A recent study disputes the theory that ‘puppy dog eyes’ developed solely in dogs due to domestication.
Research conducted at Baylor University indicates that coyotes can also exhibit the well-known “puppy dog eyes” expression. The study, titled “Coyotes can do ‘puppy dog eyes’ too: Comparing interspecific variation in Canis facial expression muscles,” appeared in the Royal Society Open Science, and counters the notion that this facial expression evolved only in dogs as a result of their domestication.
The team, led by Patrick Cunningham, a doctoral student in biology at Baylor University, investigated the levator anguli oculi medialis (LAOM), the muscle that raises the inner eyebrow to create the “puppy dog eyes” look, in coyotes.
Contrary to earlier beliefs, Cunningham and his colleagues found that coyotes possess a well-developed LAOM, akin to that of dogs. This discovery challenges the idea that this muscle evolved exclusively for communication between humans and dogs during the domestication process.
“Our results indicate that the ability to show ‘puppy dog eyes’ is not a feature unique to domesticated dogs but rather an inherited trait shared by various species within the Canis genus,” Cunningham remarked. “This opens up intriguing questions regarding the significance of facial expressions for communication and survival among wild canids.”
Comparisons between Coyotes, Dogs, and Gray Wolves
Cunningham and his team assessed the facial muscles of coyotes, domestic dogs, and gray wolves. Both dogs and coyotes have a well-formed LAOM, while this muscle is either altered or missing in gray wolves. This undermines the hypothesis that human-driven selection was entirely responsible for the development of the brow-raising muscle in dogs. Instead, the findings imply that the LAOM was likely present in a shared ancestor of dogs, coyotes, and gray wolves, but became diminished or lost in wolves over time.
The study also noted considerable variation within the facial muscles of coyotes, specifically those involved in raising brows and manipulating lips. Genetic analysis confirmed the lack of significant dog ancestry in the coyote specimens, further emphasizing that these characteristics are not due to interbreeding.
“Our research highlights that coyotes and dogs share not only behavioral traits but also an intriguing evolutionary background that includes facial expressions previously thought to be exclusive to domesticated animals,” Cunningham stated.
This finding has considerable implications for our understanding of the evolution of facial expressions in mammals. The LAOM might have initially evolved for purposes related to visual function and eye movement rather than for human communication, as was previously believed. Further studies on different canid species, such as red wolves and African wild dogs, could shed more light on how facial expressions contribute to survival and species communication.
This study received support through a grant from the National Institute of Food and Agriculture, U.S. Department of Agriculture McIntire-Stennis Program, under award number 1027755 and Michigan Technological University REF R01787.
