Human Sacrifice

In your research, I want you to list four factors:

Historically, when did such a practice begin?

In what societies is this practice most prevalent in, and do they still practice it today?
Why would a society decide to practice such acts if it goes against the cultural universal of morality? If Western societies find a practice immoral, why would others not feel the same way?
How do cultural anthropologists use cultural relativism to look past these practices, without judging these societies, when conducting fieldwork?