The eating each other's babies thing is what you get when group selection doesn't appear.

Is that right? I may be misremembering, but I thought that the eating babies thing was a result of group selection. Eating babies arose when a group was under group-selection pressure to have a smaller population. The group complied with the pressure by having individuals within the group consume babies within the group. It was just that the individuals ate the babies of other individuals, thereby acting in accord with both the group-selection pressure and with an individual-selection pressure.