wizard magazine asked a havard biologist whether mutation could give people powers or not on page 22 of issue 158 (dec 2004). in a nutshell, her answer was no, mutation usually only happens in one cell and is either unnoticable or negative. she did say, however, that genetic manipulation might yield powers if you could copy a naturally occuring ability from an animal or some such.
did anyone read that book "arm of the starfish" ? i think that applies.