The claim that dogs are simply wolves, and should eat accordingly, runs into a specific genetic difficulty. Their starch-handling machinery diverged measurably during domestication.
The enzyme that starts the process
Breaking down starch begins with amylase, which cuts long chains into smaller units the intestine can process further.
Dogs produce this enzyme in the pancreas rather than the saliva, so digestion of starch begins in the small intestine rather than in the mouth.
The gene for it is present in wolves too. What differs is how many copies each animal carries.
Gene copy number as the difference
Wolves carry a low and fairly consistent number of copies of the amylase gene. Domestic dogs typically carry considerably more, and the range across breeds is wide.
More copies mean more enzyme produced, and more efficient digestion of starch-heavy food. The difference in measured starch digestion between the two species is substantial.
Two further genes in the same pathway show similar changes, which points to selection acting on the whole process rather than a single accident.
What the pattern suggests about domestication
The expansion tracks the arrival of agriculture. Dogs living near settled people had access to grain-based waste that wolves did not.
Animals able to extract more from that material would have done better, and the copy number distribution across modern dog populations broadly reflects the agricultural history of the regions they come from.
Breeds developed in places where cereal farming was limited tend to carry fewer copies, which fits the same explanation.
Why this does not settle diet debates
The finding establishes that dogs are equipped to use starch, not that any particular proportion is optimal.
Being able to digest something and thriving on a diet built around it are separate questions, and the second has not been answered by copy number data.
Individual variation also matters. A dog at the low end of the range may handle a high-starch diet less comfortably than the species average would suggest.
Cooking is the other half of the story
Raw starch is poorly digested by dogs regardless of enzyme production, because the granules resist attack until heat and water disrupt their structure.
Extrusion and cooking accomplish that, which is why processed carbohydrate sources are digested far more completely than raw ones.
This is a practical point for home-prepared diets, where undercooked starch passes through largely unused and can produce loose stools without any underlying problem.