In my world, an intelligent species has evolved to the point of space travelling. However, this species can eat only one single type of food (which is a product of another species on its planet).

It cannot use any other species as food, and it cannot artificially create food which is equivalent, despite having technological abilities.

Is this situation possible? What kind of evolutionary/biological/technological conditions would possibly result in such scenario?

  • $\begingroup$ It would depend solely on their ability to bring bring that food source along with them in travel. If it is a produce of another species, then they would have to bring that species along with them as well as whatever is necessary to sustain that species. $\endgroup$
    – Arvex
    Commented Jan 28, 2017 at 14:04
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    $\begingroup$ How many specimens of that food-species exists on this planet compared to the amount of the space-travelling-species? And how much of the food-species is needed to sustain the space-travelling-species? I would imagine that it will be very hard to create such a situation. If your food-species has problems, because something started to hunt it, your space-travelling-species will go extinct pretty quickly. The food-species needs to pretty insanely abundant, resistant to climate, easy to kill, fertile, with no other predators and rich in nutrition. $\endgroup$
    – Secespitus
    Commented Jan 28, 2017 at 14:12
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    $\begingroup$ Koalas only eat eucalyptus leaves. Pandas only eat bamboo. Maybe your spacefaring race is like them. They would be great for a movie: super cuddly cute CGI aliens each hating the other because of the other race's weird diet. In the end, each one tried the other type of leaves and they like them! All are friends. Except the pandas get diarrhea. $\endgroup$
    – Willk
    Commented Jan 28, 2017 at 14:57
  • $\begingroup$ Thanks for the answers and ideas! What about the second part of my question - is it possible that a species is intelligent enough to go space travelling, yet has no technological option of mimicking the chemical ingredients of its food (as we do with artificial mother's milk), meaning it would actually be forced to carry it along and grow it? $\endgroup$
    – Ayal
    Commented Jan 28, 2017 at 17:56
  • $\begingroup$ "something produced by only one other species".. Then I hope it is honey and not poo! :) $\endgroup$ Commented Jan 29, 2017 at 3:05

7 Answers 7


Consider something like the leaf cutter ant, which eat nothing but fungus, they evolved agriculture long before humans existed. They harvest plant material to farm the fungus and have been doing it for so long they can barely digest anything else. They even produce a biological antibiotic to kill off anything that might compete with the fungus.

It would be easy to see a strong evolved disgust response against even trying to eat other food in such a species. They farm something to feed the fungus which can be fed a variety of things, then only eat the fungus, that would allow them to evolve behavioral plasticity since they have to find things in new environments to feed the fungus. Plus fungus agriculture has evolved at least three separate times in insects so you completely justify it on an alien species.

Any advanced civilization could develop the technology to synthesize their food, but there are many reasons they would not bother, especially on a large scale.

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    $\begingroup$ But why would a highly advanced society be unable to synthesize its food? In the end it’s just a bunch of molecules. $\endgroup$
    – Michael
    Commented Jan 29, 2017 at 10:30
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    $\begingroup$ We can't synthesise meat, sure we can grow it in a lab using cells but how is that different than farming a fungus? It's the same reason we don't synthesise starch, becasue it is way WAY easier and more energy efficient to grow it. Starch could be produced from oil, but it would incredibly costly, yields very little, and is done basically by copying how plants do it anyway. Then you have the issue of having to synthesise all the other macronutrients and a slew of micronutrients. There is just no reason to put time in the effort into designing the infrastructure needed to do it on large scale. $\endgroup$
    – John
    Commented Jan 29, 2017 at 14:07
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    $\begingroup$ But the meat doesn’t have to look like meat. We only need the protein, fat, iron and all the other good stuff. You can buy all macro and micronutrients you need and survive on them (Soylent is constructed from such ingredients). I don’t know how much of those nutrients are extracted from plants and how much is actually synthesized in a way. They are probably not starting with pure elements. Starting with pure hydrogen would be the ultimate solution. $\endgroup$
    – Michael
    Commented Jan 29, 2017 at 14:57
  • $\begingroup$ Most (excepting minerals) are extracted from biological sources, it is just easier. $\endgroup$
    – John
    Commented Jan 29, 2017 at 22:42

One of Ian Bank's crazier ideas is a sentient species that grew up as a parasite (think tick/flea) of another. This kind of scenario fits your need very well.

For food sources, it's usually next to impossible that you wouldn't find another source of food that more or less does what your main food source does. But parasitic creatures are different. I'm not sure what exactly causes this, but the evolution of fleas closely follows that of their host and fleas were used to work out when humans and primates went their separate ways through evolution, since the flea species also diverged.

I'd guess that with parasite creatures, it's not just the food they get, but also how they get the food. The method of feeding might be peculiar, with only a certain special way to get under the skin and into the blood of the animal they feed on. Or maybe there are only certain special chemicals that cause hunger or various bits of the feeder's anatomy to be stimulated to "eat". In the way of milk, they may know all the chemical constituents, but they might not be able to synthesize it.

Anyway, that avenue is worth a bit of research.

  • $\begingroup$ was about to say parasite. +1 $\endgroup$
    – Zxyrra
    Commented Jan 28, 2017 at 17:12
  • $\begingroup$ Do you have a reference for Ian Bank's parasites? $\endgroup$
    – coredump
    Commented Jan 28, 2017 at 20:37
  • $\begingroup$ @coredump I think this is Iain Banks, and the novel is Matter. $\endgroup$ Commented Jan 28, 2017 at 21:12
  • $\begingroup$ @bright-star Sorry for the typo, and thanks a lot for the reference. $\endgroup$
    – coredump
    Commented Jan 28, 2017 at 21:16
  • $\begingroup$ @coredump No problem. I could be wrong, anyway. The only one who knows for sure is the answerer. $\endgroup$ Commented Jan 29, 2017 at 1:34

The evolution of stomaches is much slower than the evolution of technology. There is evidence of the use of fire going back 400,000 years or more, but humans kept their large seed-grinding teeth and smaller skulls up until about 250,000 years ago… That's a big gap, but presumably we could not have evolved our bigger brains until after fire gave us food that was already partially broken down. We are still not very good at digesting uncooked protein, even though it's now considered essential to our diet.

Our brains are also hungry organs that consume almost 1/4 of all our calories.

So it's not much of a stretch to have an intelligent species that became dependent on a certain type of food (or how that food is processed). However, your problem is: with all this technology why haven't they invented "space food"?

In Jared Diamond's book Collapse, he talks about many cultures that died out simply because they stubbornly refused to adapt. He specifically talks about Viking colonists in Greenland who refused to change their diet to fish. They knew the indigenous people ate fish, but the Norse instead tried to keep their "grain and sheep" diet which was unsustainable. They insisted on keeping their own cultural identity and starved.

With all the allergies and biodiversity on our planet, the main reason certain foods are taboo is because of culture and religion… Maybe there were practical reasons to reject certain foods as "unclean" and that got woven into religious law, but those reasons are no longer true and seem arbitrary today. However people dedicated to their faith continue to reject them. There is also the weird case that the tomato was thought to be poison for 200 years.

I suggest you combine some aspect of their evolution that makes them dependent, but emphasize their cultural taboos or religious laws that prevent them from making necessary adaptations.


It's highly unlikely that an intelligent species strictly depends on one single "food species". Two main reasons:

  1. Evolution: The more narrow a species ecological niche, the less resilient the population is. So almost every species can deal with at least a small spectrum of nutritional sources. If it could not, it would not have survived.

  2. Chemistry: Even if your species relied on a single food species, technically the food species is the result of bio-chemical processes. If these processes in an organism lead to an appropriate food source for your species, the same processes would lead to appropriate food sources if artificially initiated, e.g. in a lab or an industrial environment. Likely it is only the mix of a few parameters, maybe chemical compounds, that make the food species appropriate. I cannot think of any reason, why it would be impossible, to get these right in a controlled environment such as a lab.

The idea of intelligent parasites is interesting... however, the most intelligent parasites I can think of, are insects. And insects, as we all know, tend to be rather small animals, which also limits the size of their "brains" or ganglia. Furthermore, the dependence on an appropriate host brings severe limitations to the extend of development. This is because the environment a parasite has to adopt to, is its host. And this environment is really limited, in every way.

In my opinion, your idea is rather unconvincing.

  • $\begingroup$ Well there are plenty of species on earth which are dependent on one food source (giant panda, koala, snail kite, etc.) It may not literally be the only thing they eat (IIRC pandas have been known to occasionally eat carrion), but they are definitely 100% dependent on it to survive. The synthesis thing would be a larger problem, though. $\endgroup$ Commented Jan 29, 2017 at 4:19
  • $\begingroup$ The parasites can be bigger if the host is bigger. This is especially the case if the species is aquatic or the gravity on the planet is low; a whale-sized host can have some pretty big parasites. $\endgroup$ Commented Jan 29, 2017 at 6:19
  • $\begingroup$ Well, there are a few species that feed on one single food source. Although you will find examples, they are really a minority. Your example of Panda and Koala also show that those species are very vulnerable and can easily go extinct. Also you have to note, that often a limitation to only one food source is primarily a behavioural limitation, not really a metabolic limitation. In the case of an intelligent alien species, this limitation could easily be overcome, even if there was a metabolic issue, too. $\endgroup$
    – Thodor
    Commented Jan 29, 2017 at 9:16

Well, your species obviously has an extensive food production industry on the home planet, the question of whether a spacefaring species could exist with a dependency on such a specific food source boils down to one question, how hard would it be to take the production cycle with them into space?

Maybe, instead of trying to figure out how to artificially produce the food, maybe their technology focused on making the industry mobile.

i.e. Farms in space


The tricky part of this question is why they can't synthesize suitable food, as single-food dependent animals are pretty well known on Earth - giant panda, snail kite, etc. (Many of these animals do eat something else occasionally, but they are definitely totally dependent on one food species for survival. Similarly, the larval-food dependence of many moths/butterflies.)

Some possibilities:

-non-native technological development: the space travel technology doesn't come from a generally high tech base but was obtained from aliens or uncovered from the ruins of a previous destroyed civilization on their world.

-impaired biological development: something about them or their world makes it extremely hard to develop biology relative to the other sciences. It could be some misleading fact (introduction of alien species in the distant past or really high rate of radical mutations) leading to wrong theories of biology becoming dominant, or something cultural (a biological-weapons war almost made them extinct so genetic research is forbidden, long period of dominance of a world dictatorship pushing something like Lysenkoism).

-aberrant means: their space travel tech uses something like FTL or teleportation that doesn't fit well with our physics, and turns out not to require a high general level of technology.["The Road not Taken" by Harry Turtledove] Possibly their brains are wired fundamentally differently from humans', so something is obvious & simple to them that isn't to us.


Check out Peter F. Hamilton's Pandora's Star and Judas Unchained of the Commonwealth Saga

The main threat is a advanced alien species that fits your requirements, although it may be able to produce the food after alien-forming other planetary bodies.

  • $\begingroup$ Recommend taking relevant quotes from the link and including them in your post. $\endgroup$
    – Anketam
    Commented Jan 29, 2017 at 13:21

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