I'm not going to dispute that, because that is what I was always taught. I read a study (on the Kuru) that suggests that certain tribal populations certainly practiced it either ritualistically or when faced with starvation. This leads some to conclude that while cannibalism is universally prohibited now, it was not always thus. IOW's the religious prohibitions grew out of an earlier period where the practice was more common.
I disagree. I don't think that religion has anything to do with it. I think it goes against nature. Even the Incas, Aztecs, Mayans, etc were brutal (decapitations and ripping hearts out of thousands every year), there is almost no evidence of cannibalism.
Only on certain Polynesian and Pacific islands was it practiced for any great length of time, and that (it is believed) is because of isolation. On the continents, there is very little evidence of cannibalism.
One professor had the theory that it caused family units to draw closer, only eating outsiders. This let to in-breeding, which will destroy a civilization pretty quickly.
It almost never happens in the natural world, at least with mammals.