I recently read a chapter in Hermann Kaiser's book "Ein Hundeleben" (A Dog's Life) about dog nutrition in the past. Although the dog has all the physical characteristics of a predator and is proven to have descended from the land predator wolf, in the course of its domestication it has developed into a type of omnivorous domestic pig. But not only that: many social classes were even encouraged to practice vegetarianism for centuries.
There is already evidence from Ancient Greece that the dogs kept at that time were fed cereal porridge and bread - because dogs fed exclusively with meat were observed by the ancient Greeks to be more "instinctive".
Even later, dogs were not exactly fed tons of meat. The hunting dogs of the medieval emperors were still legally allowed to eat meat from healthy animals, but this only applied to dogs with high ancestry. This privilege was stripped away in later eras to the extent that those noble hunting dogs were still entitled to part of the innards of their prey after a successful hunt, but this only affected the portion of the innards that could not be used in the kitchen. So the trash. On all other days of the year, the noble dogs had to satisfy with grain products - just like the majority of the underlings and their dogs.
As part of the so-called "Hundelege" (around 1500), the local farmers had to feed the noble hunters and their dogs; this was stipulated by law. Not exactly to the delight of the farmers, as one can imagine. Under certain conditions, the actual food for the dogs could also be provided in the form of grain deliveries - as a payment in kind, called "dog oats" and "dog rye". These terms show all too clearly that even the privileged hunting dogs at the time were viewed more as vegetarian porridge eaters than as carnivores. And at the rich tables of the upper nobility, they no longer cut meat out of the deer leg for their greyhounds - like 100 years before - but only cut off an edge of bread.
In the past, what was mainly fed was "Hundsbrod" (dog bread): "[...] poor bread baked from gluten and rye flour for the dogs" , although the proportion of inferior ingredients would certainly have been very different - depending on whether the recipient of the bread was a mutt from a farm or a noble hunting dog. In 1731, the residents of the German city Strickhausen were forced by paragraph 2 of the East Frisian hunting regulations to provide black bread and butter for the hunting dogs - black bread that was also part of the everyday food of the people there. Not to mention the butter. However, more ordinary hunting packs usually had to make do with cheaper barley bread, which was also made tasty with broth. Generally, two pounds of whole grain bread was considered the average daily ration per dog. However, this diet was and is in no way harmful to the dogs' health. Feeding trials at the Berlin Agricultural University that began in 1930 showed that rye is definitely suitable as a main food for dogs.
From the 19th century onwards, the staple food rye was replaced by potatoes (thanks to Frederick the Great's "Kartoffelbefehl" - "Potato Order"), which led to a significant easing of many supply problems within the population. The dog menu was expanded with the appearance of the potato and more and more dogs found, for example, a portion of stew on their "Lickebrett" (a board on which dogs and cats were served food), but of course only the vegetable portion without any meat. Back then, sausage was reserved exclusively for humans!
The changed conditions are also reflected in the feeding recommendations for dogs from the "Handbuch der gesamten Haustierzucht für Landwirthe" (Handbook of all pet breeding for farmers): "Dogs are generally easy to feed, which is why even some poor people can keep one or more dogs, since almost all of them are waste from the table or from the kitchen for his food. Others are fed with the meat of dead animals from the butcher's shops, others still receive bread, flour and meal, soup or mashed potatoes as food".  And in a book about dog training (from 1906) it is expressly recommended that dogs should be fed bread, broth or milk and some meat. 
Why this topic now? On the one hand, because a significant part of the dog population here in Germany is plagued by allergies and intolerances. Maybe our dogs are simply “over-cared for”? Maybe canned and dry food isn't as healthy as we're led to believe? Maybe a mixed diet based on the old way of dog-feeding would be more beneficial for their health? Questions upon questions...
Feeding your dog a lot of meat and few carbohydrates is generally considered very healthy. For this reason a lot of animals are barfed. I'm just wondering when exactly in the past dogs were fed so much meat since they joined humans? When did we have so much meat left over for our four-legged friends? One must not forget that the BARF fad is made possible by one factor in particular: factory farming - directly or indirectly. Without factory farming, the quantities of meat that are needed to feed people and (!) dogs with so much meat would not be available.
This topic is also close to my heart because there are certainly many people who are currently running out of money. The prices for dog food are rising all too significantly at the moment and some dog owners may already be wondering how they should feed their dogs in the future. So here's the good news: It's much easier and much cheaper to feed dogs. Simply cook for them and boom, done! The spices that humans need for taste are only added once the portion for the dogs has been tumbled or has already been fed. This saves a lot of money, it has proven itself over the centuries - and it probably tastes better to your dog than the overpriced canned crap. 😉
PS: You can find more information about how to keep your dog fed in my article “The dog's diet".
 Oekonomische Enzyklopädie volume 26, Berlin 1782, p. 467
 Dietrichs, J,.F.C.: "Handbuch der gesammten Hausthierzucht für Landwirthe", Leipzig 1848, p. 258
 Morgan, Tom: "Wie erziehe und dressiere ich meinen Hund?", Berlin 1906, p. 7 ff.