image: Facial musculature in the dog (left) and wolf (right) with anatomical differences highlighted in red. view more
Credit: Image courtesy of Tim Smith (artist).
A study suggests that expressive eyebrows in dogs may be a result of human preferences that influenced evolutionary selection. The anatomy and behavior of dogs, which were domesticated more than 33,000 years ago, have evolved to enable communication with humans. Dogs can raise their inner eyebrows, making their eyes appear larger and infant-like and producing a movement similar to one made by humans when they are sad. To determine whether this eyebrow movement is a result of evolution, Juliane Kaminski and colleagues compared the facial anatomy and behavior of dogs and gray wolves; 4 wild wolves and 6 domestic dogs were used for the comparative facial anatomy analysis, and 9 wolves and 27 shelter dogs were used for the behavioral analysis. The muscle that raises the eyebrow was present in dogs but represented by scant fibers in wolves. Unlike gray wolves, almost all dogs studied possessed the muscle that pulls the lateral corner of the eyelids toward the ears. The only dog species without the muscle was the Siberian husky, which is among ancient dog breeds. When exposed to a human for 2 minutes, dogs more frequently raised their inner eyebrows and at higher intensities than wolves; dogs, but not wolves, produced the highest intensity movement. The findings suggest that dogs may have evolved expressive eyebrows as a result of human preferences.
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.
MEDIA CONTACT: Juliane Kaminski, University of Portsmouth, UNITED KINGDOM; tel: +44-2392846301, +44-7539344686; email: juliane.kaminski@port.ac.uk; Kate Daniell, University of Portsmouth, UNITED KINGDOM; tel: +44-2392843743
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