ElloinmorninJ
Where'd That 6th Toe Come From?

So, for many years, there has been argument among fans, and even the original creators themselves, on how mutants were created. Tim Cain says "Radiation was the only factor involved in the creation of mutants like the rats, scorpions, and ghouls" while Chris Taylor said "Airborne FEV and Radiation were involved". Chris Avellone himself was subscribed to the latter theory for a while before switching sides, but, in my opinion, these two view points aren't mutually exclusive. Let me explain.
The main two arguments against the FEV+Radiation theory is that a) The creatures we say in Fallout's world, like Mantises, Scorpions, Rats, and Geckos can all breed, which goes against what the FEV is canonically known to do, and b) If airborne FEV caused all of this, why didn't it effect humans living on the surface in anyway?
Here's my theory: We already know that FEV was mutated and spread across the post-apocalyptic wasteland, so what I think happened is that this airborne FEV either mutated in a way to where it did not effect a victims sexual reproduction, or the FEV somehow effects humans and animals like Geckos and Radscorpions differently, similar to how the Intelligent Deathclaws in Vault 13 were never made sterile.
Likely, what happened was that the FEV itself isn't what created the mutants ITSELF, but what I believe happened is that it simply strengthened its host, so that they could mutate from radiation without just dying from cancer or tumors. The reason humans didn't mutate is because they actively avoided radioactive areas as much as possible, but humans on the surface still did get mutated by the FEV to an extent. Likely, I believe, higher immunity to radiation and more aggression, given all the raiders we see around. Also in the old games dwarves were common, so maybe that's more common.
But that's just a theory, a Fallout theory.
The main two arguments against the FEV+Radiation theory is that a) The creatures we say in Fallout's world, like Mantises, Scorpions, Rats, and Geckos can all breed, which goes against what the FEV is canonically known to do, and b) If airborne FEV caused all of this, why didn't it effect humans living on the surface in anyway?
Here's my theory: We already know that FEV was mutated and spread across the post-apocalyptic wasteland, so what I think happened is that this airborne FEV either mutated in a way to where it did not effect a victims sexual reproduction, or the FEV somehow effects humans and animals like Geckos and Radscorpions differently, similar to how the Intelligent Deathclaws in Vault 13 were never made sterile.
Likely, what happened was that the FEV itself isn't what created the mutants ITSELF, but what I believe happened is that it simply strengthened its host, so that they could mutate from radiation without just dying from cancer or tumors. The reason humans didn't mutate is because they actively avoided radioactive areas as much as possible, but humans on the surface still did get mutated by the FEV to an extent. Likely, I believe, higher immunity to radiation and more aggression, given all the raiders we see around. Also in the old games dwarves were common, so maybe that's more common.
But that's just a theory, a Fallout theory.