The Source of Morality.

MORAL LAW... - Beliefnet
Humans are social animals and the behavioral imperatives or moral structures ultimately come from the local society(s) of which we are a part. Typically this is a religious society, and while the morals claim to be from God, each local parish or congregation has its own take on God's moral edicts. And woe be it to the member that violates any of these moral edicts, expressed or implied. While God's moral "absolutes" are theoretically universal, and applicable to all, in practice one congregation hates fags, one hates evolutionists, one hates all sex, etc. Even within God's realm one can pick and choose almost any moral structure one likes, just by looking at churches to belong to based on morality. Of course no one does. The milk church morality is the absolute morality of God.

Pardon him. Theodotus: he is a barbarian, and thinks that the customs of his tribe and island are the laws of nature.
George Bernard Shaw, Caesar and Cleopatra.

As one moves beyond ones church or village, it becomes necessary to choose among the society values including the morals of the various societies one comes in contact with. One's job will have one set, ones, church another, ones school still another set particularly if it is a public school (in the US.)

As one moves into the complex intertwined societies of the modern world it becomes necessary to be aware of the local moral structure so you don't violate it inadvertently. One may violate it intentionally or ignore it, but one must know why and how to cover up if necessary. From there it is an easy step for a thoughtful person to choose common moral structures "Love thy neighbor..." "Do unto others..." and less common ones that may be necessary for one's self respect.

Ultimately the people one chooses as herm society, people of compatible morality from work, church, school, and neighborhood, will determine the tribe from which morality is constructed. Note that the morality is the commonality from which one builds a society. But for reasonable people it is clear that morality is neither absolute nor universally applicable. That does not mean that for the individual it is not rigidly enforced. In the modern world one cannot afford to lose one's chosen social support structure, whatever that is, by compromising its mores.