It's well known that dogs derived from a common ancestor shared with grey wolves roughly 20,000 or 40,000 years ago. Dogs self-domesticated as their ancestors followed hunter-gatherers, that is they domesticated themselves more and more as new, more docile generations were born. Today, dogs share 0.1% of their DNA with grey wolves. That sounds like a small number, right? So that means dogs ARE 99.9% wolves, right? Well, no, not really. That 0.1% has a huge impact on dogs. That is what enables them to digest starches, its what changes their brain structure and brain functions making them more sociable.
Modern dogs need a diet different than that of their carnivore relatives. They are descended from omnivores and need to be fed an omnivorous diet. Dogs evolved to eat potatoes and rice. Diet shaped their domestication. Dogs have genes that make a longer versions of maltase, an enzyme that is important in digesting starch. Longer maltase is found in herbivores and other omnivores suggesting it is important to plant-eaters.
Dogs that eat diets high in proteins and not enough grains are at high risk of kidney disease as the dog can't excrete urea well enough. There is solid literature showing diets high in protein and phosphorus are devastating to a dog's kidney function and can cause permanent kidney damage and death. One study showed renal lesion were more severe in the dogs fed a high protein diet than dogs fed a low protein diet. Another study showed dogs fed a high protein diet had reduced kidney function. Dogs even displayed more aggression and behavior problems when fed a high protein diet.