ummm actually super mutants were created in vault 87
Yea, I Know.
Listen:
In Fall out 1, There was a man who was knocked into a FEV tank and formed into some mutant type creature, after months surviving by absorbing things and making his IQ jump up each time he absorbs. He then got bored of that and decided to Test with this FEV Virus and instead of Absorbing people who wonder into the base he decided to Dip them into FEV with dogs, rats and all sorts which forms many types of Mutants like Centaurs ect.
He dipped in many humans and they all lost there minds after being dipped, Some managed to keep there Intellegence but few did. After that The Master Formed his own army of super Mutants with that came lots of normal people to worship him like a god they found them selves as "Children of the Cathedral" So he could get his ideas and beliefs around the HUB and then the world (hehe).
After this a man named The Vault Dweller was orderd by his Overseer to find The Master and kill him to stop the mutant threat on Vault 13. He did that and killed the master this ending the threat, But that was wrong.
Three groups formed from the mutants Some went to D.C, Some just wondered around and the others stayed to fight in California but died out.
The Mutants found a area which tested in FEV (Vault 87) and decided to use that as there breading ground.