The Practicality of Vault 68: Trickle Down Genetics

The Vaults were never designed to rescue the people that lived inside them. They were a vast social experiment, designed to study pre-selected segments of the population.” So begins the Penny Arcade comic One Man and a Crate of Puppets.

Fallout Vault 68

For this series, we’ll be deconstructing a handful of Fallout vaults (both canon and fan created) to determine which, if any, could be viable. We’ll start with Vault 68, an experimental environment comprised of 999 men and 1 woman.

At first glance, this vault seems doomed to fail. A new child can only be born every 11 months. The larger difficulty is to create as many children as possible before the vault’s only female passes reproductive age. Assuming the vault door doesn’t open for 100 years, this experiment is barely, if at all, possible. To explain the rationale behind this piece, we first have to understand the vault’s social structure.

  1. Socially

My rationale for the future of Vault 68 relies heavily on establishing a social structure within the vault. I believe the only way for the first woman (who we’ll call Eve) to survive would be to take advantage of her position within a month of entering the vault. Eve’s best bet would be to ally herself with the most powerful man in the vault, the Overseer.

Once Eve and the Overseer had established a partnership, Eve could begin having children. I suspect for the first few years, Eve would be in constant danger of violence from frustrated men in the vault. To ensure Eve’s safety, the Overseer would establish arranged marriages between his daughter(s) and Vault 68’s security team, who in turn would arrange marriages for their daughters. Vault 68 would devolve into a caste system, where women would become currency. I call this “trickle down genetics.”

Once a handful of security guards were given sexually mature wives (likely 17-18 years after entering the vault), they would pass their daughters to the next most important caste. Thinking of this in a Fallout Shelter mindset, I imagine doctors and workers either in the power plant or waterworks would threaten to cut their services and utilities until marriages were arranged.

I suspect the lowest caste in Vault 68 would be either cooks, handymen, or janitors; essentially anyone who did not contribute to the security or immediate needs of the vault. The way I see it, the experiment could end in two ways. The first is that daughters of the lowest caste are married off to the Overseer caste, where partners would be 1/20th related. The second is that the vault door could open after 80-100 years; its inhabitants would invite/abduct wastelanders to maintain genetic diversity (ala A Boy and His Dog).

  1. Practically

Before we begin, let’s consider a few things:

  • 50% chance the child will be female.
  • In its first years, Vault 68 can only produce 1 child/11 months.
  • Pregnancy related complications increase significantly after the 5th natural birth.
  • Generally, 1:67 births will be multiples. However, fertility drugs (if the vault has them) can raise that probability to 1:4.

Let’s say Eve enters a partnership with the Overseer and takes fertility drugs. Assuming she is pregnant as often as possible (as she realizes her position of power), 5 years later her family will look like this:


Now 30 years old, Eve will be at a higher risk of complications during natural birth. However, if needed, a C-Section birth significantly reduces that risk. Marriage arrangements can now be made with the security team to ensure the protection of Eve and her daughters.

16-18 years later (21-23 years after the vault was sealed), Eve’s daughters are married to the security staff. Because men remain fertile until death, they will be able to have children, despite the clear (and somewhat uncomfortable) age difference.


Now we have a few more families. Including Second Child’s sisters

32-34 years after the vault is sealed, assuming Eve’s three daughters all have five children each, there are now (on average) 7-8 daughters to distribute either to other security officers or the next lowest caste. Men who entered the vault in their 20s are now in their 50s and it is likely that Eve is no longer fertile.

Assuming similar birth rates, the third generation born in the vault will consist of 17-18 women. At this point, there will be roughly 30 women living in Vault 68, none of them inbred. As some of the lower caste men begin to age, the vault could create a sperm bank (odd as that sounds) to ensure genetic diversity if lower caste members die before the women trickle down to their level.

Where this model gets hairy is at the bottom. Once there are children in the lowest caste, the only place to go is up. Unfortunately, assuming monogamous relationships (fitting with Fallout’s 1950s motif and lifestyle), all children would eventually be related on some level. It appears that by the fourth  generation (65-70 years into the experiment) the only place for the lowest caste to go would be to the top caste (assuming every man in the vault had a wife at this point), so Eve’s sons (who would be 60-65 years old) would be married to their great great grand nieces, who they are 1/20th related to.


Once at the bottom, it looks like the only way to go is up.

Luckily, in Fallout canon, most vaults weren’t meant to stay closed for hundreds of years. Vault 68 could probably be opened around the third or fourth generation. With the door open and genetic isolation lifted, residents would be free to take in wastelanders or leave the vault altogether and form a new tribe. Either way, so long as the inhabitants of Vault 68 can avoid infighting for the first few decades, they have a good chance at survival. Although that could be the case, the world of Fallout is filled with deception, violence, and extremism, making it more likely that Eve’s existence would end up causing a war within the vault.

vault-boy couple fallout

One comment on “The Practicality of Vault 68: Trickle Down Genetics

  1. Dwellerfrom13 says:

    I would like to hear about the Trickle Down Genetics of vault 69.


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