Do good and evil exist and how do you define them?

[Skeptisk]

This came up in the recent thread about religion.

If you go back in time a billion years there were no multicellular life forms. In a world of single cell organisms it would be hard to argue that the concepts of good or evil made any sense or had any relevance. This clearly points to them being human creations, like pop music, French literature or Santa. Those are all things that exist in human culture but make no sense outside of it.

Accepting that they are products of culture,
could they be defined so that they would be accepted by all? I am not sure. It seems hard not to see them as relative terms. A lot of people would argue that the Nazis were evil, yet the Nazis didn’t see themselves as evil. Both sides in the Palestine/Israel conflict see themselves as good and the other side as evil (and both claiming supernatural support for their position…ironically from the same god).

If every person has their own version of good and evil could you take the majority position? Yet over history some things that were acceptable to the majority in the past (or even today in many countries) would be viewed as evil by many eg homophobia, beating of women, etc.