The original idea of human/animal sacrifice was you gave a human/animal as a gift to the god of field fertility. You burned the body to turn it into smoke to waft the gift up to where the god was resting where he could enjoy it. He would be so pleased and he would make the fields fertile. This sort of worked, because if the ashes of the sacrificial victim were spread on the fields, they acted as fertiliser. The priests did not realise you could get much better effects with cattle dung.
This morphed into the idea that if you sacrifice a human or animal, with magic ceremonies, the guilt in you could be sucked out and transferred to the sacrificial victim. When they died, the harm of your sins would be magically erased. This is similar to Catholic indulgences, but without the sacrifice, where by paying a fee, the church would perform some magic to erase the effects of your sins. This was a con. There is no magic you can perform to undo the effects of a rape or murder.
What is so bizarre is people living to day still believe in this mumbo-jumbo when it involves the human sacrifice of Jesus.~ Roedy (1948-02-04 age:70)