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The Vault - Fallout Wiki
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For general information about super mutants, see super mutant.
Mariposa super mutant
Harry, the epitome of super mutant stupidity
LocationNew California
Texas Commonwealth
Mojave Wasteland

Mariposa super mutants are super mutants created by exposure to the Forced Evolutionary Virus II from the vats of the Mariposa Military Base in California. They represent the finest form of super mutants, far more advanced than their primitive East Coast cousins created by imperfect strains of the virus.[1]


The following section is transcluded from Forced Evolutionary Virus. To modify, please edit the source page.

Body mass proportions in a Mariposa super mutant.

In humans, phenotypical changes brought upon by the Mariposa strain are substantial, accomplished by recursive growth patterns integrated in FEV. In order for the mutation to succeed, the subject needs to have a low level of radiation-induced damage[1] and should not have been exposed to the mutated FEV in the wasteland.[2][3] Subjects that do not meet these criteria will suffer a massive overhaul of the body's systems, leading to organ failure and an extremely painful death.[1][4]

The average super mutant is 3.2 meters tall and weighs in excess of 350 kilograms. Muscle accounts for over 75% of body mass, while bone and tissue are 10% each. Fat mass is exceedingly low, accounting for between 3-5% of body mass.[5] The increased muscle and body mass lead to a change in posture: FEV super mutants have a characteristic, hunched stance. The skin tone changes substantially and becomes gray with tints of light green, though as the mutant ages, it may become more green or even olive. The skin becomes much thicker and resistant to trauma, including cuts, bruises and damage from fire, acid or even gunfire.[5] Despite this resistance to trauma, completely destroyed tissues cannot be regrown, and will result in permanent scarring or organ loss.[6]

These changes are uniform across mutants, due to the aforementioned growth patterns and pre-programmed DNA loaded into the virus. This also has the effect of removing secondary sexual statistics, in favor of a pre-programmed masculine body shape. Primary sexual characteristics, such as the penis and testicles in males and the uterus and ovaries in females are unaffected.[7] However, super mutants are sterile, as FEV perceives gametes as damaged DNA and corrects them, resulting in sterility.[5][1]

Increased size of neural transmitters and synaptic receivers in the body give super mutants acute reflexes and heightened senses.[5] However, these changes are usually not accompanied by a similar rise in intellect. The FEV strain in Mariposa has a chance of modifying intelligence: while most people retain their pre-dipping intellect,[8] a majority of the remaining group experiences a loss (typically by 30%),[5] while the remaining minority of exceptional individuals may even experience an increase.[8] The loss is the result of damage caused by recursive growth and increase in brain mass, which may be accompanied by disfigurement and damage to existing neural patterns, causing loss of memory.[1]

The most stunning effect is practical immortality. Although theorized to only bring an approximate 10% increase in life expectancy,[5] the FEV strain in Mariposa results in a cell regeneration rate that exceeds cell death rate and prevents DNA degeneration through aging. The Hayflick limit is believed to have been completely overcome. This allows a super mutant to live for centuries, though if care is not given to exercising one's intellect, elder mutants may suffer from onset of dementia and Alzheimer's disease.[9] Death is made even more unlikely by the fact that super mutants are immune to common diseases[10] and radiation.[11]


The first step to create super mutants took place with West Tek batch 11-111, used to infect 15 chimpanzees. Growth and immunity levels were unprecedented: attempts to induce cancers through radiological and chemical agents were not successful. Increased aggression led to isolating the subjects by the science team, while violent epileptic seizures caused two subjects to expire. The rest was terminated after all data was mined successfully.[12]

Despite protests from the science team, on January 7, 2077, FEV research was transferred to the Mariposa Military Base,[12] to continue under the lead of Leon VonFelden and Robert Anderson. Batch 11-111 has been chosen as basis for further development and human experimentation, with a near 100% success rate on lab animals, granting an approximately 60% increase in size and potential 200% intelligence increase.[13]

A separate research effort was set up by Vault-Tec Industries in Washington, D.C. Vault 87 was established as an independent research center for Dr. Wayne Merrick, cooperating with the team at Mariposa. Despite his efforts, he was unable to improve batch 11-111 enough to reach satisfactory effects. Humans subject to his strains produced in the Vault 87 labs exhibited superior physical developments, such as increased size, strength and endurance to environmental factors, but were also characterized by significant mental retardation and extreme aggression to non-mutants.[14]

By comparison, the science team at Mariposa reached a full success, creating the FEV-II strain, able to create powerful super soldiers, exhibiting superior physical prowess, resistance to combat damage, aging and disease, as well as negligible loss of intelligence.[5] In certain cases, intelligence could even be increased by the virus. However, before the testing could begin in full, soldiers under the command of Roger Maxson rebelled and executed the science staff. With the Great War destroying the United States, Mariposa and research within was sealed by the soldiers and abandoned.[15]

The Master

The vats were rediscovered in 2102 by an expedition led by Harold, a major Hub merchant. Accompanied by Richard Grey, a brilliant exile from Vault City, he managed to crack the base security and infiltrate the lower levels. However, within the vats, the automated crane crashed into the two, knocking Harold out and flinging Grey into the vat with FEV. Harold woke up in the wastes outside the base, mutating due to exposure to FEV fumes, but becoming a special type of a ghoul-like mutant, rather than a super mutant. Grey, on the other hand, underwent extreme mutation due to prolonged exposure to the virus in the vat. His intellect grew exponentially, allowing him to comprehend even the most complex issues easily (or so he thought).[16] Grey methodically researched FEV, experimenting with animals and eventually, captured scavengers that strayed into the facility. It wasn't until a few failed mutations that he discovered radiation count to be a deciding factor in the success of the change, leading him to pick subjects more carefully.[16]

When his Lieutenant was created, he suggested a secondary reason for possible incompatibility. Reviewing available evidence, he concluded that failed mutations in relatively non-radiated humans are caused by the inoculating effect of a mutated FEV released during the destruction of the Great War had on humans it came into contact with. Such exposure was not enough to cause phenotypical changes, but enough to cause conflicts when the pure FEV in Mariposa attempted to change the DNA, resulting in the death of the subject. Grey (now calling himself the Master) concluded that prime subjects can be found among Vault populations. Super mutants were sent to uncover sealed Vaults and capture their inhabitants for processing. This move gave the Master unprecedented amounts of human subjects and in 2137 he began to mass produce mutants. The success rate was only 8-10%, but the Unity steadily grew.[17]

The number of test subjects was further increased by raids on Hub caravans and the establishment of the Children of the Cathedral in 2156. Captive caravan drivers and zealots underwent processing, both in Mariposa and Grey's seat of power beneath the Cathedral. In his lair, the Master and his staff experimented with FEV by injecting it into the brains of the subjects (usually the pineal gland, but also the amygdalae or medulla), triggering changes in brain chemistry. These experiments have limited success: four extremely powerful psykers were created, capable of theoretically wiping out the human race.[18][19] However, the usual effect included the creation of zombie-like mutants like Dane. FEV experimentation by the Master was abruptly halted in 2162, when he was killed by the Vault Dweller and the vats were destroyed.

After the Fall of the Master

Marcus, Sheriff of Broken Hills.

The destruction of the Unity and the Master caused the super mutant community to splinter and break apart. Bands of super mutants fled into the wastes in all directions, with charismatic mutants becoming leaders of warbands and even entire armies. The bulk of the super mutants led a disorganized flight northwards, into Oregon.[20] Gray paragraphs are based on Fallout Tactics and were not confirmed by primary sources, though high level events are stated to be canon in secondary sources. An army under Gammorin fled east, towards the Midwest, to carve out a place for themselves in the desolate wastelands. Eventually, they were united into a single fighting force by Paladin Latham, an Eastern Brotherhood commander thought lost. Defeated by the Brotherhood in 2196, they ended up integrating into the Brotherhood as its shock troops.[21] Gray paragraphs are based on Fallout: Brotherhood of Steel and were not confirmed by primary sources. Another group, led by Attis, attempted to rebuild Unity using the secret Vault as powerbase. Around 2208, they were wiped out.

Some super mutants remained in New California, attempting to integrate themselves. Though the Brotherhood of Steel worked to drive them away, some managed to stay behind and become productive members of society. The most successful attempt was led by Marcus, who founded the community of Broken Hills as a model for cooperation between humans and human-based mutants.[22] Likewise, the New California Republic eventually adopted laws enshrining tolerance and deeming hate crimes based on mutation a criminal offense (around 2202) and allowed for mutants to apply for citizenship.[23] Some even ended up serving in the Republic's elite special forces, the NCR Rangers.[24]

Mid and late 23rd century

The situation became more complicated with the emergence of the Enclave. Their excavation of the Mariposa Military Base in 2236 resulted in the creation of second generation super mutants from slaves used to unearth the ruins of the base. Though they were inferior to their first generation brethren, due to uncontrolled exposure to the virus, they were strong enough to destroy the Enclave troops left as a mop up operation. The Enclave sealed them inside the base by collapsing the entrance, but the damage was done. Eventually, the second generation mutants made their way outside the base.[25] Together with the die hard remnants of Unity plaguing the wastelands of northern California, they would remain an issue for years to come, affecting public perception of mutants. Less capable mutants, if captured, would face torture and mutilation at the hands of soldiers.[26] Some politicians even began campaigning on an anti-mutant platform to gain votes with the more bigoted strata of Republican society.[27][28]

Neil, a Mojave super mutant.

As such, many super mutants migrated eastward. Marcus led the group once again, after Broken Hills perished when the uranium ran out. He founded a settlement at Black Mountain in 2277, using the radiation at the site as a natural deterrent to humans.[29] However, a rift gradually developed between him and Tabitha, a nightkin officer from Unity. When Rhonda, her robot companion broke down, her mental condition deteriorated.[30][31] She gradually began to ignore his leadership.[32] In 2279, things came to an end. With no prospects for cooperation and clashes between nightkin and first generation mutants becoming more and more commonplace, Marcus left Black Mountain to establish Jacobstown.[33][34]

The two settlements became the primary concentrations of super mutant population in the Mojave by 2281. Jacobstown became a haven for first generation super mutants with a significant nightkin population led by Davison and Keene, enticed by the research and development efforts of Dr Henry, working on a cure for nightkin mental illnesses caused by their Stealth Boy use. Black Mountain became the center of State of Utobitha, a figment of Tabitha's deranged imagination and home to a very hostile group of nightkin and second generation super mutants.[35] The nightkin harassed travelers and merchants on the I-15 for supplies and food. Although the victims reported the matter to the NCR Rangers, they were unable to divert men and resources to take care of the problem.[36] Another problem emerged when Davison's group of nightkin left Jacobstown and attacked the Bright Brotherhood in their desperate quest to find Stealth Boys.


Fallout and Fallout 2

Fallout: New Vegas

Fallout Tactics

Fallout: Brotherhood of Steel

Van Buren

Fallout d20


  1. 1.0 1.1 1.2 1.3 1.4 The Vault Dweller: "{120}{}{How does the Virus work?}"
    ZAX 1.2: "{157}{}{My research into the Forced Evolution Virus, or FEV, indicates that it is a shifting-absorptive virus. It copies DNA patterns much like RNA, storing these patterns in exons.}"
    "{158}{}{These exons, combined with the FEV, are re-injected into the host cells in typical viral infectious fashion. This causes the host cells to 'regenerate' their DNA.}"
    The Vault Dweller: "{159}{}{How do you catch FEV?}"
    ZAX 1.2: "{162}{}{FEV is not 'caught', per se. It is not air-transmittable. Typically, infection is through injection, or direct physical contact with an FEV sample.}"
    The Vault Dweller: "{164}{}{Why isn't FEV affected by radiation?}"
    ZAX 1.2: "{166}{}{The FEV is a megavirus, with a protein sheath reinforced by ionized hydrogen. It is therefore capable of absorbing neutrons without becoming radioactive.}"
    The Vault Dweller: "{168}{}{If the FEV re-infects the host with its assimilated viral patterns, how does it make a 'better specimen'?}"
    ZAX 1.2: "{169}{}{The FEV is pre-programmed with introns of corrected DNA appropriate to the proper type of species. It therefore attempts to correct the DNA of the individual.}"
    "{170}{}{However, as the FEV is partially reliant upon the DNA of the individual, and also includes portions of its own recursive code, the effects can be unpredictable.}"
    "{171}{}{When inoculated into an individual with significant genetic damage, such as through radiation, it will cause the body's systems to suffer massive overhauling, leading to organ failure and death.}"
    "{172}{}{In a genetically viable individual, it re-writes portions of DNA, causing accelerated mutation, usually leading to recursive growth due to the FEV's own patterns.}"
    The Vault Dweller: "{174}{}{What potential long-term side effects exist?}"
    ZAX 1.2: "{178}{}{As the FEV causes constant regenerative update to DNA, it would effectively render the subject largely immortal, as cell death would be offset by augmented growth.}"
    "{179}{}{Additionally, as the gametes of the reproductive system consist of 'half-cells' using split DNA, they could be perceived as 'damage' by FEV, which would 'repair' them, rendering the subject sterile.}"
    "{180}{}{However, as my laboratory facilities are damaged beyond repair, this is conjectural. I cannot offer physical proof. You will have to, in human terms, 'take my word for it.'}"
    The Vault Dweller: "{181}{}{Could FEV mutation be corrected with a counter-virus?}"
    ZAX 1.2: "{184}{}{No. FEV does not retain unaltered original copies of the subject's DNA. Only a virus which re-infected the subject with original DNA could reverse the effects. Additionally, there is no known way to remove the FEV itself.}"
  2. The Vault Dweller:"{188}{}{Why am I a prime human ?}"
    The Vault Dweller: "{195}{}{So?}"
    Lieutenant: "{197}{LIEUT31}{So, you're from a Vault and have limited exposure to this mutated virus. The original FEV in the Vats should work quite well on you.}"
  3. Fallout Bible 0: "6. According to Chris A., the ghouls in V12 were exposed to radiation and FEV. I know Harold said the Vault door opened early or something, so the radiation bit makes sense. My question is, how were the ghouls of Vault 12 exposed to FEV? Harold was a special case, since he went to the Vats with... er... someone, whose shall remain nameless... and got dipped. How do you account for the others? - Richard Grey"
    "When the West Tek research facility was hit, it shattered the FEV storage tanks on levels four and five and released the FEV into the atmosphere. Through some means, perhaps propelled by the explosion, the virus was able to reach the ghouls quickly and the mutation process began even as the radiation was rotting away their bodies. How the virus was able to survive the blast without being sterilized is unknown... it would depend on what type of warhead cracked the West Tek facility like an egg.
    Actually, Harold never said he got dipped (although it's possible). He was exposed, however - being in close proximity to FEV is enough to cause mutations, as the Enclave slaves mining Mariposa discovered. I imagine the shield between the vats and the control room in Mariposa was meant to keep the virus contained."
    Note: The West Tek Research Facility is an underground bunker, which although was directly hit by a nuclear weapon did not release the Forced Evolutionary Virus. The FEV was moved to the Mariposa Military Base (a bunker under a mountain) before the Great War.
  4. Fallout Bible 8: "Peter Hopkins asks:
    I was reading version 5 of the Bible, and found a bit of a conflict with current knowledge... In one of your anwers, it was said that it was random whether the FEV increased intelligence or not. However, as far as I know, FEV increases the growth and integrity of ALL cells consistently, by doubling the amount of genetic material in the cells. In this case, an increase in brain size (assuming a healthy brain to begin with) and intelligence should be regular. Another theory could be that, as the mutant's brain grows, the mass of the mutant's body increases exponentionally and the brain would not be big enough to control the whole body and sustain the throught process of a human body. Also, it is possible that while intelligence does increase initially, the brain does not gain the resistance to radiation that the body does, and the mutant develops brain damage and shows reduced intelligence. Are any of the above true? PS There is a very good report documenting the effects of FEV and how it was developed on the No Mutants Allowed message board ( PPS I don't know about any so called 'purists', but i am hugely interested in the fallout world and would love to FOT background in the Bible.
    About FEV:
    That might be why some of the super mutants (such as the Lieutenant) are smart (or remain smart) - but generally, for some reason (I don't know off the top of my head, nor do I know if it's spelled out anywhere), they're about 30% dumber than a normal human being, if Vree's research disk in the Brotherhood of Steel is accurate. I wouldn't be surprised if the dipping process caused brain damage in dipped subjects - it's a hell of a shock to the system.
    Furthermore, everyone's favorite introspective machine intelligence, Zax, has the following to say about it:
    When inoculated into an individual with significant genetic damage, such as through radiation, it [FEV] will cause the body's systems to suffer massive overhauling, leading to organ failure and death. In a genetically viable individual, it re-writes portions of DNA, causing accelerated mutation, usually leading to recursive growth due to the FEV's own patterns. 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.
    Other possible factors that might be causing the super mutants' stupidness:
    - Most mutants have some degree of radiation poisoning, which may cause problems and brain damage, as mentioned above.
    - The process is unsafe - the mortality rate on "dippees" is pretty high. This is likely due to radiation poisoning.
    - Memory functions are "sometimes" impaired by the dipping, and intelligence loss may occur as well. Harold's memory wasn't in the best of shape after exposure.
    From the Pre-War experiment tapes, it looks like some mammals did display consistent increased intelligence (raccoons), while others didn't (the dogs) or even suffered brain damage (the chimps and the seizures). However, in an old Scott Campbell doc, there was a note that later subjects injected with the FEV (especially the chimps) hid their enhanced intelligence from their captors (or in the case of the raccoons, made a break for it).
    Furthermore, the FEV tests at West-Tek were done through injection, not dipping, so it's possible the dipping process itself that causes the brain damage. Possibly with the increased brain mass in the skull, the brain is "squeezed," and all that tasty juice runs out the ears.
    Still, on the other hand, a lot of the animals Grey talks about in his experiment tapes that were running around the Military Base were getting smarter from the FEV, and he himself became supra-intelligent.
    So there's a long-winded series of random answers. Moving on!"
  5. 5.0 5.1 5.2 5.3 5.4 5.5 5.6 Vree's autopsy report
  6. The cybernetic implants, branding scars, and the amputated tongue of Lieutenant, Dog and God, and Mean Sonofabitch respectfully are examples of permanent tissue damage.
  7. The Vault Dweller: "{132}{}{You can't possibly take on the entire world.}"
    Master: "{134}{Mast10}{I'm not after the world, yet. When I turn your fellow vault-dwellers into mutants, my forces will be too strong for any to stand against! But don't worry, you won't care. Care! Care!}"
  8. 8.0 8.1 Fallout Bible 5:
    "5. In F1 the Lieutenant said that the FEV raises intelligence. There are, however, very many dumb mutants. What can you say about it? And what do you think of my theory, which i've been using in my Fallout PnP campaign?
    Sorry, Pawel, for two things: I wasn't able to personally respond to your email because I kept getting bounced, and two, I wasn't able to comment on your FEV theory (as a reminder, I can't read fan-created material, so just send questions, comments, or facts if you can).
    As for the FEV enhancing intelligence, the original Pre-War FEV at West Tek did, and more consistently than the Fallout-era virus.
    The current Fallout-era FEV does enhance intelligence - in some people. Just not many. The Lieutenant was one of the lucky ones who didn't become a knuckle-dragging, butt-scratching moron after being dipped (and it may not have raised his intelligence, he may have been that smart before his dipping, but no records of his past exist to verify this).
    The FEV that was released out in the wasteland was mutated by radiation, so its effects changed. As for the FEV at Mariposa, the Lieutenant says the super mutants are smarter than humans ("We are highly intelligent and immune to disease"), which is only half-right, and he also says that the virus can also interfere with a person's memory, causing them to forget things. Obviously, the Lieutenant keeps forgetting that most of his super mutant forces can barely form complete sentences.
    Basically, the FEV in the vats only has a small chance of raising a being's intelligence (or even keeping it intact). The Master was one of the lucky ones. More often than not, it causes brain damage. It's also possible that the crude dipping procedure in Mariposa also caused imperfect mutations as well, reducing the chance of heightened intelligence.
    But to answer your question: the FEV at West Tek before the war caused increased intelligence in its subjects, but the FEV at Mariposa after the war rarely enhanced the intelligence of humans who were dipped. The reason for this is unknown.
    Chris Taylor says:
  9. Broken Hills mutants (Mutant miner, Old mutant), and those appearing elsewhere, are long lived, but some show signs of impaired cognitive function.
  10. The Vault Dweller: "{141}{}{How are you more advanced?}"
    Lieutenant: "{149}{LIEUT14}{Intuitively obvious to the most casual observer. We are highly intelligent and immune to disease. The strong survive! It is our goal to improve the human race.}"
  11. The Master: "{168}{Mast27}{Your humor will not save you now. Do you accept my offer, or not? Not! Accept!}"
    The Vault Dweller: "{169}{}{Not.}"
    The Master: "{171}{Mast28}{Radiation has no effect on us. The FEV virus makes us immune. Your argument is weak, and so are you.}"
  12. 12.0 12.1 FEV experiment disk
  13. FEV research
  14. Chief Physician's Terminal, Entry 87-34335
  15. History of the Brotherhood of Steel
  16. 16.0 16.1 Richard Grey's audio diary
  17. Fallout Bible 0
  18. Fallout Bible 3
  19. Mad scientist
  21. See this article for sources.
  22. See this article for sources.
  23. NCR history holodisk: "All law-abiding and peaceful people, human or mutant, are eligible to become citizens of NCR."
  24. Gond
  25. Fallout: New Vegas features second generation mutants, dum-dums.
  26. The Courier: "Do you know anything about that Super mutant walking around town?"
    Klamath Bob: "Oh, heh. Yeah, that's Mean Sonofabitch. I know the name sounds bad, but he likes it. He's one nasty old coot. Far as I can tell, he's one of them original Super Mutants, what came from the Boneyard. Wandered about after that "Master" fellow died. Eventually got caught somewhere around the Hub, back in NCR. Boy, they sure treated him mean down there. Cut him up so bad he can't talk no more. I tried to buy him, just so they'd stop hurting him, but they didn't want any of it."
    (Klamath Bob's dialogue)
  27. Mercenary note
  28. The Courier: "Who are you doing this for?
    Norton: "Won't name names, but some important folks in the NCR are sick of muties attacking their Brahmin herds. They want them gone from NCR territory. Maybe this group had something to do with attacking Brahmin, maybe not. Doesn't matter. We're getting paid to make them go away."
    (Norton's dialogue)
  29. Log 676: "Wow, I can't believe these old machines still work. This place looks pretty defensible, and the radiation should keep the majority of people away. looks like we've found a home, at least for now. First things first, though. We've got to get these corpses out of here. Poor bastards."

  30. Marcus made me type this: "The leader of this community, Marcus, said I should start keeping a journal to get me mind off of Rhonda. He also said I might find something interesting inside this stupid old building. What could possibly be interesting here? The only think that works in here is this junky old terminal."
  31. It's a radio station!: "It's amazing! This place is a radio station! If we can get it repaired, we can broadcast music across the wastes, just like Rhonda and I used to listen to. Ah Rhonda, how I wish you hadn't gone away. I asked all of the mutants here to help, but none of them could do anything for you. Which makes me doubt they can fix this place..."
  32. On the air!: "The radio station is fixed, and we've begun sending our message out into the desert. Marcus thinks I spend too much time in here, but what does a first gen know? Rhonda says they're just one step from dumb dumbs, and I agree."
  33. The elite!: "There was a fight in the yard today between some of us and the first gens. Marcus made a speech about how we need to work together, but why should we? We were the master's favorites! We don't need their help. Rhonda says we'd be better off without them."
  34. The Courier: "What makes this a "dangerous place?""
    Neil: "You must've heard her radio broadcasts? Though why a human would follow her invitation here is beyond me... unless you didn't listen very closely. The voice on the radio belongs to Tabitha, the "supreme commander" of Black Mountain - or, as she calls it, the "State of Utobitha." She took control of this place almost two years ago. The Super Mutants here do whatever she says - and she says humans are to be killed on sight."
    (Neil's dialogue)
  35. Alone at last!: "Marcus and the others left today. Finally, we have the whole place to ourselves! No more listening to lectures about what we can and can't say on the air. The airwaves will be free!"

    "Now Rhonda and I can host our own radio show like we've been planning. I don't know why Marcus always refused to let us do it before. He always started getting real nervous when I told him what Rhonda thought about things. Rhonda says he was afraid she was too smart to control."

    "Anyway, this is the start of a new era! The only downside is most of the dumb dumbs chose to stay."
  36. Fallout: New Vegas loading screen hints: "Travelers along the Long 15 have complained to NCR rangers that caravans have been harassed and attacked by fearsome Super Mutants living in the irradiated ruins of Black Mountain."