Did ‘puppy dog eyes’ expression evolve exclusively in dogs due to domestication?

New research reveals that coyotes, like domestic dogs, have the ability to produce the famous “puppy dog eyes” expression. The study challenges the hypothesis that this facial feature evolved exclusively in dogs as a result of domestication. The researchers examined the levator anguli oculi medialis (LAOM), the muscle responsible for raising the inner eyebrow to create ‘puppy dog eyes’, in coyotes. Contrary to previous assumptions, they discovered that coyotes also possess a well-developed LAOM, similar to dogs. This finding contradicts the idea that the muscle evolved specifically for communication between humans and dogs during domestication.

The researchers compared the facial muscles of coyotes, dogs and gray wolves. While both dogs and coyotes possess a well-developed LAOM, the muscle is either modified or absent in gray wolves. This challenges the hypothesis that human-driven selection was solely responsible for the development of the inner brow raiser in dogs. Instead, the LAOM might have likely been present in a common ancestor of dogs, coyotes and gray wolves but was later lost or reduced in wolves. The LAOM may have originally evolved for functions related to vision and eye movements, rather than communication with humans, as previously thought.