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No Biochemical Barriers / Alien Food Is Edible

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Examples of No Biochemical Barriers involving what people eat and drink.

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    Anime & Manga 
  • In Axis Powers Hetalia, Alfred's alien-buddy Tony is regularly seen snacking on the same fast-food junk Alfred does.
  • In Birdy the Mighty, Birdy can eat human food, and quite enjoys it, but needs to eat a lot more of it to survive.
  • In Death Note, Shinigami don't need to eat, but many enjoy human food anyway, as a form of Alien Catnip. Ryuk likes apples, and Sidoh likes chocolate.
  • Please Teacher!. Aliens love Pocky. Though the alien in question is half human.
  • Dita Liebely, the female protagonist of Vandread, samples the food from Hibiki Tokai's home planet, but she finds it revolting and inedible. Believing the opposite must be true for Hibiki, she feeds him food from her home world, which he found to be delicious. Following this, Dita has little problem spending time with Hibiki on the condition that she feed him. Although Dita considers Hibiki to be an alien lifeform, most outsiders would point out that they are the same species, just different genders.
  • In Cat Planet Cuties, getting access to Okinawan cuisine after Eris sends back a Food Porn-level description of it is one of the main reasons the Catians decide to come to Earth.

    Comic Books 
  • Green Lantern. The human Green Lanterns have problems getting good food at the Oan cafeteria. The chef just isn't that skilled.
  • Tenzil Kim and his fellow Bismollians from Legion of Super-Heroes can eat anything, except certain materials he specifically can't use his power against.

    Fan Works 
  • Oversaturated World: In Sailor Orbital Blue Oyster stops Kikai from eating Earth food based on this very issue. Kikai assures her that she recently used a magical spell to "align" herself with a native animal and so she's perfectly safe.
  • Discussed in Star Wars: Paranormalities. Gahmah Raan offers his guests Zolph, Grein and Hiriss (a human, a Chiss, and a Mirialan-human hybrid respectively, all species on the near-human spectrum) some tea brewed from a native leaf in his home. As Krishar is a mostly uncharted world and Krishari are a mostly unknown species (Gahmah being the only known one to have traveled offworld at that point), Zolph is understandably hesitant to drink the tea. As Grein has a Force ability that lets her filter toxins out of her body, she taste-tests it and confirms that it's safe, even if it doesn't taste great.

    Films ― Live-Action 

In General:

  • Many films where aliens, particularly sentient ones, eat humans (humans being eaten by alien beasts can be explained by the alien eating things that act like prey without knowing that it's bad for the alien's health).

By Movie:

  • Alien Nation: Newcomers can survive on Earth, but there are noted differences in their needs. They cannot drink (or even touch) salt water because it burns them like battery acid. Spoiled milk gets them drunk, so they drink it as a beverage rather than alcohol, which has no effect. The TV spin-off greatly expands on Newcomer differences.
  • The aliens in District 9 eat a lot of beef and pork, and have a craving for tinned cat food. There are some biological differences though: they don't just enjoy eating cat food, it tastes so good that it verges on being an addictive drug. It's described as being sort of like catnip is for cats to them, only a lot more intense. Initially this is played for laughs, until we later see aliens selling off advanced technology or even alien children for a few cans of it. They also like to chew tires, though it isn't clear if they can digest it, or if they just enjoy chewing it, like bubble gum.
  • The Men in Black films and cartoon imply that all alien immigrants and visitors to Earth can eat (or appear to eat, in the case of the Mobile-Suit Human-wearing Arquelliens) human food, although most of them need to in order to live as ordinary humans. Presumably those that can't eat Earth food find more-palatable corners of the galaxy to hang around in.


By Author:

  • Isaac Asimov's "Hostess": There are biospheres which aren't based on protein or even carbon, but the sapient species are all similar enough than an alien wanting to survive on human food only needs to bring some vitamin pills along.
  • John W. Campbell: Usually played straight in The Planeteers (the Penton and Blake stories), in which Penton and Blake are able to eat Callistan jelly fruit and stragath (although the latter squicks Blake out because it tends to move around while you're trying to eat it). Averted in "The Brain Pirates", though, when Penton and Blake become stranded on the outer-system satellite Pornan and fear starvation because all the food there is full of heavy metals.
  • C. J. Cherryh's works:
    • Tully, the sole human in the Chanur Novels, has no problem with Hani food.
    • In the Foreigner series humans must be very careful as to what atevi food they eat. Many "teas" and seasonings are deadly to them. The atevi can eat all human foods without problem, though human food is lacking in essential atevi vitamins, so an atevi can't survive on only human food.

By Work:

  • Animorphs uses that trope a lot, with varying plausibility:
    • Andalites are a species of mouthless centaurs which absorb nutrients from the grass with their hooves. Not only is grass apparently common on two different plants, Earth's seems to be perfectly healthy for them.
    • Similarly, Taxxons can apparently eat anything that bleeds. (Or will, even if they shouldn't.) Also, Hork-Bajir are capable of eating the bark of Earth's trees, although they admit it doesn't taste as good as the bark back home.
    • The technology that gave the series its name is based on absorbing DNA. It starts to make sense with The Elimist Chronicles, which explain that the Ellimist created the Pemalites to seed life on as much planets as possible, to beat Crayak at their "Will all life in the universe be utterly destroyed or not" game, so they probably used the same DNA-based cell for each one.
  • It is mentioned in a Dragonriders of Pern novel that humans cannot eat any of the native Pern plants and can only eat the plants originally brought from Earth, but they can eat the native animals.
    • Yet Klah (the coffee analogue) is made by steeping tree bark from a native Pern plant...
  • The Apicians in the Cordwainer Smith short story "From Gustible's Planet" are capable of eating Earth food (and think it's delicious). This is specifically said to be unusual, though.
  • Played with in the sci-fi novel Godspeed, a human colony world is cut off from the rest of civilization after something went wrong with every hyperdrive in the galaxy at once. Without imported food from Earth, the colony has to grow its own crops. While they're edible, and humans can live off them pretty comfortably, the local food has two severe health effects: one, puberty is delayed by nearly ten years, and two, something in the food causes a gross imbalance in the ratio of boys to girls born, such that girls are extremely rare. It's a plot point that unless they find a way to counteract this, the planet's population will collapse within a generation or two.
  • Present in Ursula K. Le Guin's Hainish novels. Characters from one planet frequently live on other planets, sometimes for years at a time (Genly, a Terran, on Gethen in The Left Hand of Darkness and Old Music, a Hainishman, on Werel in several short stories, among others). May be justified given that all of the people involved evolved from a common race, the Hainish, and so may have sufficiently similar biology to be able to eat one another's foods without complication.
  • In the Humanx Commonwealth universe of novels by Alan Dean Foster, the vast majority of species in the galaxy seem to be able to exist just fine on the same basic foodstuffs and in similar atmospheric conditions. One amusing application of the trope is that drug laws are all but impossible to enforce; just about every species has something another considers Alien Catnip as part of its essential diet.
  • In the Into the Looking Glass series, mostly co-written with Travis S. Taylor, the alien food is used as a diet plan, because while filling, it has no nutritional value, and thus doesn't provide energy in a form human biochemistry can use. Used in that anyone from one of the four biological patterns (called Green, Blue, Red and Orange based on the version of chlorophyll found) can eat anything of that pattern. However, even same-pattern foods may or may not be nutritious, or even safenote  - there's just a better chance of it being digestible.
  • In The Night's Dawn Trilogy, many exotic foodstuffs are imported from alien planets, and Earth plants are genetically tweaked to grow on other worlds; the best alcoholic beverage in the Human Confederation is made from the water accumulated in the flowers of Norfolk roses. A short tale describes how some of the first scientists to land there, while inspecting the local flora, tasted said water. Norfolk was cleared for colonization days later as a result.
  • Mentioned in Old Man's War, apparently killing and eating colonists of an alien species who happen to be inhabiting a planet you want is popular in the setting, and humans are just as willing to do it to other species as they are to do it to humans.
  • In Rama II, humans eat mana melons. These are alien eggs which look like fruits with green flesh and medicinal tasting green liquid. They are provided by resident bird-like aliens when the humans continually pester them for food. After analysing them with an Everything Sensor, Nicole determines they are safe to eat and they become the main sustenance of the crew. It is revealed later that these are the eggs of an alien species whose eggs feed the bird-like aliens. So one alien species' eggs is eaten by two other species harmlessly.
  • This trope goes all the way back to the first Space Opera, The Skylark of Space. Though the main characters are initially wary of eating Osnomian food, Seaton gives some Earth spices (as well as cigarettes) to an Osnomian without being at all worried for the alien's health.
  • The Space Trilogy: Humans can breath and eat just fine on Venus and Mars, even though those planets supporting species as alien to us as bipedal penguin-seals, sentient grasshopper-dwarves, and hundred-eyed, car-sized spiders. At the very least, its indicated that primal Jupiterian king, Maleldil the Young, formed the surfaces of the planets to suit life, so perhaps Maleldil just put in some extra hours to make each of the Solar System's atmospheres compatible with all forms of life.
  • Touched on in Star Wars Legends; though most species apparently have comparable digestive systems, a few unusual species, such as the Gand, enjoy foods that would either be indigestible or outright poisonous to others.
    • In an example from the Jedi Apprentice series, an Arcona, snacking on ammonia crystals, covers his plate when a human (Obi-Wan) reaches for the salt, explaining that sodium chloride is a dangerously addictive drug for his species.
    • According to Tales from the Mos Eisley Cantina, there is apparently only one human bartender on Tatooine, due to the insanely large amount of information about drinks that needs to be memorized so as to not kill customers with the wrong drinks. In another novel Han mentions that the bartender at the bar better not be watering down the drinks, since the species he's serving is allergic to water! Said bartender is also attempting to develop a perfect drink for Jabba. A single drop of the prepared liquor is enough to leave him convulsing on the floor.
    • After Tycho kills a cave creature in the X-Wing Series comics:
      Wes: What's that?
      Tycho: Might be dinner.
      Wes: Are you nuts? What if it's toxic?
      Tycho: Let's cook it and see how it smells.
      • Turns out that it's a ronk. Female ronks are physically nearly identical to males, but their flesh is highly toxic when eaten. Fortunately, Tycho killed a male.
    • Hutts are also apparently indigestible, even to the Sarlacc, but Hutts can seemingly eat anything; in one of the Tales from Jabba's Palace, it's revealed that someone is attempting to poison his food. The problem for the investigators? Over half of what Jabba eats is poisonous to most other species. It actually turns out to be a mistranslation; he thinks somebody put a curse on his food. Another example comes up in The Han Solo Trilogy; when Jabba wants a rival Hutt poisoned, it's tremendously difficult to find anything that will actually work.
  • A True Story, an Ancient Roman novel by Lucian, has the unbuilt form. Moon people, Sun people (yes, the sun is an inhabited world), and people from various stars all eat quite similar food to humans — milk, cheese, cabbages, onions, etc. Their worlds are also located inside Earth's atmosphere.
  • Somewhat touched upon by Harry Turtledove's Worldwar Alternate History series. The Race's biology and biochemistry are similar enough that they can live on Earth and eat some Earth biomatter with no problems. However, what would be slightly chilly to humans is beastly cold to them. Their home planet is basically a large desert with no freestanding oceans, and so hot that ice only exists in laboratories. Less prominently mentioned is that Earth is also a lot wetter than they are used to: Lizards stationed in Earth's tropics are very susceptible to molds and rots. Moreover, the common household spice ginger is so addictive to them it becomes their version of cocaine. It also triggers "heat" in their females.

    Live-Action TV 
  • Alien Nation expands on the differences between human and Newcomer biology. In addition to getting drunk on spoiled milk and burned by salt water, caffeine makes them dizzy, tobacco makes them stutter, and chocolate will give them a heart attack (like dogs). Meanwhile, certain things which are toxic to humans are harmless to them. Methane, alcohol, asbestos, and radon have no effect on them. They even use arsenic flakes as a food seasoning. They cannot absorb nutrition from food which has been cooked, so they eat meat and vegetables raw. As for hybridization, both humans and Newcomers initially think it is impossible, but later grow afraid that given how adaptable the Newcomer genome is, viable hybrids might eventually occur (though none have by the most recent entries in the franchise).
  • Babylon 5 features several examples of characters consuming food from alien societies. Sometimes there's no problem, other times... Well, this is what happens when Centauri try human fast food: "It tastes so good going down. Coming back up, it's not so good." Everybody can (and does) eat spoo. Even pak'ma'ra, who are carrion-eaters with a strict religious-based dietary code.
    • At one point G'Kar claims that every race has independently created their own version of Swedish Meatballs. According to the card game, even the Vorlons have one and it's apparently a sentient lifeform. Very much Played for Laughs.
    • When Londo Mollari asked what an item a salesman was offering, he said "Candy, only for carbon based life-forms who can metabolize sugar, otherwise it's decorative."
    • Alcohol appears to have exactly the same effects on Centauri that it does on humans — and, it's implied, on Narns and possibly other aliens as well. Well, Narns seem to have an alcohol tolerance maybe twice what is normal for humans (due to their overall robust physiology), so they just drink higher-proof booze. Centauri have a similar problem, as they imbibe so regularly sobriety is considered a vice they build up a huge tolerance. On the other hand, Minbari react quite badly to booze and become feverish and homicidally violent. Basically, alcohol is like PCP to Minbari.
    • In the novel To Dream in the City of Sorrows, Sinclair has to drink a certain Minbari beverage as part of the ritual to become Entil'Zha (Head of the Rangers), and is nearly killed by it. The Minbari knew this would happen, which is why that part of the ritual was delayed as long as possible, he only drank one sip, and they had a medical team standing by to treat him the moment the ritual ended.
  • Doctor Who:
    • The Doctor is apparently some kind of super-omnivore, with the exception of aspirin (and presumably other salicylates, like wintergreen Lifesavers) which is very toxic to Gallifreyans. However, the effects can be counteracted by consuming significant amounts of triglycerides (i.e. fat, in one specific case cocoa butter).
    • It gets even worse when the Slitheen (who are calcium-based life) are shown eating regular human food so as to keep up appearance and thus not blow their cover. Must have been a bugger avoiding vinegar all the time, maybe they should've started their campaign by invading France.
  • Food is played with in Farscape. The human Crichton is forced to subsist on food from a far side of the galaxy which has never even heard of humans, so therefore wouldn't be expected to have any idea what a human's body can process. Obviously, any time he has a chance to have food from Earth — even if it's all in his own head — he consumes it with relish. Additionally, food cubes are a standard processed food source used by many different species with no noticeable problems — though apparently, the whole idea behind food cubes was to make a standardized, cracker-like foodstuff which was molecularly simple enough that most carbon-based life forms can digest it.
  • Stargate Universe:
    • The crew of the Destiny often harvests foods from alien planets they stop by, simply because they're going to run out of Earth food in a hurry without any way to replenish it. They are, however, shown conducting tests on the food to ensure it is safe for human consumption (most of it tastes terrible regardless). Except for a few Funny Moments when Greer simply decides to take a bite out of alien fruit and is chastised by the medic for possibly poisoning himself.
      Medic: What are you doing, we don't know if that's poisonous?
      Greer: [deadpan] We will.
    • In another case, they try to establish friendly intentions with a new alien by offering it some (Earth) fruit. It hesitantly takes a bite... and begins spitting and coughing in disgust. Fortunately, it and its friends seem to understand that the humans were not deliberately trying to harm them.
  • A ground rule of Star Trek. Humans who like Earth dishes are in a distinct minority. In fact, almost any foodstuff mentioned is prefixed with an alien adjective ("Rigellian cheese", "Centauri trifle") while Klingon food gets its own vocabulary and a legion of human devotees. Practically the entire crew of Deep Space Nine seems to subsist on Raktajino (Klingon coffee). At least some examples may be cases in which Earth-derived foodstuffs are merely prepared using techniques introduced from other worlds. Most races do not like to eat Klingon food. Of course that isn't because it's inedible, but it's still moving.

    Tabletop Games 
  • Bleak World not only can the Alien Race eat human food, the occupation team is better at preparing red meat than most humans are.
  • In a Played for Laughs subversion, school dietitians in Teenagers from Outer Space react to the arrival of thousands of new and weird alien species in a unique way: they keep serving the same stuff they served all along. After all, it wasn't quite meant for human consumption anyway.

    Video Games 
  • Played straight in Borderlands. The occasional spit-roasted Skag seen at raider camps can be handwaved as the ill-educated locales (i.e. Rednecks) not knowing any better, but then you find that there is industry devoted to producing canned Skag meat which is quite popular. Also, T.K. Baha grew bladeflowers on his farm. They seem to be somewhat popular with the ladies there, suggesting the pollen of the plants is no worse than that of Earth plants.
  • Played straight with the Mothership Zeta DLC of Fallout 3. Throughout the exploration of the titular alien spaceship the Lone Wanderer finds numerous alien delicacies like squids and worms that when consumed restore your health with no obvious side effects. The alien equivalent to Stimpacks heal you just as well, but have the occasional side effect. Though the game in general does function on what people of the 1950s thought a world after nuclear war would be like, so it is most likely also showing what people from that era thought aliens would be like.
  • Halo often plays this pretty straight:
    • In Halo: Glasslands, the first human to visit Sanghelios (the Elite homeworld) is served Sangheili food with no problem, although the, um, texture isn't very appetizing ("Who ate that before you?").
    • According to The Forerunner Saga, the Forerunners can safely eat Earth-based food as well. Though it is mentioned that they cannot catch human-based diseases.
    • The reveal that a species known as the Precursors was largely responsible for seeding the Milky Way with intelligent life might go some way to explain all this.
  • In Sid Meier’s Alpha Centauri's Spiritual Successor Civilization: Beyond Earth, you can immediately farm the native flora and fauna, as well as grow terrestrial plants with ease.
  • Starbound: Taken to the point where plants of Glitch (who are a race of robots) are edible by all races, despite having clearly shown metal cover.
    • Additionally, the Florans enjoy eating practically anything... including other sapient races. The only exception are the Glitch. (There's no mention of how they feel about Novakids, who are made of stellar gasses. Probably not edible... but you can bet they've tried!)
  • Lampshaded in Star Ocean: Till the End of Time. If the town of Kirlsa is visited later in the game, Sophia can be found in a shop and states that she has scanned all the food and, to her surprise, it's all edible for Earthlings, although the flavors might be weird. This is one of many improbabilities in the setting that can be explained away by saying that the 4D Beings designed things that way.
  • Startopia: All aliens breathe the same air without complaint and synthetic food can be eaten by all species. However, some species will find certain biodeck environments highly unpleasant and specialist food can cause problems if eaten by some species.
  • Used in Sword of the Stars: Humans, tarka and hivers can all eat each others' foodstuffs with no ill effects (though non-hivers find hiver food terribly bland). Hiver biochemistry and taste organs are wired such that human spices and fermented goods (such as cheese) are near-narcotic to them (on the other hand, they have no reaction whatsoever to ethanol), and hiver warriors apparently eat garlic as a form of manhood test because the taste sensation makes it actually dangerous to them. Zuul are able to eat everything (or anyone) without any bad side effects, though being genetically modified this may be justified.
  • Played with in WarioWare: the alien character Orbulon is able to eat human food, but he has a Bizarre Taste in Food, including ice-cold french fries and spicy milkshakes. Additionally, he brings a giant blue radioactive alien carrot to a potluck, showing that at least some of his native food is inedible by Earth lifeforms.
  • Xenoblade Chronicles X: None of the various alien races seem to have a problem with human food, except the Zaruboggans, who consume toxic waste for sustenance (and humanity produces plenty of that to fulfill their dietary needs). Especially obvious with the Ma-non, who become absolutely obsessed with pizza, to the point that they will accept payment for their ludicrously advanced technology in the form of a few pizzas. This hilarity gets much darker when, late in the game, the wife of the owner of a pizza restaurant commit suicide because of the stress of fulfilling the Ma-non's endless requests for more pizza, causing her husband to go on a psychotic Ma-non killing spree. Meanwhile, in regards to humanity making Mira their new home, one of the jobs of BLADE's Curators division is to collect native material samples for research, including whether the native produce is safely consumable by humans.
  • Mostly played straight in Mass Effect, with humans able to eat most alien foods and most aliens able to eat human foods. The exceptions to this are the turians and quarians, species that have dextro-DNA instead of levo-DNA. This means that at best, a turian that eats human food (or a human that eats turian food) would get no nutritional value from it and at worst it triggers a lethal allergic reaction.

  • Freefall:
    • The incompatibility of amino acids on Pfouts with terran biochemistry was the reason for Dr. Bowman's experiments with uplifting nonsapient species, in lieu of very expensive space travel and terraforming. The Bowman's Wolf (including Florence) was to be a "proof of concept" test.
    • Played with in regards to Sam's biochemestry; since he comes from a planet with a relatively benign climate that forced few selection-pressures on his species and lacked anything like the asteroid strike believed to kill off dinosaurs on Earth, his protein structure is surprisingly simple, and delicious to most Terran animals. Counterwise, Sam can seem to eat most stuff humans can, and quite a lot else that may be poisonous to humans.
  • Saturday Morning Breakfast Cereal: Discussed in this comic. Where The Smart Guy actually points out that they wouldn't be nutritious nor tasty.
  • Generally present in Schlock Mercenary. Common food is freely edible by many different species. Averted on a specific occasion here, when a sea monster, being composed of highly toxic materials and nanobots, proves to be utterly unsuitable for consumption by anyone except Sergeant Schlock. Schlock himself is a carbosilicate artificial lifeform that is capable of digesting pretty much anything. His reaction to aggressive electroplating nanobots in the sea monster is that he admires food that fights back and likes the fizz.
  • Discussed in Spacetrawler when Dimitri visits an alien bakery, and handwaved with the approxiscan, a device which can identify compatible substances for one's biochemistry. In fact, Dimitri sells the aliens his grandmother's cookie recipe, which becomes insanely popular.
  • Subverted in Outsider. Alex Jardin tries to eat the food provided by the Loroi, but it doesn't agree with him and causes symptoms ranging from severe indigestion to vomiting. He's thrilled when he learns that ration packs were among the items the Loroi recovered from the wreckage of his ship.

    Western Animation 
  • In Futurama a Neptunian butcher sells both yellow and purple Neptunian slug, but explains to Bender that the purple causes "terrible nightmarish diarrhea". Presumably he means that's the effect on humans, since it would be odd for him to sell it if it did the same thing to Neptunians.
  • On Teen Titans, Starfire serves several dishes from her home planet. While most of the Titans aren't fond of her cooking, Terra truly enjoys it.

    Real Life 
  • Caffeine. To us, a mild stimulant. To a bug, a deadly poison of doom. Nicotine is somewhat similar — long-term use may not be particularly good for you, but it kills insects very quickly.
    • Even among mammals, you run into problems. Chocolate chip cookies with macadamia nuts and raisins are a rather easy thing for humans to eat, but to a dog the chocolate will cause potentially fatal arrhythmia and raisins are essentially kidney failure pills, while the macadamia nuts are a powerful paralytic. Some humans don't like onions and/or garlic, but most canines and felines will have their red blood cells dissolve if they eat enough.
    • Nor is it only a problem from one species to another. Cow milk is usually tasty to individuals of Western European stock, but Chinese or Thai groups have an impressive predisposition to lactose intolerance, since after infancy it is the default. It seems that only people from cultures where people traditionally drink milk from cows or other animals are lactose tolerant, since it apparently evolved when we started domesticating animals and taking their milk for ourselves, as being able to properly process the stuff even in adulthood would then have been beneficial. Since fermenting milk into cheese or yogurt destroys most of the lactose, people who are lactose intolerant can generally digest those foods much better than they can raw milk. This is why anybody bothered milking farm animals in the first place.
      • Some anthropologists believe that this is why the Native Americans turned against Leif Erikson's expedition to North America in c. 1000. The natives gave the explorers an offering of food, to which Erikson's group responded with an offering of their own — fresh milk from the goats they had brought with them. Unfortunately, the lactose-intolerant natives grew ill from the milk, and decided that Erikson had tried to poison them!
    • Similar patterns apply for alcohol. To ensure that water was safe for human consumption, early civilizations fell into one of two camps: those who boiled their water (primarily Asia, where dried leaves were added for flavour and was the origin of tea drinking) and those who fermented either juice or sweetened water, creating wines, beers, and mead. (It's not strictly the alcohol: the fermentation itself kills off pathogens, as the quickly dividing yeast absorbs all the food and starves them.) To this day people of European descent have a generally higher alcohol tolerance than Asians do, and among Europeans cultures that discouraged alcohol drinking will have less tolerance.
    • Also, brewing beer involves using boiling water to leach the sugars necessary for fermentation from the malt. In the same way for making mead, honey dissolves a LOT faster in boiling water, and if any pathogenic lifeform DOES contaminate the fermentation process, it is usually VERY easy to detect it in the product, adding another layer of protection. Honey itself is known to kill bacteria.
    • Pure nicotine applied to the skin will kill any mammal, humans included, in seconds. And caffeine becomes lethal past a certain level of blood content. It's not a matter of biochemical barriers; it's a matter of scale. A study by NASA of all people shows the results of caffeine, marijuana, Benzedrine (speed), and choloral hydrates (sleeping pills) on a spiders ability to make a web.
      • Hilariously spoofed here.
  • This works the other way as well. Death's cap mushrooms are, as the name suggests, potentially lethal (hello, liver transplant!) to humans, but are commonly eaten by other animals, especially deer. In fact, more than one person has died from eating death's cap after assuming it was safe because he saw some other animal eating it.
    • Oh, and they taste good, too. Death caps (Amanita phalloides), and the destroying angel (Amanita verna) have been used for assassinations because their good taste and harmless appearance conceal deadly amanitatoxins, which destroy the liver. First symptoms of acute liver failure appear 6-8 hours after poisoning, giving the assassin plenty of time to slip out unnoticed before the victim even realizes he's been poisoned.
  • Peppers are hot because they are filled with a chemical called capsaicin (or methyl vanillyl nonenamide, if you really must sound impressive). This chemical is toxic to most small mammals, but not to birds, which also cannot taste it and to some extent acts as an anesthetic. The seeds, likewise, can pass through bird digestive systems, but are rendered non-viable by mammals. The capsaicin, thus, serves by its burning sensation to prevent mammals from eating it, leaving the flesh for the birds which help spread the seeds. Humans are large enough that it doesn't normally kill or poison them, but most animals don't actively seek out food that burns their mouths...although on the other hand, the fact that humans do seek out food that burns their mouths can be seen as a victory for the pepper plants' strategy, since the human love of spicy food has resulted in the spread of the peppers far and wide around the world and all but guaranteed the survival of the species that humans have cultivated.
    • Dimethyl anthranilate, which is used as the principal artificial flavoring in grape soda, has the same biochemical effect on birds that capsaicin has on humans.
    • And the reason humans originally got to like spicy things was because they didn't spoil as readily, since capsaicinoids repel fungi.
  • Some avocados are toxic to some birds, and most other animals native to the regions in which they grow. It is hypothesized that the fruits evolved to be eaten by giant ground sloths which are now extinct, which would spread the seeds in their droppings. Nowadays guacamole-hungry humans and their knowledge of agriculture serve the same purpose.
  • Sales of royal jelly, a nutrient-rich secretion which bees feed to their larvae, mostly hinge upon buyers' belief that one of the effects of this substance on bee larvae designated as future queens - specifically, a greatly-extended lifespan - will transfer over to humans if ingested or applied topically. It's not toxic in this case, just useless due to extreme physiological differences between bees and people.
  • There's at least one genus of plant that stores up its energy as a carbohydrate that exists nowhere else in nature, rather than as starch. So far as is known, nothing can utilize this storage-molecule except the plant itself, so no herbivore bothers to try to eat it.
  • Played straight in the story of the Ghost Dance, wherein people dreamed of visiting the moon and eating animals from the moon.
  • There are very very few life forms on Earth that are able to digest plastics. This is why our garbage is expected to last for millions of years before it decomposes, and to leave behind toxic chemicals when it does. Recent observations of the North Pacific Gyre suggest that we're providing enough food to allow the few we do have to start to thrive.
  • For about 60 million years during the Carboniferous, it's believed that there weren't any decomposers on Earth capable of breaking down lignin: a key structural component of plants' supportive tissues. This meant that dead stems and twigs didn't rot on the surface, but became buried over time and gradually converted into coal beds. Only when fungi and bacteria developed the capacity to catabolize lignin did the carbon in tough plant parts start returning to the biosphere as it does today.


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