I'm looking to devise an extraterrestrial parasitic organism that perpetuates itself by infecting entire stellar biospheres before moving on to colonize other inhabited star systems. This organism would be a very well adapted interstellar apex predator.

The concept is inspired by the Halo franchise's "Flood" species, but is intended to be much more fleshed out and within the realm of hard science fiction.

The parasite seizes control of the body of a host and utilizes every means and resource at its disposal to make the host a maximally-efficient vector for transmitting the pathogen to other potential hosts. This includes hijacking the host's nervous system to influence its behaviors (similar to what Cordyceps does), and converting the host's natural cells into the parasite's dynamic cells, giving the parasite the ability to cause the host to undergo massive anatomical/physiological transformations (sometimes very rapidly).

Hosts will be able to communicate using pheromones to coordinate group action and inform the parasite how to behave at different stages of the epidemic (e.g.: not to make itself too obvious at first until it has a strong foothold over the population, etc.), making them an effective swarm intelligence.

Eventually, when enough of a sentient population has been subjugated, many sentient hosts should converge to form a gestalt, group mind "brain", capable of applying higher reasoning and tactics to its cause of infecting as much as possible with maximum efficiency. At this point, the groupmind and all of the hosts within its range effectively become a superorganism. The groupmind would broadcast its directions to the infected population telepathically (using the EM method depicted on this thread, which brings me to question #3 in my list below).

When everything in the groupmind's reach (typically a star system) has been completely subjugated, assuming the groupmind has achieved sapience and has the resources of a fallen interplanetary civilization at its disposal, it would then devise a way to colonize as many other star systems as possible (with priority on the star systems that seem likely to have life, particularly sapient life).

I'm looking to maximize the virulence of the parasite, as well as the plausibility of the concept.

It must be able to exist within a hard science fiction setting: no FTL travel, humanity is confined to the Solar System (and for the most part, just Earth). I've considered the fact that the lack of FTL travel is a hindrance on the parasite's ability to jump between star systems (given that it can't just hitch a ride on an FTL ship), but it could hitch a ride on a sub-light speed ship.

My questions/problems are:

  1. What should the infectious agent be (e.g.: bacteria, fungus, virus)? Would the copious amount of DNA that such a well-adapted creature would require fit inside of the infectious agent?
  2. Flesh out the mechanisms behind the parasite's functions, including its neurological hijacking ability and its ability to rapidly transform a hosts body. Point out any specific obstacles and/or physical impossibilities with these processes you can identify.
  3. Would the parasite be able to acquire and integrate enough metal into its host's nervous systems (or even the nervous systems of only certain hosts, such as locational nodes) to facilitate telepathy? If not, are there any other ways to create centralized groupmind? If not, are there alternatives to this groupmind?
  4. How should the groupmind's colonization protocol work to maximize the likelihood of landing in a star system inhabited by a sapient, spacefaring civilization that its offspring will then be able to launch its own colonization effort from?
  5. Any issues with what I've described above?
  6. How might such a species evolve?
  • $\begingroup$ I like your idea but this question covers a ton of bases, making it very broad - it may be more appropriate to break down each of those 5 questions into - well, separate questions. $\endgroup$
    – Zxyrra
    Jan 3, 2017 at 2:36
  • $\begingroup$ I understand it's a little broad, but it's a whole discrete idea. If I broke this question down into smaller questions, the answers to individual questions wouldn't be cohesive with each other. $\endgroup$ Jan 3, 2017 at 16:36
  • $\begingroup$ fair point, agreed $\endgroup$
    – Zxyrra
    Jan 3, 2017 at 21:23
  • $\begingroup$ I would specifically separate out the question about telepathy and incorporating metal since that can be answered independently from the rest. $\endgroup$
    – Tim B
    Jan 4, 2017 at 13:11
  • $\begingroup$ I understand that but there is already a whole forum thread about EM telepathy. I'm just wondering how such a system might be integrated into this specific theoretical organism taking all of the other answer-determined factors (pathogen type, etc.) into account. :) $\endgroup$ Jan 5, 2017 at 2:44

6 Answers 6


This is a really excellent idea. One that is quite thought provoking - and would be very interesting to read as an extended storyline - from either perspective (That of the host OR the parasite!)

To answer your questions:

  1. There are many possible directions to take the infection vector. Three I can think of off the top of my head would be: a] A virus b] A small but incredibly tough highly complex carrier parasite - along the lines of a Tardigrade c] Spores from a fungus All of these have the advantage that you can easily describe them as entering a "dormant" state which you could posit as being able to survive the extremes of space. The one that I would select if I had a lot of "room" in my story (eg multinovel series) would be something like the Tardigrade, as a part of the lifecycle of your parasite. This would allow for a massive DNA payload. To explain it properly would take a lot of words - whereas a Virus or fungal spore would take far less words - so if I was only writing a single story or book I would take the simpler route.

  2. I'll make a few suggestions for how I might handle certain aspects of the more complex Tardigrade vector. I would use the Tradigrade as purely the transmission vector. When it reaches a viable host (any creature that has a water based lifecycle) It can enter the host and break into individual cells. These are then transported throughout the host system - and once these cells reach particular kinds of cells in the host (which I probably would use axons) they would very gently insert themselves. The reason for using Axons is this allows the host to continue to function - until the colony is ready to completely overwhelm the host but also allow the colony to communicate. They would observe and release signals of their own until they began detecting signals from other tradigrade cells. Once they reach a certain critical mass of signaling - they begin to adjust the signals of the host slightly - over time obtaining greater control over the host - until they can begin completely changing the host actions to serve the needs of the greater colony. Once they achieve full control over the host - they would then move to the next stage - releasing colonising cells which are now targeted for each type of cell in use by the host. This will complete the colonisation process allowing the newly colonised host to become part of the superorganism. This is the point at which the process becomes irreversible. I would have the reproduction component of the cycle be on the expiration of the host - with the death of the host causing the host body to create millions of Tardigrade carriers - to then be sent forth.

  3. I don't know why the Colony or host would require metal to facilitate telepathy - I would have the colony achieve groupmind through a mechanism of quantum communication - effectively once being able to "switch on" the quantum communication plugging the colony into not just the other colonies on the local planet - but all the other colonies in the galaxy at the same moment. This will give the ability for massive superorganism status and God like intelligence - Entire planets of sentient creatures could be focused on a single hard question. This quantum communication should be part of the DNA payload of the transmission vector - but should require a massive increase in the number of cells - and possibly some kind of specialised organ - this would happen/ be created as part of the total colonisation of the host. This should have some preconditions for success and be capable of failing - this would give a bit more interest in plot development. Maybe failure creates a second class colonised host? Maybe failure causes the die out of the colonisation attempt and a host that "escapes" colonisation - creating an individual who tries to stop the colonisation of others?

  4. The Superorganisms colonisation protocol might depend on sending it's transmission vector to every possible location - regardless of suitability/ Sentience. Or more probably be directed by the superorganism to identify suitable target systems to send the infection vectors to. Once the quantum communication organ is activated - the superorganism will then direct all local hosts/ colonies in how to identify new vectors to send it's "Tardigrades" on slow journeys to ensure expansion new directions. It will direct creation of automated "probes/ drones" that are sent out to new stellar systems and is programmed to identify planets that are in the Goldilocks zone. Or perhaps the SUperorganism will identify suitable planets through Advanced tech - maybe by having the local civilisations create a massive space based telescope with a huge array of mirrors that enable it to actually look for planets better than anything we currently do. These probes/ drones can carry billions of Tardigrades in dormant mode for infection of the new system. Because thay can exist for centuries or even millennia in dormant mode - they don't need FTL to make it to another system. They simply need solar sails and time...

  5. Are there any problems with what you propose - no not really - at least IMHO. You just have to make the story interesting - you need to write relateable characters and you need to have the right amount of conflict. Possibly your conflict can hang on stopping the infection - possibly it can hang from the POV of the superorganism in overcoming a particularly troublesome new group of hosts that are naturally resistant...

  • $\begingroup$ @zxyrra your point number 2 is extremely valid. And is in fact the weakest part of my own answer (Commenting here because I don't yet have enough Rep to do it on yours) I really like how you have laid out your answer - it really gives a good approach for the transmission and identifies a lot of the challenges you would have to oversome $\endgroup$
    – kiltannen
    Jan 3, 2017 at 9:59
  • $\begingroup$ Thanks! I really like the tardigrade suggestion! As for #3, what do you mean by quantum communication? Do you mean like quantum entanglement facilitated-communication? It's my understanding that is impossible. $\endgroup$ Jan 3, 2017 at 16:59
  • $\begingroup$ @kiltannen Thanks, I like your answer nonetheless. $\endgroup$
    – Zxyrra
    Jan 3, 2017 at 21:22
  • $\begingroup$ The quantum thing feels a bit "buzzwordy". Time is irrelevant to an organism like this so lack of FTL travel or communication isn't a big deal for it and might even be an advantage... $\endgroup$
    – Tim B
    Jan 4, 2017 at 13:56
  • $\begingroup$ @Christopher Costello I was meaning some unexplained complex method of realtime communication amongst all the individual colonies in an entire galaxy. This would give you the brain capacity and thinking power to create a superorganism. $\endgroup$
    – kiltannen
    Jan 18, 2017 at 6:34
  1. Use an adapted virus as a carrier. Viruses literally live (if you consider them alive) to enter cells and change the way they work in order to reproduce - exactly what you want! Meanwhile, bacteria and fungi are significantly slower, and require more complex parts; they may be significantly easier to quarantine. Just shove all the complexity into the genes of a virus; if it doesn't fit, make it larger.

  2. No two aliens are the same, so neurological hijacking and rapid transformations cannot easily be accounted for. Life on different worlds may not use DNA, it may use use solvents other than water, or it may just live in something toxic to the invaders but not to itself.

    • While it's true that DNA is very likely to occur, and that water is common - so a lot of life should be easy to conquer - you cannot expect cellular organization or safe chemistry that you can work with in every species.
    • Even if the hosts have DNA, they're non-toxic, and they have cells just like ours, their brains may rely on different chemicals - or they may be organized differently - and their organ systems may be completely different - so a virus cannot simply go in with a single set of genes and expect to get the job done.
    • A possible solution could include examining potential planets ahead of time before colonizing, though this is difficult - and the results may not be promising.
  3. Say goodbye to metal-based telepathy. The parasite would need to

    • (1) Control the individual enough to find "food"
    • (2) Distinguish metal from other materials
    • (3) Find a metal the host isn't alergic to
    • (4) Determine quantity of metal necessary to generate microwaves for that particular individual
    • (5) Acquire that much metal
    • (6) Help the host digest it safely in a short span
    • (7) Learn how the host's body transports nutrients
    • (8) Move the purified metal to the brain
    • (9) Learn how their body builds microstructures, or learn how to assemble them safely in that particular organ
    • (10) Trigger the processes identified to build the structures
    • (11) Rinse and repeat for every individual creature involved in telepathy
    • (12) Use the machine
    • (13) Avoid damaging the brain tissue when its turned on

Even if all of the above steps were possible, you'd need to be able to fit that much computational power onto a single virus.

Consider having the virus itself acquire metal and transmit signals. It will be larger than a traditional virus, but much, much more reasonable.

  1. Compared to the biological aspects of this species, identifying host worlds is a piece of cake. If group minds are capable of applying higher reasoning and tactics to [their] cause of infecting as much as possible with maximum efficiency and they start out with spacefaring species, surely they can use those species' technology to locate other intelligent organisms.

  2. After you cover the logistics of infecting diverse aliens and facilitating change, I think you're all set.

  • $\begingroup$ Could I get a little feedback from the downvoter? I am willing to make a change, but by not leaving a comment you're essentially saying "I'm right, you're wrong, and you don't deserve to know why. Here, lose some rep" which isn't particularly polite. $\endgroup$
    – Zxyrra
    Jan 3, 2017 at 21:59
  • $\begingroup$ I'm not the downvoter but I think making the virus into an effective radio is highly improbable. Emergent behavior is a much more likely way to get intelligence. I also don't think viruses are viable here, as you say it's hard to see them being able to transmit between different alien life forms. $\endgroup$
    – Tim B
    Jan 4, 2017 at 14:04
  • $\begingroup$ @TimB Nothing is viable here; I just tried to give examples of how to make it closer to realistic. $\endgroup$
    – Zxyrra
    Jan 4, 2017 at 20:29

Ever seen an bacteriophage?

How about a Planetophage?

You need a virus: small constructs that have dna in it. You will have to use ribozymes for the following function:

  1. make nucleic acide from molecules in it's environment.
  2. replucates and transcribes dna or duplicates rna(the ribozyme itself)
  3. burn organic material for energy.
  4. makes coponents of an interstellar spaceship, then launch it away.

Rna origami involves the assembly of

1.any polygonal model of the stl or obj format. 2.any 3d shapes that consists of voxels, with minimal effort, by the base pairing of rna nucleotides. It is, therefore, possible to make spaceship parts with rna.

For the brain, use a DNA biocomputer: logic blocks binds to do logics and/or find the answers of a certain question. Make some small magnetite crystals, and place them on the output of your biocomputer, actuated by molecular motors and/or acruators(to wiggle or spin rapidly, radiating radio waves) as a form of radio, for sending instruction to your infected drones.

For the reason why this needs a biosphere to survive, it is mostly because that there is no effective form of energy generation, other than organic chemistry reactions by pre-existing organic molecules, with ribozymes alone, therefore, it needs a feedstock of organic chemical in a suitably favorable environment for combustion to replicate or do things, which means, a viable biosphere.

Your phage's life cycle will look like this:

First, adhesion and injection: the alien spaceship, or Capsid, crashes down on the planet of your choice, surviving atmospheric entry by a thick ,ablative hull.

Second, internal release: infective agents, with a integrated pore forming molecules, leaves the now broken hull, and they finds a cell, burrow into it, and releases it's contents.

Third, replication and transcription: once inside the host cell(s), the infective agent burns the readily available organic molecules, manufactures nucleobases (or using the host's own processes), and starts to replicate and transcribe it's detailed genome. multiple parts of the genome would be in separate packets(to reduce size and improve agility) and will cooperate.

Fourth, spawning: the active phage genome now transcribes different RNA parts for various purposes, including new infectious agents, vehicles for resource gathering and transport, etc. after all, biology is just advanced nanotechnology that can replicate itself. The rest is just Plague inc. gameplay. After a few months, the phage would have hijacked the planetary biosphere to produce it's own parts, and the spawning begins: from nanoscale to macroscale, billion of RNA parts self-assemble in an orderly and methodical fashion, building multiple new spaceships, each have it's own biocomputer, each packed with the phage DNA genome, each can infect another planet and repeat the cycle.

Finally, lysis: After the assembly of new Capsids and the packing of the copies of tha phage genome, The large biocomputer "Brain" of the infection now uses detector structures to look for other planets with a suitable biosphere, then send the ships en route. As this requires a massive amount of energy, all remaining host would be burned as fuel(to provide electrical energy for, as an example, a laser drive base station), completely sterilizing the planet, consuming all the biosphere.

Now, the new duplicate phage Virions fly off and land on other planets, starting the cycle again.


I don't see something like this evolving though it certainly could be designed.

Bacteria amoeba virus fungus. Those are categorized based off naturally occurring life. Some bacteria are photosynthetic, fungi tend to eat dead things and form a symbiosis with plants, amoeba are just weird, and viruses are too simple for complex programming. A synthetic organism doing this wouldn't really fit into an existing category. Just remember that evolved cells are naturally occurring microbots. The below is basically biological utility fog in the micrometer range instead of the nanometers range. Though microscopic cells still have nanoscopic organelles. Every cell is by default a molecular 3D printer. Viruses are not cells because they cannot self replicate. They are obligate intracellular parasites that hijack the replicating hardware of actual cells. I'm not sure how to make an interstellar virus due to a viruses very small size and limited programming capacity.

For interstellar travel have it form into giant space whales that uses sunlight up close and radioisotopes in the deep interstellar void plus reaction mass. Slow but effective. If they are intelligent enough they can create stellar lasers for thrust energy and communications.

Metals are not needed for radiotelepathy. Sure alkalines like magnesium and potassium could be used as ion pumps, but hydronium ions could also be used.

When landing on a planet it would go into or orbit, decel using the planets magnetic field or solar wind, powered by sunlight, then break into smaller chunks and decrease it's density to slow down aerodynamically.

It's attracted to the electrical stimulation of the nervous system and kills the organism soon after infection, but do to it's landing method it gets dispersed in the air and water so infecting more won't be an issue.

I suppose the act of neurodegeneracy could make the infected temporarily behave as zombies maximizing the local rate of infection before host death. Then consume all the biomass of the various hosts, basically all life on the planet, then grow a tethered ring to launch into orbit,reform into space whales, and move on.

Forming into mega telescopes will let it see very high resolution images from dozens of light-years away so that it can plot a course.

Such a creature wouldn't actually need to eat life, just the materials that carbon based life is made of. It should also envelope asteroids and digest then when enough sunlight is available.

We do not currently know if artificial gravity, or gravitational repulsion is possible. If it is then maybe it can be done organically. Maybe dark energy can be harvested.

If it can be done organically then getting in an out of a gravitational well would be much easier, and it would harvest dark energy all along the path towards the next host.

But solar power/ radio isotope powered shape shifting sapient spacewhales using reaction mass to very slowly travel interstellar space most certainly is physically possible. It would have to be designed and it would be a very slow trip.

Maybe organic low energy nuclear reactions are possible? Nobody knows yet.

Some answers are better then mine but that's what I've got.

  • $\begingroup$ Can you elaborate more on the "grow a tethered ring" statement? $\endgroup$
    – phil1008
    Jan 9 at 11:22
  • $\begingroup$ A tethered ring is like an orbital ring but in atmosphere. It uses tension and ring kept rigid with accelerators to prevent from falling. I say grow because life can form super strong silk, or limpet teeth, or ultra high molecular density polyethylene typically called dyneema. They grow the tethers, grow the ring, then grow a particle accelerator. The accelerator isn't meant to make relativistic particles. Just meant to use centrifugal force of tiny iron balls circling around to maintain rigidity. Overall a tethered ring is a big launching platform. $\endgroup$ Jan 10 at 15:50
  • $\begingroup$ @vladmirSilver Very cool! The idea of growing a megastructure of this scale is very original - but it seems believable. I could imagine such a plant initially evolving the ability to use active support as a way to get its leaves up above other plants to gain access to the sun, perhaps just by plumbing high-pressure water from a stream through a hollow vine. $\endgroup$
    – phil1008
    Jan 10 at 20:47
  • $\begingroup$ I don't see this evolving but it certainly can be designed. I'm glad you like it. $\endgroup$ Jan 11 at 21:47

Virus would probably the best bet since they can actually change the DNA of the host. Perhaps it could be a superior kind of virus that has multiple sets of DNA. One that it uses to infect its host to a zombie like state that is internally defenseless and the other for itself since it obviously wouldn't want that DNA. A bacteria or fungus couldn't "force" the body to its will. It would be cool if the virus's dna inside the host's nucleuses gave the host strong instincts(like an inner feeling or need) to protect the virus at all costs. So the host will still be in control but be trying to do protect the virus inside him at all costs even if it means killing his own kind as well as giving instincts to wanting to spread the virus. Multiple hosts could even have the urge to conspire to spread this virus. No telepathy would not be possible. Perhaps if you want you could have an infected scientist make brain computer chips that allow infected hosts to communicate through bluetooth or one of the satellites of the planet it is infecting. You could always have the virus make the host release certain pheromones however. These wouldn't allow the infected hosts to communicate ideas over long distance, but rather feelings short distance. Like when a host enters a building it would be able to tell that another one of the hosts are in trouble somewhere in the building. Anyway this idea would work pretty well I think. If each host is separately infected and still thinks independently instead of as a huge zombie like mass, they would have a better chance of spreading the virus. Being different will allow each person to help bring a new skill set to the table to helping spread the virus and saving the virus species.

  • $\begingroup$ The problem with a virus is that they have to be tailored to the specific organism they are infecting. An alien virus is going to struggle to interact with earth organisms in any useful way to itself. $\endgroup$
    – Tim B
    Jan 4, 2017 at 14:17

You could call the parasite Y. A simple stretch of DNA which does not do much until host maturity, at which point it hormonally hijacks the nervous system, compelling an amazing variety of persistent efforts by the host to mate with conspecifics and produce new individuals, half of which would carry the Y and the other half capable of gestating new individuals with the Y. At critical mass the Y carriers band together and devise a system leveraging language, writing, and religion called "culture" - this to control the necessary non-Y individuals (because the Y infected cannot gestate new individuals). Armed with culture, the Y infected form a superorganism called "society". The society of Y infected have the side benefit of wiping out or subjugating other life forms on the planet, and indeed altering the very surface of the planet maximizing the carrying capacity of the planet for Y.

  • $\begingroup$ Up-voted because it was a good analogy. $\endgroup$ Jan 3, 2017 at 17:03

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .