Maneaters
Consider this curious feature of the way we eat animals: unless you are a preening showman like Anthony Bourdain, you are always already a vegetarian of sorts relative to the vast majority of meats. You can't eat dog or rat or parakeet, even though these are perfectly reliable sources of calories. Arguments about the relative toughness or stringiness of their flesh do not get to the heart of the matter. You can't eat them because to do so would be to break the rules of the game. There are no such rules for the consumption of vegetable matter: whatever nourishes will do.
This distinction reveals something significant about meat eating: it is what you might call a charged domain of human activity, like sex and violence, and it is so no matter what kind of moral arguments you might offer up for or against culling deer herds, free range farming, and so on. Meat eating, like sex and violence, is regulated by religions, while for the most part plant-eating is not. Who can have sex with whom, or who can kill whom, or who can eat what meat when, are practically what religion is about. (The stuff about God is a later development, of interest to only a few.)
Why meat-eating should be seen as charged in this way, prior to any moral-philosophical considerations, is worth some reflection. It seems that at least from Porphyry on, the metaphysics and natural philosophy of nutrition required some sort of transformation in order to count as nutrition at all. That is, nutrition must involve at a minimum the transformation of matter that is non-identical with the matter of my corporeal substance into identical matter. Each creature then has a suitable range of non-identical food sources that it is able to convert into its own substance, but nature herself limits the range of possible conversions. Cannibalism would involve no conversion at all, and thus beyond its moral repulsiveness it is also naturally inefficacious as a source of nutrition. Thus the 2nd-century Chrisian apologist Athenagoras of Athens maintains that anthropopophagi, no matter how many human beings they eat, will gain no weight. "On the contrary, as soon as such meat, for which there is such a great antipathy, enters the space of the stomach, nature revolts and immediately eliminates it." "Nausea," Avramescu comments, "thus has an eschatological virtue."
