Is the double muscling mutation in cows considered a harmful, beneficial, or neutral mutation?
It's beneficial for us; not for the cattle. Humans can also get this mutation and it is treated as a genetic disease.
Consider each choice one by one Harmful mutation - Yes, in the natural environment the animal is less fit. However, the natural environment has dwindled and does not exist anymore, so the first choice is ruled out. Beneficial mutation - The animal is more fit. Yes. In the man-made shelters, these animals do better. Neutral - No. The animal does have significant change in its form. Yes. The animal is fit for its man-made environment and can successfully survive. Science - Myostatin gene deletion: First described in cattle as “bovine muscular hypertrophy” by the British farmer H. Culley in 1807. Cattle that have a myostatin gene deletion look unusually and excessively muscular. Follistatin blocks the action of myostatin. Aside into the comic world. Perhaps the radiation from our yellow sun activated some epigenetic mechanism that eventually led to increased follistatin expression in all the muscles in Clark Kent’s body. Voila. Super-strength. Krypton would null this superman power.