I don't believe that the person with the Hemophilia is more biologically fit than someone without the mutated gene, we have no mutated gene that offers any sort of advantage over being fit, I know it was I who before gave the example of Sickle Cell trait, .... it just so happens that African Americans are more affected by sickle cell than other types of anemia, and that confers some immunity against Malaria. but they don't have an advantage otherwise...their life expectancy isn't greater than a person who is biologically more fit!
.....I have not learned of a mutation that say will bring about an X men type of community of super humans or offer some sort of advantage ... mutations whether (nonsense, missense frameshift, small insertions/deletions, and one larger deletion) result in prematurely truncated proteins, either causing a disease state, cancer or death, but not an advantage certainly not newer species...