@Rockhead,
I know there are cases of women who kill their child(ren) to get back at the father, but to have numerous members of a society agree to do this seems beyond mentally ill. Of course, the Aztecs and Mayans routinely killed their offspring as sacrifices to their gods. I remember reading how one god craved the tears of children about to slaughtered so their tears were caught in ritual cups made just for the purpose. Humans sometimes stun me.