The anatomy of dogs varies tremendously from breed to breed, more than in any other animal species, wild or domesticated. And yet there are basic physical characteristics that are identical among ...

Article #18-20653: "Evolution of facial muscle anatomy in dogs," by Juliane Kaminski, Bridget M. Waller, Rui Diogo, Adam Hartstone-Rose, and Anne M. Burrows.

New research shows domestication has altered dogs' facial structure such that they have a unique muscle allowing them to raise their inner eyebrows, but wolves do not.