhaps too limited, but it would seem similar to a disease crossing over from one species to another, only with the added difficulty of adapting to an extraterrestrial biological make-up. Ie the microbe would not "know" how to attack the bodies of the Martians.

Nezumi: Basically, it'd be very, very hard for a disease to cross such a wide species gap, bordering on impossible. But if it did, this could be very dangerous—the other species would, indeed, have no natural resistances and immunities... and the same biological differences that make it difficult for the disease to cross could make it even worse in the other species—or, alternately, on the plus side, they could make it less severe. This isn't conjecture—we've seen real-life examples, albeit not on the extraterrestrial level.

Nezumi: Since it's better to actually provide examples, rather than say they exist, I've decided to add to this. Probably the most dramatic example is HIV/AIDS. It's believed to have originated from chimpanzees to whom it was only a nuisance. Somewhere along the way of adapting to affect humans, its coping with the (comparatively small) biochemical barrier also inadvertantly made it a deadly plague that almost completely disables the immune system, leading to death from things as simple as cold. And, as discussed in the main entry, the effects diseases can have on a population newly introduced to them, with no resistances or immunities, can be devastating, as has happened when European civilization encountered native populations.

Milly: Would the illithid (from D&D) process of reproduction (sticking a tadpole into a human's head, letting it eat the brain and hijack the body's systems in order to shape the body into that of an illithid's) be considered part of any of this? It seems to be designed purely for humans, as sticking the tadpoles into other species does create half-illithids (IE: those who do not metamorphosize as well, ending up merely a few tentacles around the mouth and some psionic ability)?

Kizor: It might, it definitely goes into Face Full of Alien Wing-Wong.

Ununnilium: I say no, because it's fantasy. A Wizard Did It.

MrAstroPhysics On the topic of atmospheres, it is extremely unlikely that non-oxygen breathing macro-organisms (i.e., not bacteria) exist. The reasons for this are as follows:

First and foremost, molecular oxygen is a highly reactive substance that does not occur in nature. It is exactly this highly reactive nature that allows both plants (plants use oxygen as well) and animals to use oxygen as a fuel for chemical reactions.

Molecular oxygen is distinctly unique among gases because it allows a very wide variety of reactions and is a powerful reactant with almost all compounds involving the most common elements in the universe (Hydrogen, Carbon, Nitrogen, Sulfur — Helium is common but essentially inert.)

Biological systems involving respiration of other gases such as methane, molecular nitrogen (N2) or CO 2 are best described as novel ideas not practical in chemistry as these gases have little reactant potential (except with O2, of course). And molecular fluorine/molecular chlorine, the only gases with similar reactivity do not offer a large variety of different reactions and therefore are not a fit with complicated biological processes.

Considering the present understanding of biology (even with ideas involving comets) and the need for a powerful solvent, a role that only water or ammonia can perform for different reasons, the only viable reduction/oxidation reaction that can store/release energy (such as how earth like stores energy in sugars) is going to produce oxygen as a byproduct as molecular nitrogen (N2) is virtually chemically inert and cannot be involved in a reversible chemical reaction in a system that stores energy for later consumption — a prerequisite for macro-organisms.

Ununnilium: Meh. It's unlikely, but certainly not impossible, meaning that it's not really worth mentioning in the entry.

Sci Vo: It looked like there were more aversions there than actual examples, but it turned out that all I had to do for most of them was just take out the claims that they were aversions, and all of a sudden they magically became good examples.

Ununnilium: Taking out "To say nothing of the differences in psychology which would likely render humans and any aliens that might be encountered utterly incomprehensible to one another" because, first of all, it doesn't apply to this trope, which is all about physical differences, and second of all, we really can't say how similar nonhuman minds would be to ours.


Einar: I'm removing this bit (and its reply) because it's just plain wrong.

  • And then pretty much thrown away because the Ringworld is full of humans, or, at best, Rubber-Forehead Aliens for no explained reason, and none of the protagonists of various human and alien species have any problem there whatsoever. Oh, and Niven makes luck inheritable. Niven Did Not Do The Research on biology, and one single throwaway line doesn't fix that.
    • This one is actually justified. Humans are actually descended from the same ancient alien race that built the Ringworld as a safe home for their non-sentient breeders.
    • (my addendum: And as for the other species, they are all capable of living in more or less the same planetary conditions because they were mostly descended from the food algae of a Predecessor-type race that lived on Earthlike planets (except for the Bandersnatchii). The Ringworld builders put them all there for observation.

The issue of making luck heritable belongs somewhere else, and honestly I don't think it requires too much suspension of disbelief.

Kendra Kirai: I don't want to make a point of this in the main article (Yet), but really, the respiratory system is quite adaptable. Humans can breathe pure oxygen, for instance, though it's not recommended for extended periods. We can survive in pressures and oxygen concentrations that are extremely low, with only occasional puffs of supplemental air...and the atmosphere even on earth changes it's trace elements depending on where you are and which way the wind is blowing at the moment. It's not too far beyond the realm of possibility that there's a mix of oxygen/nitrogen/trace elements that is suitable for a healthy chunk of alien life from an M-class (Earth-like) world. It'd take some time for everyone involved to get used to it, but once they are... Think of it like moving from New Orleans to one of those big mountains in Peru. You're going from below sea-level (higher pressure) to a far lower pressure, and far thinner air..it'll take some time to acclimate, but once you do, you're fine.

Oh, and about the Xenomorphs from Aliens...I believe they actually implant eggs in their host, which takes nutrients and DNA from the host, akin to pregnancy...of course, they then grow really damn quick, and seldom seem to eat their host's carcass to gain mass before they grow into the eight-foot-tall black-carapaced Aliens we know and...know. Gotta wonder about that.
Question:Technically wouldn't tropes like Mars needs Women and other alien romance things be subtropes of this?

Bob! Probably.
Bob!: Cutting a non-example. In the episode in question, the virus was only spread between humans.

  • Used straight in another episode, where the team (and most of the SGC) gets infected with a disease that basically turns them into Neanderthals.

Novium: Ditto. Stargate often does things that falls under this trope, but examples of human beings catching diseases they haven't previously been exposed to from other human beings hardly applies.

  • Used straight in Stargate Atlantis, where a strain of a common childhood illness in the Pegasus Galaxy has nearly disastrous results for the Atlantis personnel from the Milky Way.

Cynthia Wakefield: In case anybody questions this: Humans and Syreen are the same species, as they are interfertile. Shofixti live and work aboard the Human Starbase. No mention is made of any special accommodations (while accommodations ARE mentioned for other races that do so, like the Orz). Humans, Syreen, and Shofixti thus share an atmosphere type. Yehat and Pkunk are from the same planet, ergo same atmosphere even if the Pkunk have speciated. Yehat and Pkunk thus share an atmosphere type. A Shofixti boards a Yehat ship and the species have had very frequent contact, but this does not mean that one or the other species wasn't using respirators. Ditto Utwig and Supox, though I'm not sure the Supox "breathe" per se. May or may not be any transitive property here.

As for one race working aboard another's ships — it's specifically mentioned that an alien ship only requires an alien pilot. Virtually all crew (in II, at least) are either Human or Shofixti. It's possible, particularly since Fwiffo specifically says that the Humans are reverse-engineering the alien ships, that an "Orz" ship in your fleet is actually a Human ship made with Orz technology and only the captain's cabin is a water-breathing environment.

If we accept Star Control III as continuity, we could probably get exact atmospheres and conditions for every race that appears in that game by examining which planets are ideal for each race. I seem to remember, though, that the results ended up contradicting not merely II but also itself — Syreen and Humans had different ideal worlds, Vux and Vyro-Ingo had different ideal worlds, the Mycon wanted rocky worlds, the Ortog-inhabiting Xchaggers didn't want the same worlds as the Ortog-raising Humans, and so on.


Travis Wells: I pulled this from the Star Trek entry in the cross-species disease section:
  • Deep Space Nine had a disease that specifically targeted Changelings, though it was engineered.

That's not an example, or important enough an aversion to be included. It was a single-race disease, it never spread.

Triple Elation: What kind of a trope is this? Some 80% of the examples are aversions.