Dogs really do love their human owners, according to a Tuesday presentation at BAR by Science Diplomats — a consortium of Yale graduate students who aim to bring scientific topics to the public.
Erin Heim GRD ’18 and Zuri Sullivan GRD ’20, the organization’s co-presidents, joined Angie Johnston GRD ’18 and Molly Crossman GRD ’19 to discuss the special relationship between dogs and humans using genetic, microbial and psychological research. Sullivan launched the series of informal talks this year to engage greater New Haven residents in science relevant to daily life. More than 100 community members turned out on Tuesday to learn about dog domestication and more, while enjoying pizza and specialty drinks such as the “Whiskey Schnauzer” and “Muttini.”
“One thing that we know is that dogs show the same behavioral evidence of being attached to their owners as children do to their parents,” Johnston said. “They are more excited to see their owner when reunited after a long period of time than they would be a stranger.”
Johnston, whose research in the Psychology Department focuses on human and animal recognition of others, said the neurochemicals involved in interactions between a dog and its owner are very similar to those released when infants encounter their parents. When they look at each other, dogs and humans release oxytocin — a hormone typically emitted in mammals when bonding, especially with their mates. So far, Johnston added, scientists have yet to discover another instance of an inter-species release of oxytocin, further bolstering the evidence dogs have a unique connection with humans.
While other animals may make eye contact with humans, Johnston said, dogs tend to do so for longer spans of time and without aggression.
Dogs’ oxytocin release seems to be a product of domestication, an evolutionary process Heim traced back to wolves in the hunter-gatherer era. Heim said DNA evidence suggests that dog domestication, a passive, slow process of genetic modification, may have occurred any time from 10,000 to 1 million years ago. But dogs’ relationship with humans began around 14,000 years ago — when evidence suggests dogs and humans started being buried together.
Heim said it is likely that wolves underwent passive domestication, in which they realized they would have access to more food by being friendly to primitive humans who left behind remnants from the animals they hunted. These wolves, now better fed, left more offspring, which over time became friendlier and friendlier to humans. Due to the phenomenon of linked genes — which are passed down in tandem from parent to offspring due to proximity on chromosomes — traits such as white spots, floppy ears and an under-bite accumulated in domesticated dogs.
Sullivan said dogs’ connection to their owners actually has a microbial basis. She said families that live together share parts of their microbiome, which consists of trillions of bacteria that live mainly in the intestine and assist with digestion and other processes. Since mammals have a skin microbiome in addition to the microbiome found in the gut, Sullivan said, humans often pass and share bacteria with their dogs due to close proximity and frequent touching.
Crossman closed Tuesday’s presentation by discussing the benefits of therapy dogs, which are used to improve humans’ mental health. Crossman said dogs boost positive emotions and reduce stress by providing social support to humans.
“I think we all really love our dogs, and when we start to talk about what the benefits are, most people have something to say just from their personal experience,” Crossman said.
The American Kennel Club currently recognizes 167 breeds of dogs.