GEN631 According to [Rabbi Joseph] Albo, the logic of the passage [Genesis 8:20-9:6] is clear. Noah offers an animal sacrifice in thanksgiving for having survived the Flood [this verse]. God sees that human beings need this way of expressing themselves. They are genetically predisposed to violence (“every inclination of his heart is evil from childhood “). If society were to survive, humans would need to be able to direct their violence toward non-human animals, whether as food or sacrificial offerings. The crucial line to be drawn is between human and non-human. The permission to kill animals is accompanied by an absolute prohibition against killing human beings, “For in the image of God has God made man.” It is not that God approves of killing animals, weather for sacrifice or food, but that to deny this to human beings, given their genetic predisposition to bloodshed, is utopian. It is not for now but for the end of days. Until then, the least bad solution is to let people kill animals rather than murder their fellow humans. [On why God never chooses to change human nature, see Rambam, The Guide for the Perplexed, III:32].  Sacrifices are a substitute for violence directed against mankind. SACKS 160-1