The Vault - Fallout Wiki

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The Vault - Fallout Wiki

Mutations result from altered organic cell DNA that can help, hinder or not affect an organism at all. Their causes include a large range of conditions, including radiation, viruses, mutagenic chemicals or simple DNA replication errors. These mutants are spread throughout the wasteland and characterize one of the many effects of the Great War.


Main article: Radiation

The various types of mutant creatures that inhabit the Wastelands were mostly created by radiation. This is from where mantises, geckos, radscorpions, brahmin and many other mutant species originated. Radiation is also how ghouls – decrepit, ragged, almost rotting, zombie-like victims of massive radiation poisoning – are created. Many ghouls were once Vault dwellers living in Vault 12 under the city of Bakersfield (better known as the Necropolis after the War). As part of the vault experiment, the blast door was designed not to close properly, thus those within the vault were exposed to massive amounts of radiation, and the majority of them that did not die became ghouls.

Ionizing radiation causes mutations by disrupting and breaking the molecular bonds of organic cells and, more importantly, the deoxyribonucleic acid (DNA) molecules that encode the genetic instructions used in the development and functioning of these cells. Providing it does not kill the cell outright, the radiation changes the cells' genetic code, whereby it is no longer able to perform the tasks it was originally meant to. The mutation then spreads throughout the organism via cell replication and reproduction.[1][2]

Forced Evolutionary Virus

A typical Mariposa super mutant

The other major source of mutations in the Fallout world is the Forced Evolutionary Virus or F.E.V. Super mutants, floaters, centaurs, Snallygasters, Grafton monsters, and possibly wanamingos were all produced on a large scale due to FEV infection.

FEV was developed by the Pan-Immunity Virion Project and was created to combat a disease called the New Plague. However, abnormal side effects were observed in test subjects. The test animals began to grow dramatically and their brain activity increased.[3] Seeing potential in the virus, the United States Army sent its own people to secure the project and began performing experiments on humans within the Mariposa Military Base. In addition to combating the New Plague, the project focused on turning men into abnormally strong and intelligent super soldiers.[4][5] At the West Tek Research Center in Appalachia, further testing moved on from simple super soldiers, up to the infection of the water supply to turn the nearby town of Huntersville into test subject material.

After the Great War, and the exodus of Captain Roger Maxson and his troops to the Lost Hills Bunker, the base sat quiet until it was discovered by a group of explorers including Harold and Doctor Richard Grey, most of whom died when they encountered the automated defense systems. Soon, only Grey and Harold remained. Harold was knocked out and woke up out in the desert looking like a ghoul. Grey was knocked into a vat full of FEV by a crane and managed to crawl out. He began to mutate in horrible ways, turning into a gooey mess of skin, bone and organs. He developed psychic powers, which were enhanced by consuming living minds to expand his own brainpower. Slowly, he started doing his own experiments with FEV.[6]

Grey found that many of the test subjects were metamorphosing into giant, mindless brutes with the brains of a child, if they survived at all. However, a rare few test subjects yielded super mutants. Immune to disease and radiation and blessed with exceptional strength, intelligence and endurance, super mutants were superior to humans in every way. They also possessed the exceptional lifespan of the mutated, but were total sterile. Grey – who now called himself the Master – lamented the needless destruction of the war. He decided that he would have to force humanity to evolve. Those who could not evolve would die.

Creating super mutants was a very hit or miss process. The great majority of super mutants produced by the Master and later his Lieutenant in Mariposa's vats were big, dumb brutes. Physically, there were vastly superior to humans, but they had the intelligence of children. What exactly causes some mutants to be brilliant and others to be stupid is unknown. As a rule of thumb, the less damaged or altered by radiation the subject's DNA, the better.

Aside from super mutants, the Master also created a variety of other creatures. No one is sure where the floaters came from, though some hypothesize that they are likely offshoots of West Tek experiments on flatworms,[7] but then again most would rather not know. Centaurs were created by tossing a varied mix of dogs, humans, and other animals into a vat and seeing what came out the other end.[8]

Military and scientific experimentation

Nightstalkers are prime examples of science experiments run amok.

Although methods like radiation and FEV, for the most part, seem unregulated, there have been many instances were mutation was the goal in mind.

Wanamingos were a pre-War experiment conducted by the U.S. military to make killing machines to aid in the conflict with China. However, after the bombs fell, wanamingos escaped into the Wasteland.[9] Deathclaws were of similar origin. Created by the United States military, this FEV dipped Jackson's chameleons were designed to replace humans in high risk, close combat and seek-and-destroy operations.[10]

Frank Horrigan, the Enclave's most powerful enforcer, was produced by a series of treatments involving a carefully modified version of the FEV, surgery, a variety of other drugs and the addition of a suit of power armor. Lastly, there is Harold, who looks a lot like a ghoul, but actually is a different kind of mutant than the standard necrotic meta-humans. Ghouls are the result of massive radiation exposure, while Harold was mutated by brief FEV exposure without being dipped into one of the nutrient vats containing the virus. Harold surviving was an oddity, resulting in a unique combination of a specific degree of exposure to the virus, a specific degree of prior radiation exposure within his own body and any number of other factors. While FEV does not produce ghoul-like mutants like Harold as reliably as it does super mutants when humans are infected by it, it does occasionally spit out something that looks like one. Another important exception is Talius, the ghoul-like creature that was hiding with the Followers of the Apocalypse and who was turned into his current state by FEV exposure, much like Harold, though under different circumstances.

In the Big MT research facilities, many mutations were deliberate, but without clear intention. Cazadores – large mutant wasps – for one were created by Dr. Borous. He was convinced they couldn't escape the research crater and were sterile, but this has been proven false by sightings of cazadors in large colonies in the areas surrounding the research facility. Also the handiwork of Dr. Borous, night stalkers were the result of the genetic hybridization of coyotes and rattlesnakes. Borous admits night stalkers were created after Dr. Calis dared him to splice mountain lion, eagle and condor genes together, but instead used the combination of coyotes and rattlesnakes.

Other mutants

There are a few other types of mutant creatures in the Wastelands that don't directly stem from FEV or radiation. These are mostly the intelligent animals and one spore plant encountered in Fallout 2. The intelligent spore plant and radscorpion in Broken Hills were another, separate experiment conducted by a scientist there. Occasionally, other intelligent animals have appeared here and there in the Fallout games, but all have been flukes. A race of intelligent raccoons living in an colony known as the Burrows was originally intended to appear in Fallout, but was cut due to style issues.

There are human societies that have undergone gradual mutations over several generations due to either environmental conditions like radiation exposure, or other reasons. Two examples are the Slags (mutated by genetic adaption to life underground) and the Beastlords (mutated by a unique form of radiation). Additional forms of these such mutants include the trogs of the Pitt, the swampfolk of Point Lookout, The Family of the Capital Wasteland, the Ghost people of the Sierra Madre, and the tunnelers of the Divide. Early after the Great War in Appalachia, a unique type of mutant surfaced: The Wendigo. The mutation appears to arise due to one of two factors: A human consuming human flesh and staying in low light subterranean environments for some time,[11] or large amounts of radiation surpassing typical Ghoulification, and rendering a human a Wendigo.[12]

Mutations in regard to canon

Over the years, different developers have been in charge of Fallout canon and have come up with different interpretations on this subject. Mutant creatures and where they come from is one of the most controversial topics in Fallout canon and it's very easy to annoy veteran scholars of the setting by getting things wrong or even just partially right.[13]

Chris Avellone seemed to prefer the "FEV explains everything" theory of mutation.[14] He suggests that when the Glow was hit by the Chinese warheads, the tanks holding the virus burst and the FEV was vaporized and shot into the air. It was then mutated by the radiation from the blast, and went on to help radiation create the various mutant animals we know and love as well as ghouls. The problem with this theory is that first off it's a bit redundant since Fallout radiation is already fully capable of producing the mutations seen in the gameworld. Second, we know from the Lieutenant's mention of inoculation from mutant FEV that any airborne strain of FEV could not cause these mutations.[15] If it did, why didn't any humans mutate from exposure to the airborne FEV? Furthermore, FEV causes sterility and if radscorpions, geckos, molerats, deathclaws and other creepie-crawlies are all products of FEV, they would be unable to breed and continue to be present in the wasteland. Avellone eventually admitted that he was wrong, and that most mutations in the Fallout world were caused by the ambient radiation.

Chris Taylor offers a different point of view on how ghouls are made. He suggests that when people with too much radiation damage are dipped, you get ghouls. When people with mild radiation damage are dipped, you get stupid super mutants. When people with very little radiation damage are dipped, you get intelligent super mutants. This would mean Harold is a normal ghoul. However, since the population of Vault 12 was never dipped, not all ghouls could be made this way, only that FEV would speed up the process slightly.

Enclave Mutation Policy

The Enclave holds the view that any "human" who has been "exposed" to the post-nuclear world's ambient environmental radiation is a mutant and that all mutants should be destroyed. The Enclave's definition of "exposure" would seem to mean that only Enclave members and those people still residing in Vaults count as "pure" human beings.


  1. Ionizing radiation on Wikipedia
  2. Damaging DNA on Wikipedia
  3. ZAX 1.2's information: "{173}{}{This recursive growth leads to an increase in muscle and brain mass, but is often accompanied by disfigurement and damage to existing neural patterns, causing loss of memory.}"
  4. FEV research: "2076. Unforseen side effects began surfacing in early 2076 with the PVP. Animal test subjects began showing an abnormal growth rate accompanied by increased brain activity. The U.S. government took notice of these discoveries, and in the interests of national security, moved a team on-site to secure and oversee the project, which was now dubbed the FEV (Forced Evolutionary Virus) project."
  5. FEV research: "2077... Effects upon human subjects remain unknown; although they are theoretically promising. The military, wishing to continue further testing, builds a large facility at the Mariposa military installation in central California. At this new facility, testing of the FEV virus continues on volunteer subjects from the military.
  6. Richard Grey audio diary
  7. FEV experiment disk
  8. Fallout Bible 0: "3. Are the radscorpions a product of the FEV virus? When you talk to the doctor, Razlo, in Shady Sands, he tells you that they were once American Emperor Scorpions but that he has no idea how they mutated because radiation alone couldn't have done it. For that matter, what about all of the other creatures of the wasteland? Which ones have been mutated by FEV and which ones haven't? Maybe in the bestiary each creature could have a stat that shows it's level of FEV infection."
    • The radscorpions are a result of a combination of radiation and the FEV virus, and Razlo in Shady Sands is correct - they were originally Emperor Scorpions that have grown... big.
    • FEV-Infected Critters in the wasteland include almost all the ones you've seen in F1 and F2:
      Most species of rats.
      Gecko lizards.
      Various varieties of plants, including the Venus Flytrap.
      Rumor has it some dogs were affected, but no one's seen any, so for now that's just rumor. Of course, the centaurs are a mash of human, dog, and various other parts... but hey, who knows how that mutation came about. Grey was probably messing around in one of his labs.
    • Creatures not mutated by FEV probably did not survive the aftermath of the Great War, with the possible exception of cockroaches... and perhaps normal ants, though there are FEV-infected versions of these species.
    • No one knows where those bird noises in Vault City came from.
    • I'll try to include a chart of FEV-infected creatures in future additions as well as other critters that you may not have seen in F1 and F2. Most likely a great majority of insects were affected (they tend to breed much faster, and their mutations tend to become evident pretty quickly as the generations advance), possibly beetles, some spiders, cockroaches, and other creatures."
  9. Fallout Bible 0, Answer me these questions three: 2. Does FEV really cause sterility? In Fallout 1 it seemed like the answer was a resounding yes, and a number of reasons for this were given by Zax and Vree. But then in Fallout 2 after you take Marcus to the Cat's Paw he says "I hope she doesn't get pregnant" and says that the FEV doesn't make mutants go sterile, it just makes it take a few years "to get the juices flowing again". Moreoever, the deathclaws in Vault 13 were infected with FEV and yet they are able to reproduce. So, does the FEV cause sterility or not?
    "...The wannamingos are a result of FEV virus experiments, but they are now becoming sterile. They are not aliens, but word is they were designed as FEV-tailored weapons for waging war on other countries... and they got loose. They do live a long time, but they were dying out at the time of Fallout 2. They have only been sighted in the F2 area and nowhere else in the wastelands..."
  10. Joseph (Fallout 2)'s dialogue: "{131}{}{What can you tell me about the deathclaws?}" (The Chosen One)
    "{146}{}{Well, let's see... Deathclaws appear to be mutated Jackson's Chameleons, the horned variety. There are a lot of similarities still present, but an even greater number of differences. The mutation factor is quite high. This species is highly intelligent, about the equivalent of an eight-year-old, with some individuals reaching human normal level. Their learning capacity is very high and they are capable of abstract thought and reasoning.}"
  11. Raiders (Fallout 76)#Gourmands
  12. Curse of the Wendigo - Part 1 & Curse of the Wendigo - Part 2
  13. An excerpt from Fallout Bible 5 in which developers Chris Avellone, Tim Cain and Chris Taylor don't agree from where certain mutants come:

    "27. I disagree with making Harold not a ghoul. During Fallout 1 the name "ghoul" was not yet as widely used as in F2. Harold could have disagreed with calling his mutant kind with such a name (which is not very nice). When you ask him about the ghouls he says:
    {1102}{hrold302}{Mutants. Doesn't matter what they call themselves.}
    I think it doesn't necessarily mean that he's not a ghoul. It just means that he doesn't want to be called a 'ghoul'. He says, that the ghouls are mutants, just like him, and it doesn't matter how they call themselves.
    I think the name 'ghouls' was either created for them by the Necropolis ghouls themselves, or by people who considered them monsters. As he looks like a ghoul, i think he would be considered one by both. Ghouls are not like supermutants, they are not all the same. It's only a name for people twisted by radiation or FEV (or both). There may be ghouls created only by radiation, and ghouls created only by FEV.
    I also think, though Harold was mutated in the Vats, that if you say that all the ghouls were created by the FEV, then there isn't much difference between Harold and other ghouls.
    Chris Taylor wrote:
    >>Actually, a dip in FEV has a chance of modifying Intelligence, but it doesn't always increase it. Some people do gain increased intelligence, a larger majority lose intelligence and most people remain the same. It also depends if people have enough radiation damage to be turned into ghouls or super mutants.<<
    If so, then people dipped in the Vats can become ghouls instead of supermutants, if they are radiated. I think that easily matches Harold's case...
    Fallout 2:
    {100}{}{You see a particularly leathery-looking Ghoul.}
    {101}{}{You see Harold.}
    {102}{}{You see a very old but still spry-looking ghoul.}
    {172}{}{Put a sock in it ya smelly old ghoul. Goodbye.}
    Loxley (F1):
    {244}{LOX_69}{Harold? He's a good enough sort, for being a ghoul an all. Lives on the south side.}As you can see, Harold is called a ghoul in the game.'
    Butch (F1):
    {233}{BUTCH46}{Alright, so it wasn't the Death Claw. But what would the mutants in Old Town want with our caravans? Unless it's some kind of conspiracy.}
    As you can see, there are more muties in the Hub Old town, not only Harold (though we don't see them in the game). And they are all called both 'mutants' and 'ghouls'.
    I think the point is that you call 'ghouls' only the ones that were exposed to 'wild' FEV in the air and radiation, and not the ones that were screwed-up results of dipping (like Harold and Talius). I think both kinds should be called 'ghouls', because, though they were created with different methods, the result is identical, and they were both result of radiation and FEV (ghouls of Necropolis are radiated people that were exposed to mutated FEV in the air, and Harold and Talius are result of dipping people with radiation damage - think this is what Chris Taylor meant)."

    "All good points - Tim Cain and Chris Taylor agree with you, and they say Harold's a ghoul. To quote statements within the past week:"

    "Chris Taylor: Ghouls are a type of mutant.

    Harold is a ghoul. He's also a little special. Super Mutants are humans with no or minimal radiation damage who have been exposed to FEV. Ghouls are humans with significant radiation damage exposed to FEV.

    Harold is, well, Harold."

    "Tim Cain: I know we treated him as a ghoul, but not a Necropolis one. He may have been irradiated before or after. All I remember was that he went in there with the guy whose name I forget (the one who fell into the vat and became the Master), and only Harold came out. Harold's memory is totally whacked, btw. ...most people don't know when they get irradiated, so he [Harold] just may not know what happened to him. I do know that radiation and FEV do not mix. Mutants are immune to radiation effects, but an irradiate human is killed by exposure to FEV. So one thing is sure: Harold is not a mix of radiation and FEV. He's got to be one or the other, and I think he's a ghoul."

    "According to Chris, ghouls are irradiated humans exposed to FEV."
    "According to Tim, ghouls are due solely to radiation."
    "Both agree Harold is special. And I don't mean handicapped.
    "Officially: Ghouls are a mix of FEV and radiation. Harold is a mutant who resembles a ghoul. Harold may have had some radiation damage before he was exposed to FEV, but his mutation (outside of his surface appearance) makes him different than a ghoul. Most ghouls are the result of extreme radiation + FEV exposure, but Harold's change was due primarily to FEV exposure (again, he could have sucked up a few rads in the wastes without him knowing, especially considering how long he ran caravans in the wastes)."
    "He is hideously mutated enough so that he looks like a ghoul, but he's not technically one, and this is the mistake that Loxley makes (Loxley only judges a book by its cover, and he knows nothing about genetics or anything beyond a surface appearance)."
    "You can call him a ghoul if you want, but the official answer is:"
    ""Harold is Harold." Harold's special."
    "BTW, glowing ghouls are ghouls that suck up too many rads after they have become ghouls. We originally wanted Lenny in F2 to be able to turn into a glowing ghoul when he drinks too much radioactive liquor, but we didn't put it in."

  14. Fallout Bible 9#FEV and vegetation: Specifically, carrots
  15. LT.MSG: {194}{LIEUT30}{The FEV was mutated by the war radiation. Those living in this desolate wasteland have been exposed to this mutant FEV, essentially inoculating them from the full effects.}