It's always interesting to see stories like this about the possibilities built into the human body at base level. You hear about cross-breeding of animals, designer babies, mutations, and evolutions but one thing seems to have been evident throughout all these scenrarios. While there is tremendous ability in living things to alter and adapt, they are all still the same type of living thing. we haven't, for example, actually seen or accurately recorded a evolution of a reptile to a bird or a monkey to a human. If anything, history and science have shown that while certain abnormalities may occur, those abnormalities present danger to those who have them. In the example of the "super baby" (linked in the title), it has all this strength but because of the defect that allows those muscles to grow so much, the baby will likely have heart problems among other things that could threaten and shorten it's life.
There are positive things that come out of examples like this, medicines or cures for ailments like muscular dystrophy and possibly even AIDS or diabetes are listed. All in all, it's clear to me that our bodies are made with great flexibility but within a certain set of limits. No true X-Men scenario would be in any way likely.