Truth is, their bodies just aren't made for carbs. They don't naturally produce much amylase, the enzyme that's needed to digest carbs. But a funny thing happens after eating carbs...They begin to produce amylase in their saliva within a week! Of course, pet food makers applaud this as a good thing.

Humans first domesticated dogs at least 10,000 years ago, so they went through the agricultural revolution alongside us (2, 3). In other words, when we ate grains and legumes, they ate grains and legumes, at least to some extent. I've described in previous posts how humans acquired genetic adaptations to recent dietary changes (4, 5).

It is therefore fitting that the Nature article is titled "The Genomic Signature of Dog Domestication Reveals Adaptation to a Starch-rich Diet". Along with a variety of genetic changes that may impact brain development and function, they identified changes in three genes that play a key role in starch digestion and absorption. One of these genes, AMY2B, encodes pancreatic amylase, an enzyme that digests starch into glucose in the small intestine. Wolves only have two copies of AMY2B (one on each copy of chromosome 6), while domestic dogs carry 4-30 copies, suggesting that domestication has improved dogs' ability to digest starch.

This is fascinating because a similar genetic change occurred in humans. Dogs only produce amylase in the pancreas, while primates such as humans express it in the saliva in addition to the pancreas. Salivary amylase is encoded by the AMY1 gene. Chimpanzees, which eat a low-starch diet*, only have two copies of AMY1, while humans carry 2-15 copies (average ~6) (6). In other words, both humans and dogs responded to increased starch consumption with similar genetic adaptions. This is an example of a phenomenon called "convergent evolution".