Theory:Caleb

- There are other evolved humans who alter their bodies - Danny Pine, Leona Mills, Perrin Crocker...

+ Danny Pine changed the composition of his body (from flesh to metal), not the fundamental shape of it. Leona Mills only changed her age, nothing else.

+ The only other abilities which caused their users to exhibit distinctly inhuman traits (Mohinder's ability, the elephant man's ability, and David's ability) were all granted by the uncatalyzed formula.

- All of those had constant and visible appearance mutations, Caleb's doesn't.

• Hence the part of the theory "but it was corrected or stabilized somehow".

- Mohinder's scales and slime were gone when he was exposed to the complete formula.

+ If a healer used their ability to try and help someone who has been injected with the incomplete formula, it might theoretically produce a 'middle ground' ability - not quite what they would get with the complete formula, but less dangerous than the original ability.

- If it were so easy, Mohinder wouldn't have needed the Catalyst to cure himself and his test subjects. And Arthur could find and assign a healer in the blink of an eye.

+ But then Arthur wouldn't have Mohinder at his beck and call.