I asked G+ if an obligate Carnivorous species could ever develop a city-based society, and I got a loooot of answers. I've compiled the best responses below and tried to arrange them by general theme.
This means some peoples arguments and points got chopped up a little. It's worth taking a look at the thread. It's public and you can find it HERE.
Zzarchov Kowalski - "It is 100% to have a carnivorous species survive using agriculture, by growing plants to feed livestock. It would certainly need to be very efficient and it would have fewer specialists for technological improvement (perhaps requiring conquest or trade or enslaving omnivore species). But lets do the math.
High end grains can get 10 million to 15 million calories per acre (rice, corn and potatoes for vegetables), while low end like wheat is about 4 million.
A pig will need about 910-915 thousand calories to produce about 200 thousand calories, or 1/5th efficiency. Pigs are about 3.5 million calories per acre.
So an Acre of Corn/Potatoes and an Acre of Pigs (one of the more calorie efficient livestock) would equal what another culture could do with an acre of wheat.
So Humans with Wheat living would have twice as much food as say Cat People who farm corn and pigs and thus have far more non-farmer craftspeople, artists and researchers.
If they lived next to each other, they humans would quickly steal corn and shoot way into the lead (unless instead of Corn and Pigs it was some noxious weed that can only be eaten by giant grubs which just happen to be the same as corn and pigs for calories)."
Timothy Linward - "There might be obligate carnivore ant species. I struggle to think of obligate carnivore social mammals - wolves and baboons both being omnivores with a meat preference. So the development of social structures at all seems a leap. Then again, could an ethnologist tell us if Inuit have (had) cities? (I'm assuming that the Inuit diet is all based on seals, whales, fish and birds, I could well be mistaken.)"
Aaron Parr - "A pure meat eater has to eat almost 10 times as much as an herbivore for the same amount of energy. You lose 50% - 90% of the energy each time you go up a trophic level in the "food chain". So in reality a civilization of a purely carnivorous species would be destroyed by a competing omnivorous species because they would lack the numbers.
But maybe if they were smaller and smarter and had another edge... they'd still dominate."
Dave R - "Note that nomadic pastoralism (herding) can support a people on a carnivorous diet.
Note too there's an argument that the very first settlements preceded agriculture, that sites such as Göbekli Tepe and Nevali Çori were built by hunter-gatherers as religious or ritual gathering places. Settling them year-round came later, and agriculture came later still.
Substitute herders for hunter-gatherers building a central religious site that only gradually becomes occupied year round and you're there. Population density is still a problem. I think you'd have to stipulate only the priest caste and their servants would count as a settled city, with tribes of herdsbeings making periodic pilgrimages to the center.
I can make a stronger case for carnivorous sentients becoming herders in the first place. Herding can grow out of hunting, without any detour through farming."
Jacob Hurst - "One other possibility could be a fully mobile nomadic civilization that controls huge territory in order to follow the ever mobile migrating creatures on which they feed. Perhaps this is the reason for the traveling fey seasonal courts?"
Gregor Vuga - "It would be possible if there was a great aboundance of wildlife to hunt as well. The earliest civilizations formed around agriculture but many of the earliest societies formed around river deltas where there was lots of fowl and game as well as fish, crabs etc."
John Bell - "Possibly. Fishing or foraging for insects might be sufficient, especially if they cultivated them. You would probably see a lot of smaller, fast-breeding animals with small agricultural footprints, like guinea pigs, rats, chickens, etc. form the bulk of the food source, rather than cows, deer, etc."
Scrap Princess - "what about something like buffalo herds? Massive populations grazing even greater landmasses?"
"like the Inuit lived primary of meat right so you just have to have a situation where everything they were catching was more calorific by several magnitudes? Like if we say a Innuit community was about 100 people if was doing okay and ye olde city is 10,000 , the seals and whales just need to be 100 times the size"
Justin Akkerman - "What about something like the salmon runs of the Pacific Northwest? Massive hit of calories once a year that gets smoked and preserved that allows the support of a more complex society than would otherwise be possible"
Scrap Princess - "Yeah if you include insects it's plausible right? Like something like mealworms or compost worms that can eat garbage and double their population in a month or so?
Also rotting things can make more nutrients available from otherwise undigestible material like bone or cellulose.
Humans haven't made a bone sauerkraut but it's not to say some fantasy race wouldn't.
Apparently it's one of the reasons dogs bury bones "
Jacob Hurst - "They could also be farming fish or insects like crickets/meal worms like +Scrap Princess? said. Could bee living around some sci-fi relic that's basically a self contained ecosystem that starts with something like algae and spits out pure protein bars at the other end. Like they sorta did in Snowpiercer.
That way daily consumption is accounted for and "fresh meat" is thus more of a special thing."
"Or maybe they've tapped the breasts of some sleeping mother of monsters, and their diet is basically 100% dairy"
Dan D - "Give them meat-plants and they'll be good to go."
Chris Tamm - "ants have done it - hunting more viable in warmer wet climates and can support huge populations, stealing young and fattening them is the start of agriculture and more sophisticated and deliberate herding would happen.
Someone has taught apes to breed birds and steal their eggs deliberately. Insect harvesting could be viable - one of easiest protein sources and breeding larvae was done by aztecs - people have done this in desperation or novelty mostly but it works. i always having bugs harvest your crops for you would be good, bugs eat crops then you eat them
aztec aquaculture bred fix, axolotls, grubs, ducks and all kinds of critters out of desperation for protein. The carnivorites would grow plants for their animals and livestock. Eventually they breed something that likes being kept in a dark box getting all it can eat. Eskimos struggle to get more diversity than barley and seaweed for non meat. Carnivores do nibble some greens and berries and eat the vegetable matter in the guts of animals. Perhaps feeding a creature tasty herbs then killing them and eating them.
they could just worship the meat god who gives them more meat than they could ever use""
Matthew Adams - "Genetically manipulated meatbags (beeffalo, or buffedalo, roaming the plains)
Factory farms supporting factory farms. For example factory farming meal worms and crickets which become the feed for chicken or pig factory farms. Feeding the meal worms or crickets might require agriculture performed by an untouchable caste, or instead of meal worms or crickets they use maggots implanted in the dead (no cemeteries, just bone houses)."
Aaron Parr - "It is possible but tricky. For land based food production, you'd need a really impressive culture and religion and economy at the center to draw all those pastorialists in for the slaughter of their animals near the central city hub.
But with really rich seas it would be more likely as you can have a port city and lots of fishing from there. Growing herbivorous fish (like tilapia) in aquaculture tanks also produces a lot of protein from the power of the sun and adding processed sewage to the water. Sounds nasty but in a 3 part processing system this works really well, efficiently and is very productive.
So for the fantasy angle I would go with an amphibious humanoid that likes to eat giant squid and whales, and builds cities on the sea shore. They are social because their prey is so big that it requires organized hunting efforts of many individuals. Since carnivorous beings benefit less from population density they would also need a really rich and amazing culture to maintain a large population center with specialized niches in the economy. Some say this is true for humans as well... all that city culture has to be enough of a pull to offset the downside of crowded conditions, cholera etc...."
Lord Mhor - "This would be particularly efficient if one of their enslaved food species was itself intelligent enough to engage in its own agriculture, and could feed itself before in turn being harvested for meat."
WHAT WOULD THEY BE LIKE?
Connor W - "As others have noted yes, but with these further stipulations:
-Much smaller populations, like 1/10 the size (simple application of the trophic level "rule of ten")
-Arguably more advanced social capacity. Cooperative hunting would require complex social structures like language early.
-There is a theory that when humans became omnivores and ate more meat the protien density allowed for much larger brain sizes
So super smart, very socially complex small societies.
"Perhaps initially physically more impressive, but as they have developed a society they have gotten less dependant on their bodies (like us).
Definitely lazy though, think of lions that live in zoos."
Kyle Latino - "If they were cold blooded and/or hibernated for a season or two a year, I think it would be plausible enough."
Jacob Hurst - "Perhaps may also have a structured/ritualuzed fasting regime that's deeply ingrained in their culture. Not everyone needs to eat every day, or perhaps even every week for some carnivores.
Maybe that's when the specialized work/art/research is done? During the fast."
Claytonian JP - "Vampires. The oldest ones are apes that uplifted the rest of us inadvertently at first, then purposefully later.
Matthew Adams - "+Lord Mhor's vampire aliens using religious indoctrination to control the herds. When men reach the age of thirty, and women the age of thirty five, they enter the pyramid for a month, and emerge as these super scary carnivorous beings that are beautiful to look at. They rule over the younglings who believe these beings are their loved ones transformed when in reality the younglings are consumed or butchered in the pyramid and a member of the super intelligent carnivore race emerges from the underground nursery to replace the meat. Logan's Run on weird drugs."
Gus L - "What about a carnivorous plant people? They'd need far fewer calories of meat, as the could still photosynthesize. Meat just becomes a source of extra energy and minerals?
I think it'd work for lizard/snake people as well - they would lay around a lot saving energy while the crops grow to feed their food."
What would it be like?
World of Natural Abundance
It would probably need to start out with more meat than our world. I don't know exactly how much of the planetary biomass has been in the form of meat over history, I tend to imagine Dinosaur times and Pleistocene times as being more meaty as they have all those megafauna, but that could just be a smaller number of bigger animals.
But lets go with Megafauna as the idea of them has more poetry, a world of BIG Dinosaurs, Giant Sloths, Moa, giant seal-things, big Whales and etc.
Our predator civilisation probably started out as predator nomads and only slowly settled down.
If humans and the predators co-existed at the same time then possibly humans would have become civilised first and the predators would have been the ultra-terrifying Barbarian hordes from a D&D game.
But, if they genuinely did exist in the same ecosystem for a long time then the effects of intelligent predation on human development are almost impossible to predict. We might be a very different species. We might even think that being eaten was natural, or even good (see below).
Almost everyone agrees that a Predator City would have to be a fucking amazing place to be, simply in order to attract the numbers of pastoralists and other types they need to supply food.
Think here of something like a Super-Byzantium. Better and more beautiful art. More and better philosophy. Bigger libraries with more knowledge. More beautiful, poetic, coherent and transcendent religion or religions.
Going to this place or being allowed to live there would be almost sensorily overwhelming to a standard human. In the global culture it would simply be *the* place, the place of places, like a New York of New Yorks, the place that stories are set, that we expect decisions to be made, the super-creative, super-compelling hyper-city, almost a place of dreams, as well of nightmares as it runs directly on blood.
A lot of commentators think the intelligent predator species would need some kind of an edge over an omnivorous generalise like Homo Sapien and the usual genre possibilities are brought up, but the simplest is simply that they might be more intelligent.
What if this species had an average IQ of 150?
Assume they are a little bigger and a little stronger than us as well. But the main thing is intelligence.
The average member of this society would be in the top percentile for Homo Sapiens. One of their stupider members would be standard for us. A smart one would be nearly incomprehensible.
If we evolved alongside them we would probably worship them as near-angelic beings, closer to whatever the godhead was because they prove themselves physically and intellectually our superiors in every way, relentlessly.
We might not even both asking complex questions of each other, we would just ask them and Homo Sapiens resources would be dedicated not to finding stuff out, but to getting access to the Predator Culture.
A Meat God
We would probably, generally, think it was OK, or at least not immoral that they eat us. After all, we eat pigs and whatever because we are smarter and better than they are, in contact with a species that we were certain was better than we were, we would probably think it reasonable that they eat us.
This probably wouldn't be warfare, just a quasi-slave situation. We might feed them low-status people, in some cultures high-status people might fight for the right to be eaten by them, or to sacrifice family members to them (to get closer access).
Like Matthew says, we would all probably worship a Meat God. The God of Abraham is pretty much a Pastoral Herder God. The fact that the Priests of the Meat God were genuinely more insightful, more penetrating, that their scripture was more transcendent than anything we could come up with, means we would probably just go along with it.
Strange Forms of Forced Abundance
This increadible sacred hyper-culture based largely around, maybe one single city, or maybe a handful, would have developed a huge number of strange agricultural methods to produce protien.
Stealing from the above comments;
INSECTS - Growing larvae on pretty much anything. Giant insect farms. Using insect swarms as harvesters - send out the specially bred locusts to eat the grain, when they come back, eat them.
AQUACULTURE - A huge area of complex fish and amphibian farming. Like the artificial islands around the Aztec Captial but extended with artificial deltas, dug lakes, a level of buily hydro-geology greater than the Chinese River Valley civilisations but dedicated to animals rather than rice.
MEGA-BREEDING - Gotta keep those giant mega-fauna from the pastoral era around to feed high-status individuals. Brontosaur and Mastodon herds guarded by specific Homo Sapiens clans. Moa herds, Hippo herding (losses are acceptable).
CONSTRUCTED MEAT WEBS - This is probably, in real terms, the most inefficient and unlikely method for actually providing calories, but I have become enamoured of the dark poetry of it, and it would be really good for storytelling and gaming. So, monkey trained to steal eggs. can we extend that idea? Homo Predator managing Homo Sapiens who rule over Homo Florensis who farm the Guinea Pigs in the walls of the Predators Castles. Birds trained to bring the locusts that fed on the crops. Partnerships with Killer Whales to herd oceanic megafauna.
The thing with this predator-ruled world is that, like its ruling city, it would be both a dream and a nightmare.
With a small dominant species with a very high IQ controlling everything, centralised government would be easier to arrange. Since they would depend deeply on interconnected food webs they would pay a huge amount of attention to the stability and sustainability of the environment. They would be gardeners of the planet, much more than Homo Sapiens.
And culture would be genuinely better, more advanced, more refined, more coherent, more spiritually fulfilling, perhaps more scientifically and theoretically advanced with less futile mistakes and fewer catastrophes.
And we would be high-status prey organisms. We would be food and we would probably think that was fine, and from a very distant viewpoint, we might be right.