Puppy-dog eyes didn’t just evolve to influence humans, study finds

Large and droopy “puppy-dog eyes” did not just evolve in domesticated dogs to appeal to humans, as scientists had previously thought, according to a new study that sheds more light on canine evolution.

Previous research papers published in 2019 and in 2022 theorised that dogs evolved new muscles around their eyes specifically because this facilitated more effective communication with humans.

But a new study of African wild dogs debunks this theory, finding that other canine species have similar muscle adaptations that allow them to pull sad-looking expressions.

Previous research compared the facial muscles of dogs with those of wolves to find that the pooches developed specialised muscles around their eyes to make a wider range of facial expressions. Scientists theorised these muscles evolved because they allowed domesticated dogs to mimic human facial expressions and thereby encourage their companions to take better care of them.

The latest research, published in the journal The Anatomical Record, scientists dissected a dead African wild dog (Lycaon pictus) specimen donated by a zoo and found that these canines also have the same “puppy-dog eye” muscles.

Not only were these facial muscles present in the wild dogs, but they were also shown to be just as developed as those seen in their domesticated cousins. In addition, some facial muscles in the African wild dog appear to support fine manipulation of its characteristically large, mobile ears.

“This morphology suggests that ocular facial expressions contribute to within-pack communication in wild dogs and are not unique to domestic dogs,” researchers wrote in the study.

“African wild dogs have the same well-developed facial muscles that generate the “puppy dog eye” expression in domestic dogs!,” said study lead author Heather Smith from Midwestern University in the US.

While African wild dogs are known to communicate mostly vocally, their well-developed muscles of facial expression hints the canines may also have other yet unknown non-vocal forms of communication within packs, researchers say.

They speculate that non-vocal communication may be particularly useful for the animals, highly social canines that hunt across the plains of Africa in packs of five to nine individuals, to communicate silently across their grassy habitat.