It’s no accident that dogs have sad-looking eyes.
A study published last year suggested that a facial muscle called the levator anguli oculi medialis evolved in dogs specifically to allow them to raise their eyebrows in a way that humans find adorable. Babies do it, too. Wolves, on the other hand, have no particular reason to get humans to do their bidding, preferring to eat us rather than trick us into buying dog food.
Dogs were domesticated only about 33,000 years ago — a veritable eye blink in terms of evolutionary time scales.
Dogs wasted little time getting their faces set up in a way that cemented their place in human society. Any dog that couldn’t get the right kind of response out of humans wouldn’t stick around long, suggesting that “dogs’ expressive eyebrows are the result of selection based on humans’ preferences,” according to the study, first published in June 2019 in the Proceedings of the National Academy of Sciences by British canine researcher Juliane Kaminski and colleagues.
How this works seems
a little bit creepy.
When mothers and babies gaze into one another’s eyes, it triggers a flood of oxytocin, a hormone that creates contractions during labor and stimulates lactation. It also helps with maternal bonding. Men have it, too. Turns out oxytocin does some things in the brain as well, serving as a chemical messenger of warm and fuzzy feelings. It’s known in some circles as the “love hormone.”
That same kind of hormonal flow happens when humans and dogs look at each other. Kaminski’s study thus offers evidence that dogs, probably some time way back in cave-dwelling days, “hijacked the human caregiving response.”
We find babies and puppies “cute” partly because their eyes look so big. Adult humans and dogs with infant-like features also tend to float our boats. Don’t ask me why. In any case, this raised eyebrow thing seems to make one’s eyes look even bigger, which studies have shown seems to be particularly attractive to humans.
Doggies with a more pronounced tendency to jack their eyes up get placed quicker from shelters. Wolves, by contrast, seem to narrow their eyes into cat-like slits, which makes them look mean and venomous. Nobody wants to take one of them home.
Given how well this copying of the human nurturing equipment and emotional trickery have worked for domestic canines, you might wonder what other changes might be happening as the evolutionary advantages of human interaction works through what’s left of the animal kingdom.
It’s probably too little too late for rhinos and lions, given extinctions rates. But I’d wager that even cats, given 10,000 or so more years of evolution, might someday figure out a way to look cute and cuddly.
Carl T. Hall is a longtime union organizer in San Francisco who is now a co-owner of Word. A Café, now open for business in the Bayview Neighborhood. Readers can pick up copies of Bay Woof there, too.
Main article photo by: Graphic from the Proceedings of the National Academy of Sciences, July 16, 2019