how can mutations be good?

Answer 1

Species evolve mostly thru mutations.

Answer 2

Not usually. The two answers above describe that a particular mutation can help some people be immune to AIDS or malaria like sickle cell anemia, usually mutations caused by age or radiation or toxins such as agent orange are bad for the person" Whatever selective forces reduced the mutation rate in our distant past, at a time when most reproduction must have been very early, were not effective for older males.

I conclude that for a number of diseases the mutation rate increases with age and at a rate much faster than linear. This suggests that the greatest mutational health hazard in the human population at present is fertile old males. If males reproduced shortly after puberty (or the equivalent result were attained by early collection of sperm and cold storage for later use) the mutation rate could be greatly reduced. (I am not advocating this. For one thing, until many more diseases are studied, the generality of the conclusion is not established. Furthermore, one does not lightly suggest such socially disruptive procedures, even if there were a well-established health benefit.) " James F. Crow professor emeritus University of Wisconsin 1997

Answer 3

If a mutation is helpful then it allows the species to thrive. If humans evolved to be immune to Cancer, then that would be a good mutation. This happens in nature and it is called natural selection. Mutations are random and sometimes they help an animal survive longer and therefore are passed on to the offspring and if it was a great mutation then those offspring live longer and pass it to their offspring. If it was a bad mutation then the animal will probably die and not pass that trait along. So mutation doesn't mean a "bad" thing, it just means a change in a gene that isn't normal but it could be the best thing that ever happened for that species.