Animal Sacrifice and Substitutionary Atonement

I read the chapter entitled "African Religions" in Ari Goldman's The Search for God at Harvard.  I'd like to quote what Goldman says on page 223 about how reading and learning about the Nuer tribe (which is located in the Sudan) helped him to "better...understand [animal] sacrifice in the Jewish tradition" (page 223):

"The Nuer helped me understand.  By learning about their sacrificial rites, I was better able to understand sacrifice in the Jewish tradition.  For the Nuer, sacrifice is a way of substituting one life for another----the life of the animal for the life of a man who is in danger of death because of either illness or mortal sin.  In the ritual, the animal is killed, the blood is poured and some prime portions of meat are given to the priest.  Then the family that brought the offering sits down for a festive meal...In ancient Israel and among the Nuer, they kill for forgiveness----and then they eat."

According to Goldman, the Nuer regard animal sacrifices to be substitutionary, in that the animal dies in place of the person bringing the offering.  As a result, the person is forgiven.  That's essentially the concept of sacrifice with which I was raised: that the animal died in place of the sinner.  I one time heard preacher Ron Dart say in a sermon that animal sacrifices graphically got their point across, for, when a person saw the neck of the animal get sliced, he realized that he should have been the one who died, not the animal.

But there are other ideas that I have heard about animal sacrifices: that animal sacrifices were not substitutionary, but rather the life that was in the blood (Leviticus 17:11) put life into the cosmos (resulting in fertility), or that blood was a decontaminant that cleansed the defiled altar with life.  On a similar note, the belief that Jesus atoned for our sins in a substitutionary manner is only one Christian view on the atonement, for there is also the model that believers die with Jesus and rise again as righteous people, and other models, such as Christus Victor.

Who is right?  I don't know.  Could the Nuer have been influenced in their conception of sacrifice by a substitutionary Christian model of the atonement?  On page 220, Goldman talks about how African religion has been influenced by Christian missionaries.  In Malawi, people adored an ancestor named Mbona.  When European Christian missionaries came there in the 1800's, Goldman narrates, people in Malawi altered their conception of Mbona, saying that he was born of a virgin, and portraying him as a man on a cross rather than as a warrior.  Goldman's professor, Lamin Sanneh, said that "Missionaries did not disrupt [African religions, but t]hey added another layer" (Sanneh's words, except for what I add in the brackets).

But, according to Goldman, the Nuer were different, for they were "an isolated tribe of the southern Sudan" and did not come under Christianity's influence, "Despite the broad swath that Christianity cut across Africa" (page 222).  And yet, while I am far from being an expert on African religions, I'm uncomfortable with saying that Christianity could have had no influence at all on the Nuer.

But I wouldn't be surprised if the Nuer arrived at the conception that animal sacrifice was substitutionary on their own.  It's not that much of a stretch to arrive at that conception of animal sacrifice: the Nuer (like others) could have believed that sin resulted in death, and that the way for them to be forgiven was through an animal dying in their place.