I had a friend claim that morality and "survival of the fittest" creates a problem. This is only so when you think one dimensionally at what is meant by "survival of the fittest." Survival of the fittest does not mean that the literal strongest survive. It means the animals that are most fit for survival survive. For instance cheetahs use their speed to survive and the fastest of them are more likely to survive. Other animals may actually use their strength to survive. The strongest of them tend to survive. Are humans a strong animal, not really in comparison, are humans a fast animal, definitely not. What then causes us to survive?
Lets explore this for a moment. We like many animals are social animals. Between being social and communication we have surpassed all other animals in ability to survive. Now, social animals must work together to survive. The animals that work together and don't cause problems are the best at survival. This is where morality comes in. Morality is doing what is right by other people. This benefits our survival. Who was more likely to survive when civilization was beginning a person who worked with others or the person who did bad things to the others. That person would be shunned out and was less likely to survive on his own.
So we are seeing that this helps individuals and the entire species to survive. So actually our own survival is a good reason to be moral and very well could be where morality comes from. As humans we have learned how to communicate as well, so that increases the common understanding of morality, adding to our ability to survive.
This explanation also explains why morality has changed. It has evolved, because we have learned certain actions benefit society and certain ones don't As we learn this we create rules of thumb in terms of morality and live by them which make us more likely to survive. Now being we a lot of the times are using rules of thumb in regards to morality, issues can come up that make for moral issues. If two rules of thumb contradict, or if a rule of thumb actually doesn't benefit survival in a certain time, we may experience problems. But these rules of thumb benefit, because an overwhelming amount of times they do work towards helping us to survive.
Now I admit this contains one assumption, that we have a will to survive, and animals that have a will to survive are more capable of surviving as they avoid death. Where this will to survive came from is irrelevant to this argument, as the argument was morality can't come from "survival of the fittest" or evolution? Now go ahead and pull the old infinite regress into god the gaps fallacy on the instinct to survive.