This is an odd topic, and I’m not sure what exactly put it into my head. Of course, once it was there, it stayed. So I had to write about it.
Cannibalism is a huge taboo in most human societies. People don’t normally resort to it unless they’re starving, and sometimes not even then. Shirley Conran’s Savages deals with four wealthy women being stranded on a tropical island and struggling to first survive and then sail back to civilization, but one of its most horrifying scenes focuses on what happens on the women’s boat once their food and water run out.
The child-eating Pale Man in Pan's Labyrinth is a terrifying figure, especially since it’s implied that despite the banquet spread out before him, he prefers to prey on children. But what if this practice, rather than being something resorted to in dire straits, is commonly accepted? What if everyone in a society does it?
Chances are, they’ll prey on those who are not members of that society – much like tribes which feast on their defeated enemies to either insult them even after death or to absorb their better qualities. You are what you eat, after all.
The Meewinks in Barbara Hambly’s Dragonsbane may simply have no other means of feeding themselves, since they’re small, frail-looking and wizened. Even their name sounds quaint rather than dangerous. But because of that, they easily deceive people who don’t know who they are, and they attack in a crowd of dozens, all starved and greedy.
Ritual anthropophagy, referred to as Sacrifice, occurs in Sharon Baker’s world of Naphar because the soil there is poor in the essential mineral selenium. People therefore recycle it by consuming flesh, an acceptable practice for them but not for offworlders who usually feel what the Napharese refer to as Revulsion.
“And that night I had my first Dream of Knives, and the other, the Dream of Meat that Speaks and Weeps. It’s common. There’s a joke--”
Quarreling, they met the dragon
Finally, Graham Masterton’s Feast depicts a cult which believes that the way to heaven is to permit others to feed upon you. And self-cannibalism is even rarer. Stephen King has a short story about a man who’s shipwrecked on a desert island and resorts to eating his own body parts to live. I don’t remember the title of that and don’t particularly want to; that crossed even my horror threshold.
When I first started reading role-playing gamebooks, the cannibals in them were painted savages dancing around a stewpot, but there’s more to the practice than this cliché. Cannibalism in speculative fiction nearly always produces a knee-jerk reaction of shock and disgust at first, but if a writer wants to develop it further (dare I say “flesh it out”?) it can add a unique aspect to alien societies.