New research suggests that ancient humans played a role in selecting dogs with sweetest faces.
Humans domesticated dogs (Canis familiaris) with attention to the facial expressions that dogs produce, selecting for a suite of facial movement.
Domestic dogs and humans are adept at accurately understanding one another’s facial expressions and movement around the eyes in dogs is highly valued by humans.
This unique, mutual ability to accurately process facial expressions is part of the dog-human bond.
An accurate understanding of how faces of dogs and gray wolves (Canis lupus) differ from one another is fundamental to understanding the processes of animal domestication, evolution of the dog, and the origins of human behavior since the Upper Paleolithic period.
“Dogs are unique from other mammals in their reciprocated bond with humans which can be demonstrated though mutual gaze, something we do not observe between humans and other domesticated mammals such as horses or cats,” said Duquesne University’s Professor Anne Burrows.
“Our preliminary findings provide a deeper understanding of the role facial expressions play in dog-human interactions and communication.”
In the new research, Professor Burrows and her colleague, Kailey Omstead, focused on the anatomy of tiny muscles used to form facial expressions, called mimetic muscles.
In humans, these muscles are dominated by fast-twitch myosin fibers that contract quickly but also fatigue quickly, which explains why we can form facial expressions rapidly but not hold them for long.
Muscle cells with more slow-twitch fibers are more efficient for long, controlled movements and don’t tire as quickly.
For the study, the authors compared the myosin fibers in facial muscle samples from wolves and domesticated dogs.
Their results revealed that, like humans, both dogs and wolves have facial muscles that are dominated by fast-twitch fibers, but wolves have a higher percentage of slow-twitch fibers relative to dogs.
“These differences suggest that having faster muscle fibers contributes to a dog’s ability to communicate effectively with people,” Professor Burrows said.
“Throughout the domestication process, humans may have bred dogs selectively based on facial expressions that were similar to their own, and over time dog muscles could have evolved to become faster, further benefiting communication between dogs and humans.”
Having more fast-twitch fibers allows greater facial mobility and faster muscle movement, enabling small movements such as a raised eyebrow and the short, powerful muscle contractions involved in barking.
Slow-twitch fibers, on the other hand, are important for extended muscle movements such as those wolves use when howling.
“Further research is needed to confirm our new findings with antibody stains suitable for differentiating additional myosin fiber types, which could shed new light on the anatomical differences between dogs and wolves,” the scientists said.
They presented the findings today at the American Association for Anatomy annual meeting during the Experimental Biology (EB) 2022 meeting in Philadelphia, the United States.
Anne Burrows & Kailey Omstead. Dog Faces Are Faster than Wolf Faces. EB 2022, abstract # 408.4
Source link: https://www.sci.news/biology/dog-faces-10686.html