Well, those with a mutation in the MSTN gene don’t.Their muscles are already amped up, due to a lack of myostatin—a protein which tells the muscles when to stop growing.Animals who lack the protein often grow large, muscular bodies that contain very little fat.In humans, this mutation allows one to reach a muscle mass double that of the average person and stay muscular, without having to do much to keep it up.4.Uncanny flexibility

Javier Botet, a horror actor featured in the Spanish horror movie REC.Botet has Marfan syndrome.Marfan syndrome is a condition, caused by genetic mutation, where a person has less connective tissue than they should.Our connective tissue keeps our limbs, organs, and other body parts firmly in place.Those who have Marfan syndrome often have long limbs, piano fingers, and incredible flexibility.Javier Botet, mentioned above, has a mild variation, which allows him to put his body into strange poses—making him a perfect candidate for a horror movie.But those with more pronounced cases can experience severe, even life-threatening complications to their heart or other organs.