Right and wrong are subjective to the culture we live in. The tree in the bible is not literal truth, but it was a really good way of describing what happened to people who were absolutely ignorant, and who needed guidance. The tree was the tree of knowledge of what right and wrong really is. We metaphorically ate that fruit. (literally evolved our cortex). That doesn't mean we suddenly and intuitively knew right from wrong- we would still be in the garden of eden if that was what the metaphorical fruit did. The knowledge that we learned-, the knowledge that forever separated us from the rest of the animals is, that right and wrong are not absolutes, but vary and change according to needs, who is in charge and who is backing you up. The current theory in developmental psychology is we are born with no morals at all including animals- nothing, and we learn morals through observation and experience in the culture we live in- but monkeys and dogs do this too. The difference is humans know it's a paradox, that right and wrong can depend on which side of a fence you are on, that those that we know for sure are absolutely in the wrong are also in their own eyes completely in the right. That paradox can lead to prevarication, side swapping, and even nihilism, hence the almost global reliance on religion. Without it we would never get any killing done.