Where does ethics come from?

I’m sure this question has been asked here before, but it didn’t come up in the first 3 pages of search results or as a phrase.

Paul Ehrlich said (paraphrasing) there are 3 main beliefs:

1. There exists a universe of ethics independent of the universe in which we live. Or, equivalently, there is a god with all of the answers.
2. Ethics can be derived directly from the evolutionary process itself—basically, whatever behavior has evolved is good because it evolved, i.e. “naturalistic fallacy” (I think both in the “appeal to nature” sense and Moore’s original semantic definition, although Ehrlich doesn’t differentiate).
3. There is no extrinsic source of ethics. Humans have evolved the capacity to hold and share values, but natural selection has not helped us in deciding what values to hold. The content of ethical systems is a product of cultural evolution.*

Do you subscribe to any of these? If so, why? If not, what is your view?

I’m inclined to agree with the author on #3, except that I can’t totally accept the claim that natural selection and ethics are totally separate matters. While the anti-gay sentiment would be an easy argument in favor of this claim, cannibalism would seem to be an obvious opponent. People obviously mostly agree cannibalism is morally wrong, and mad cow disease is an example of what can happen as a result of it. One could argue then that through evolution a “do not eat your own kind” rule was created to better ensure survival.

Ehrlich argues that “Genes cannot incorporate enough instructions into the brain’s structure to program an appropriate reaction to every conceivable behavioral situation, or even very large numbers of them.” However, I believe Dawkins (for one, there are probably others) suggested that as a computer programmer writing code would not be able to anticipate every scenario possible but would be able to provide a basic set of rules as a starting point from which the program can learn, so could genes do the same.