People still argue about when, where and how dogs were domesticated. Scientists have worked out the time, place and ancestry of nearly every other domesticated animal, from sheep to chickens, but not dogs. The scientist Dmitri Belyaev proposed that calmer wolves hung around people because scraps gave them steady food. He also proposed that as these calmer wolves interbred they became less afraid of people. It is an idea, not settled fact. The older idea that Stone Age people risked their lives to steal wolf cubs as guards, workers or companions makes less sense, Belyaev and his colleague Lyudmila Trut argued, than the idea that calm wolves came to people.
Dmitri Belyaev asked Lyudmila Trut to lead an experiment with foxes, which are closely related to dogs, to see how domestication unfolded and which evolutionary forces were at work. The idea they tested was that domestication syndrome, which means floppy ears, curly tails, youthful faces and mottled fur, came from always breeding the calmest, friendliest animals in the early stages of domestication. Trut tested each fox by seeing how it reacted when she approached its cage, opened the door and put in her gloved hand. Many of the tame foxes kept childlike traits into adulthood, like floppy ears, curly tails and baby faces, that their wild cousins outgrew. After about 15 generations of selective breeding, the experiment had foxes that could live with people.
In 2013 a study of 60 dogs from 14 breeds and 12 wolves found that dogs have more copies of AMY2B, a gene for an enzyme that breaks starch into sugars, than wolves do. The researchers on that 2013 study said both brain changes and diet changes were probably needed for wolves to become dogs. Most genetic evidence says dogs emerged in the farming era, but some dog fossils are much older, dating as far back as about 33,000 years ago. Some archaeologists say there were domestic dogs by at least 15,000 years ago. How much earlier is argued, with some saying 30,000 years. Where dogs first appeared is hard to say. It could have been in the Middle East, China, Siberia or several places at once.
In 2015 a study found that when a dog gazes at its owner, the owner's oxytocin level rises, which prompts more social contact. Owners who got more gazes looked back, touched and talked to their dogs more. Dogs that got the most attention in return also had the biggest oxytocin spikes. So each raised the other's oxytocin in a loop. When 27 dogs got oxytocin by injection, the female dogs gazed at their owners more, and the owners' oxytocin rose. It is not clear why only the females did. Eleven pure-bred wolves raised by people did not make regular eye contact with their owners, and their gaze did not raise the owners' oxytocin. Among wolves, eye contact is a threat, so wolves rarely look directly at each other.
A Duke study of 44 dog puppies and 37 wolf puppies, 5 to 18 weeks old, tested how well puppies read human gestures. The dog puppies followed a person's pointing at hidden food without training, but the wolf puppies did no better than chance. The wolf puppies had near-constant human contact from just after birth, and were hand-fed, so the difference was not due to a lack of time with people. Chaser the border collie was trained by retired psychology professor John Pilley starting in 2004. He showed her 1,022 objects in total. Chaser was tested for three years. In 838 tests she never scored below 90 percent, according to the researchers' report. Dogs follow a person's pointing finger to find hidden food, even puppies that were never trained to.
About 12 percent of the air a dog breathes in detours into a recessed area at the back of the nose that is only for smelling. The rest goes to the lungs. A dog's nostrils each reach only a small area. This helps it tell which nostril a smell came in through, and so work out where the smell is coming from. In a study in Norway, a hunting dog with its head high into the wind sniffed in a continuous stream of air for up to 40 seconds, across at least 30 breaths. In one study, dogs led at right angles to a trail that a person had just walked could tell which direction the person went. They could do it from as few as five steps.
One study showed dogs videos of other dogs wagging their tails. Dogs that watched a dog wag to the left had faster heart rates and looked anxious, but those that watched a dog wag to the right stayed relaxed. The same research team had found that dogs wag to the right when they feel positive emotions and to the left when they feel negative ones. The researchers do not think the dogs are necessarily meaning to tell other dogs. A wagging tail or a crouching body does not always mean a dog is friendly. Before you pet a dog, ask its owner if it is okay. If a grown-up says you can, let the dog sniff your closed hand first.
BOAS, short for brachycephalic obstructive airway syndrome, is a chronic disease of short-skulled dogs. In it, narrowed airways cause noisy breathing and can limit exercise, sleep and coping with heat. From 2021 to 2024 a team in England studied nearly 900 dogs of 14 short-skulled breeds. They found 12 of the 14 breeds had some breathing abnormality. In the study, 89 percent of Pekingese and 82 percent of Japanese Chin were affected by BOAS, rates like those of pugs, French bulldogs and bulldogs. From 2006 to 2016 the number of registered bulldogs in the U.S. went up by 60 percent and French bulldogs by 476 percent. In 2023 the French bulldog topped the American Kennel Club's list of most popular breeds.
Dogs have lived with people for at least 14,000 years. A new analysis of the bones and teeth in a grave at Bonn-Oberkassel found two dogs, an older dog and a younger one, where researchers had thought there was one. Other ancient dog burials date to about 11,600 years ago in the Near East, about 8,500 to 6,500 years ago in Scandinavia and about 8,000 years ago in Illinois. One article says dogs worked for people as shepherds, guard dogs and hunters from the beginning of their domestication, and calls the pet-and-family bond a relatively recent thing.
A 2018 study found that the younger Bonn-Oberkassel puppy probably caught canine distemper at about 19 weeks old and had two or three periods of serious illness lasting five to six weeks. The puppy probably could only have survived thanks to long and intensive human care, the study's authors said, because distemper is a life-threatening sickness. A study author said the puppy was too sick to be a working animal, which suggests people cared for it for something other than its use. A museum curator on the study said that at least some Paleolithic people saw dogs not just as useful but already had a strong emotional bond with them.
Words to know
- domestication: taming over time
- oxytocin: bonding chemical
- distemper: a dog sickness
- syndrome: set of traits
- Paleolithic: Stone Age
