A humanity in which eating a slain animal is a sacred act and cannibalism even more so, in fact has been for as long as anybody can remember  Of course there are parasites, but humans have had time to coevolve and breed symbionts to keep more malicious parasites and prions at bay  Eating someone, you become part of their extended family, host the same guests the rest of the family shares, sometimes jealously protects  Symbionts that produce certain vitamins, stimulate muscle growth, protect against diseases, repel mosquitoes, heighten the mood  Add magic to the mix: certain symbionts grant magical powers. Wizards, to be less tasty and not be hunted down, eat disfiguring parasites  "Great power comes at great cost" - like being the equivalent of a leper. Children aren't considered persons until they've consumed flesh:  Some are used in experiments to separate the power-symbionts of great wizards from their parasites, killed if they don't catch symbionts  Some symbionts are incompatible - it is a complicated science to find just the right combinations and some paraethnicities form around that  Be too eclectic and a bad interaction may kill you Cities where they put citizenship-symbionts in the water supply and foodThe initial thought process went roughly like this: "Okay you can (among other things) be a vegetarian out of empathy, or a carnivore out of lack of empathy. What if you're a carnivore out of empathy and celebrate eating your prey's flesh and souls? In fact, what if you went ALL the way? What if a society went there?" These people started out as baseline humans, but became cannibals along the way. Maybe they were in a population bottleneck or a really weird but successful religion happened, or the zombies won the apocalypse. Either way, eating other people is now normal, even celebrated, and has been a tradition for at least thousands of years. Of course, parasite load is huge. Something must've happened to these people that makes them immune to prion diseases, maybe genetic immunity or their first major parasite producing enzymes against certain classes of prions. To the other parasites, they adapt in the traditional ways: genetic traits (slow) and cultural practices like special diets (a bit quicker). There is now a third way of passing on phenotypic information: Ingestion. You eat someone to gain their powers and it is not a superstition this time. Families are as much defined by blood relationships as they are by parasite relationships. Para-marriage is the process of eating a deceased family member to get a stomach full of the family's parasites. Humans carry parasites and symbionts and have rich strategies for dealing with either. Symbionts provide vitamins, drugs, prevent certain diseases, keep out other parasites, make you poisonous to predators, glow in the dark or just make pretty green patterns on your skin. Some are incompatible and will produce severe allergic reactions in the host if combined - don't just combine them willy-nilly. Unless you know a third guest that will reconcile the two? Para-marriage is a finicky and complex business. Some symbionts do nearly nothing and are used as markers of affiliation, for example by cities to put in water supplies: An incompatibility could be bred in on purpose to keep foreigners segregated. Experimenting with parasites is commonplace and necessary to filter out deadly ones early - for this purpose, children are bred. If they survive childhood, their parasite makeup is good and healthy and they gain personhood. If they don't, they needed to die anyway. Monks: Some people trade in their fertility for certain symbionts. They still have two other avenues or passing on their legacy, so it's not too bad a bargain. Magic (optional): some symbionts carry magical powers. These are extremely coveted, so magi take care to either not look like magi, or be unappetizing corresponding to their powers by carrying actually detrimental parasites - anybody who eats them to gain power will also gain these parasites. If you have the resources, you can attempt to separate parasite from magus-symbiont, all you need is a ton of children and at least one to be infected only by the symbiont. Why are you looking at me like that? They aren't persons yet. Only if you die a person, you deserve to be eaten. Considering how even two dimensions of inheritance weird up things, I don't think this is nearly exhaustive. This is a a system with extremely many parameters and I don't think I can fully map this out just now. But given an intelligent species and a will to self-modify, it's probably quite survivable. published: Sep 02 2016. epistemic status: subjunctive.