Morality merely a result of subjective passions of the desire to be integrated in family, getting laid, and protecting yourself / kin, and meet all the necessities of life. Example: You slept with you boyfriend/girlfriend (premarital sex), kill people who want to rob you, become a prostitute to feed your hungry family. Others said, "Premarital sex is immoral!" You said, "Fuck you! Mind your own damn business, sex is moral-ish & natural enough for me."
Morality is a result of social processes, intended to facilitate the survival of the group. Anything beyond that requires a belief in magic (religion). Atheists think out all the possibilities of everything that will make them survive. They don't depend on God.
I don't believe in morality. I don't kill, steal, or rape because rationality.
Morality is a subjective system that is entirely dependent on the society that produces it, and is therefore vulnerable to change and alteration. Hence, the morality of our primitive ancestors are not our morality--or at least, shouldn’t be our morality given that we are lot more intelligent than they were.