Dogs are the animals most loved by humans. Frederick the Great of Prussia (1742-1786) was reputedly the first person to call dogs "man's best friend", referring to his Italian greyhound. The biological underpinnings of the unique bonds that form between humans and dogs are described in a fascinating article recently in the Bulletin of the American Council on Science and Health by Chuck Dinerstein.
Dogs are part of a large taxonomic family called Canids that also includes wolves, coyotes, foxes and jackals. The dog (Canis lupus familiarus) is descended from the wolf (Canis lupus). The domestication of animals began with grey wolves as long as 30,000 years ago when humans were still nomadic. Dogs and wolves diverged genetically since that time and modern wolves are not closely related to the population of wolves first domesticated.
Dogs and wolves are carnivores and, in the wild, must hunt and kill their prey in order to eat. However, as Dinerstein explains, unlike tigers and other larger carnivores, lone wolves (or dogs) are mostly unable to kill prey on their own, and so they travel and attack in packs. Of course, domesticated dogs no longer have to hunt prey in packs, but they remain pack animals by instinct.
Dogs and wolves are social creatures, but dogs are also naturally cooperative with humans. There is evidence that dogs, but not wolves, are genetically programmed with an exaggerated motivation to seek out and maintain social contact with humans. Wolves and other wild cousins of the dog are cooperative with each other but not with humans, which undoubtedly makes them less attractive than dogs to us humans.
Bond so well
Why do humans and dogs bond so well? Human infants learn to look in the same direction as the parent is looking and this “gaze direction” is a non-verbal means of communication. Dogs also have this ability and to a much greater extent than wolves. And dogs are much more motivated than wolves to establish eye contact with humans. This mutual eye-gazing between human and dog is reinforced and enhanced by release of the hormone oxytocin, just as happens between a human mother and her baby.
As Dinerstein explains, we humans are naturally attracted to our own young and we also like animal faces that remind us of infants (pedomorphism). Dogs are particularly adept at presenting infant-like facial expression because they have the facial muscles to raise the inner and upper aspects of their eyebrows to produce that well-known soulful look. Wolves are significantly less able than dogs to create this particular soulful look. When a dog with this soulful expression gazes into your eyes, he/she captures your heart.
There are about 987 million dogs in the world but only 20 per cent of these fit the category of “man’s best friend” and they live in the developed world. Dogs in the developing world are more commonly feral or community-owned, with pet dogs uncommon.
It is common for people to forge intense emotional bonds with their pet dogs. This can cause considerable grief when the dog dies. Our 12-year-old Bichon Frise dog, Milo, died in 2017 and we were completely unprepared for the grief we experienced when he went. I described this in my column of July 20th, 2017. I never had a bigger reaction to any other column.
Early humans domesticated dogs because dogs were so useful. Dogs helped humans to hunt and alerted the camp to danger, using their keen senses of hearing and smell. Dogs provided a campsite sanitary service by cleaning up food scraps and even provided warmth to humans on bitterly cold nights. Australian Aborigines have a phrase to describe a particularly cold tonight – “a three-dog night” – a night so cold you need to take three dogs to bed with you to stay warm!
There was widespread public revulsion recently at the shameful news that, of the 16,000 greyhounds born in Ireland in 2017, almost 6,000 were killed because they couldn't run fast enough. Dogs give us great pleasure and companionship, they give us the precious gift of unconditional love and they teach us to appreciate non-human animal life. They should be treasured.
William Reville is an emeritus professor of biochemistry at UCC
