Isn't it odd how the biblical deity like the many deities believed before him share so many things in common? But the one thing they all seem to share is that most of them desired blood sacrifices. For some of the so called pagan deities the blood of animals was enough to appease them temporarily, this was also true of the biblical deity as well. For others the sacrificing of people was the only thing that satisfied them.
When God decided to institute the system of sacrifices he laid out specific rules that had to be followed by the people and the priests. The animals could not have any blemish whatsoever and they had to be of a specific type of animal, there were what God considered clean and unclean animals. They had to be sacrificed at specific times of the year for specific purposes. But according to the N.T. these sacrifices only temporarily covered the sins of those that made them. It did not wipe away the sins completely.
In order to wipe away sin completely the sacrifice had to be perfect and without sin. Christianity provides for this through the sacrifice of Jesus Christ once and for all. They even refer to the O.T. system of blood atonement as a type of what was to come in the most perfect sacrifice of all: Jesus Christ the son of God. But if you read your bible carefully you will find out that Jesus was not the only human sacrifice the deity accepted.
In the O.T. there is a tale of a man named Jephthah who made a vow unto God where if he was given the victory over the Ammonites the first person that met him upon returning to his house he would sacrifice. It turned out to be his only daughter and in the end he had to do as he had vowed. You can read all about it in Judges 11:30-40. At times the bible mentions other groups whose deities required blood sacrifices.
All of this points me to believe that the institution of religion and the concept of God itself are all rooted in myths based on ignorance and superstition. People refer to the idea of God evolving but apparently he has not evolved much. He still loves the fragrance of blood. And even in Christianity it is only through the mythical blood pact of Christ that you can be saved.