It's safe to assume that since Fawkes is intelligent that he was a prime normal. For those who don't know what that is. A prime normal is a human that has been exposed to as little radiation as possible. Like a vault dweller or Enclave member.

My question is. If Fawkes was an original member of Vault 87, where are the other vault dwellers that were transformed? I assume he was an original member cause he wears a vault jumpsuit. That I know of there are only two intelligent Super Mutants in DC.

When exploring the vault you can find experiments that could also be the other members of the vaults. You also find a lot of skeletons and that could point towards where they went. Other than that, some of them could have been transformed successfully into a super mutant.

I never fully explored Vault 87, since I found that place creepy. So I probably missed the skeletons, I do remember seeing the corpses of failed experiments though.

There's a room you go into where you'll see an extreme amount of skeletons on the floor. The place indeed is creepy.

I also forgot to take into consideration, that these were Mutants making new ones. According to Tabitha/Rhonda in New Vegas most of the dumb dumbs are 2nd generation or later. So it's safe to say the east coast mutants are 3rd generation, which makes them dumber than the rest. http://www.youtube.com/watch?v=4ZMwFORRC5E being the exception. Only the Master knew how to properly make Super Mutants, he did have a couple of dumb dumbs within his ranks like http://www.youtube.com/watch?v=jD1-qMdUNLE. But the Master knew that to make an effective Mutant like http://www.youtube.com/watch?v=Y97_Wz4fAtA in the original Fallout, Prime Normals were the key.

Even the ghouls in DC consider Super Mutants "Knuckle Draggers."