Dogs came from wolves, a very long time ago. They belong to a family of animals called canids, along with wolves, coyotes, foxes and jackals. Dogs have lived with people for at least 14,000 years. 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. 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. 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.
Belyaev proposed that calmer wolves hung around people because scraps gave them steady food, and that as these calmer wolves interbred they became less afraid of people. It is an idea, not settled fact. 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. A later, larger study found that some wolves also carry extra AMY2B copies, and that dingoes have two copies and Siberian huskies only three or four. A population geneticist said the later data make a case against starch digestion playing a key role in taming dogs.
The 2013 study found that the wolves it compared were all equally related to dogs, so none could be called the dog ancestor. The authors suggested an unknown, possibly extinct, wolf was the source. That study dated dog domestication to about 15,000 years ago, well before farming began. Interbreeding between dogs and wolves after domestication made some wolves look more closely related to dogs than they really are, which blurs the search for where dogs began. A 2020 study sequenced 72 ancient wolf genomes from Europe, Siberia and North America spanning the last 100,000 years. Where dogs first appeared is hard to say: it could have been in the Middle East, China, Siberia or several places at once.
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 experiment began hidden inside a larger program to breed better foxes for the fur industry. The idea Belyaev and Trut 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. 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. The results supported Trut and Belyaev's ideas and changed how scientists understand domestication.
In 2015 a study found that when a dog gazes at its owner, the owner's oxytocin level rises, which prompts more social contact. In the study, 30 dog owners spent half an hour with their dogs, and owners whose dogs gazed at them longest had the biggest rises in oxytocin. Owners who got more gazes looked back, touched and talked to their dogs more, and dogs that got the most attention in return also had the biggest oxytocin spikes, so each raised the other's oxytocin in a loop. 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.
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. A researcher suggested that dog evolution probably selected for eye-gazing, a behavior that gives people a body response that helps them bond. Brain scans show that some of the same brain regions become active when human mothers look at pictures of their children or their dogs. Other scientists said it was too early to say the gaze loop evolved with domestication, because the same loop might also form between puppies and any caregiver, including a dog mother. 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 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. The study's authors said the results support the idea that domesticating dogs from wolves changed the way dogs think. A different set of experiments tested whether dogs use a person's body orientation, which shows what the person can see, when following a point. Dogs tended to follow the gesture from the person who faced them.
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. If a dog you do not know comes up to you, stay still and quiet instead of running.
Brachycephalic dogs are flat-faced breeds with shorter skulls, like pugs and bulldogs. People bred them to have these features and found the look attractive. BOAS, short for brachycephalic obstructive airway syndrome, is a chronic disease of short-skulled dogs in which 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, and 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. Risk of BOAS varied a lot by breed, and boxers and Staffordshire bull terriers rarely had breathing issues. The researchers found dogs with wider, shorter head shapes were more likely to have BOAS.
A study author said the link between muzzle length and BOAS risk is more complex than commonly assumed. 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. The most severely affected flat-faced dogs struggle constantly to get air, but many owners think this is normal for the breed and do not seek treatment. A veterinary professor argues that breeders and vets should be trained to grade the fitness of dogs before breeding to avoid producing offspring with the worst problems. Dogs' flat faces, like pugs and bulldogs have, can make it hard for them to breathe.
Words to know
- genomes: full gene sets
- oxytocin: bonding chemical
- dingoes: wild Australian dogs
- generations: family steps
- selective: chosen on purpose
