Dog and Wolf Eye Muscle Comparison

Here's a fascinating science discovery about humanity's oldest companion. Dogs have been found to have two extra eye muscles that their ancestors, gray wolves, don't have. These eye muscles allow them to shape their eyes into the well-known sad puppy dog stare when desiring human attention. The muscles allow dogs to widen their eyes and raise their inner eyebrow area. These muscles appear to exist for the sole purpose of generating human connection. It makes them appear more like human babies in their facial appearance and people usually describe the look as meaning that the dog must be sad. The dogs use them when they desire human eye contact. Dogs will turn to humans and make eye contact when they are faced with a problem they can't solve. Wolves will not. Dogs closest to their wolf ancestors in form, like Siberian Huskies, only have one of the muscles developed. Wolves do have some sparse muscle fibers, that have not developed into full blown muscles, where dogs have these muscles. So wolves can not generate the full expression, even if they wanted to. Scientists believe these dog muscles evolved through selection pressures unwittingly exerted by humans. Dogs that could appear the most expressive facially were selected for preferential treatment by humans, which meant that overall these dogs were cared for better and thus had better chances at healthy offspring. There are only two other animal groups that have these muscles besides dogs and humans: apes and horses. In horses, however, the muscles do not achieve the same look that they do in the other three animal groups due to horse facial structure.

Link: Procedings of the National Academy of Sciences of the United States of America