I think morals and ethics evolve. Like biologically evolved traits, some morals are better adaptations than others.
Eyes are not universal in the animal kingdom. But they’ve evolved independently about 40 times. Animals with eyes, with only a few exceptions, tend to be better off than animals without eyes. Having eyes, in terms of natural selection, just seems like a really good idea.
The same exact idea applies to morals in human society. Laws against murder, for example, are not universal (murder is a big problem in undeveloped tribes), but they are very common, and this is because they are a good adaptation for a society to have. A society where murder is enforced against is going to be much more stable than a society where grudge killings, for instance, are allowed.
Other examples are laws against stealing and adultery, laws governing “torts,” and moral principles encouraging altruism and social sacrifice. Societies with these ideas are going to have a better chance of surviving—and, consequently, of spreading these ideas—than societies without them.
That said, human society is not a static thing. Just as animal traits adapt to changing environments, human morals do (and should!) adapt to our changing society and world. One obvious example are ancient laws regarding adultery. In old societies, women could not work and were considered to be an economic burden, so “marriage” was an economic arrangement where a husband basically purchases a wife from her father. Since women were conceived of as essentially property, adultery was akin to stealing (it was also only defined from a male perspective—women always commit adultery out of wedlock, but men only commit adultery if they’re sleeping with another man’s wife).
Today, our society has evolved. The development of technology now allows women to make money, so the concept of marriage as an economic arrangement is a vestige. The idea of romantic love is also a relatively new development, refocusing marriage as a personal relationship rather than as an economic contract. For this reason, while I still think adultery is wrong, I don’t think it makes sense to enforce laws against it or punish people who commit it. Society has evolved, and our morals about adultery ought to evolve with it.
Another example is the concept of property. What will property mean in 50 years when everything valuable is essentially information that can be easily copied and pasted? I honestly don’t know.