1 As you get older, your risk of a rotator cuff injury increases. Rotator cuff tears are most common in people older than 40.  Certain sports. Athletes who regularly use repetitive arm motions, such as baseball pitchers, archers and tennis players, have a greater risk of having a rotator cuff injury.
Evolution by natural selection is one of the best substantiated theories in the history of science, supported by evidence from a wide variety of scientific disciplines, including paleontology, geology, genetics and developmental biology.
Natural selection selects those genetic mutations that make the organism most suited to its environment and therefore more likely to survive and reproduce. In this way, animals of the same species who end up in different environments can evolve in completely different ways.