Did you know that there are about 900 million dogs in the world today? And the loveable, sometimes strange looking, and usually affectionate weirdos cuddling up to us on our couches make up fewer than 20% of that 900 million! Free roaming dogs, also known as village and feral dogs, make up the rest. But what exactly are dogs, where did they come from and how did they come to live with us.
Biologically, dogs are mammals from the canine family. They are a unique species in many ways; not only are they the only animal that loves us no matter what, they are also the first domesticated animal, and they are also one of only a very few predators to have ever been domesticated. Dogs have an amazing ability to form social bonds with humans. These attachment behaviours are really similar to those of human babies towards their mothers. Dogs seem to intuitively know our emotional states; they exhibit comforting behaviours when we are upset and rejoice when we are happy. Dogs even prefer to spend time in the company of humans more than they do with other dogs. They fit so well into our society that they can socialise with a wide variety of species that are associated with humans, like livestock. These traits allow them to live, for the most part, peacefully with us.
It’s strange to think that whatever breed of dog you have, whether it’s a French bulldog, Great Dane, Collie or Saluki, that they are all the same species and they are all equally related to their closest cousin, the grey wolf. This means that they all share a common ancestor; in other words, they all shared the same great, great x 5000ish grandmother. We don’t know long ago this great grandmother lived but fossils can give us some clues.
The oldest fossil evidence that dogs existed is from 26,000 years ago where footprints of a young boy are accompanied by the paw prints of what appears to be a dog. Usually though, it’s fossil skulls that are the most important when trying to figure out our early history with dogs. When you think about the difference between a chihuahua and a wolf you would think it would be easy to tell a dog from a wolf skull apart. And there are fossils of dogs bred for specific purposes (sledging and hunting) that are from 9,000 years ago. However, the dog skulls that are most important when looking at our early history with them pre-date the existence of the huge variety of breeds that exist today. Going back over 10,000 years ago archaeologists find it difficult to tell whether the skull found is really a dog or a wolf.
Typically, the distinction is made on the basis of the size and proportion of the fossil; if it’s big it’s a wolf and if it’s small it’s a dog. Scientists also compare features of the fossils such as teeth size and crowding, size of the brain case, length and width of the snout, against other known fossils to help make their decision. If that doesn’t sound complicated enough, keep in mind that the fossils that researchers get are often just damaged bits and pieces. Despite this, the oldest known complete skeleton is of a 14,000 year old puppy apparently being embraced by a human which hints that there may have been a close bond existing between them. Although it is possible dog fossils older than that may exist, the nearly complete overlap in measurements in the structure of the bones between dogs and wolves means no one knows for sure.
But fossils aren’t the only historical record we have to look at. Art and literature from the past also give us clues. As far back as the 14,000 years ago there is a story about the Emperor Woo having a dog called Ao. There are also cave paintings that show humans and dogs hunting together from 10,000 years ago and some from 8,000 years ago even seem to show that the dogs also were tethered to humans with leads. However, no artistic depictions of dogs before 14,000 ago have been discovered despite the earliest known cave paintings dating from over 40,000 years ago. Which is weird if humans had dogs as we know them today, surely there would be plenty of cave paintings of them. If my phone is anything typical, I have many, many photos of dogs on there. But cave art depictions of carnivores, including wolves or dogs, and of humans are rare in general. This had led to some experts speculating that the portrayal wolves and humans might have been taboo; like how some Native American tribes don’t like to have their photograph taken in case it steals their soul.
We can also estimate the time dogs and wolves shared a great grandparent genetically as DNA mutates at a predictable rate. By comparing the differences between specific parts of the DNA in 2 species will give a good approximation from the time since they shared a great grandparent. Using this so-called ‘Molecular Clock’ scientists have compared the DNA of modern and historic canid species and concluded that the divergence took place sometime between 10,000 - 40,000 years ago. By comparing the wolf, dog and jackal sequences, it was estimated that dogs and wolves diverged 11-16 thousand years ago. But, when the DNA of modern dogs and wolves were compared to the DNA of an ancient wolf extracted from a 35,000-year-old fossil, models placed the ancient wolf close in time to the split between dog and wolf lineages. This genetic evidence for when dogs first appeared does not yet yield consistent results for many reasons like the assumptions made about the rate of mutation which may not be completely accurate.
So, we don’t know for sure when dogs and wolves shared a great grandmother, but I if I had to make a guess, I’d say about 14,000ish years ago. But I could be convinced it was longer ago than that if more evidence is uncovered or genetic methods are refined.
That’s the when, now onto the why dog’s exist. Dogs exist because of a process called domestication. Domestication produces a species that becomes able to live with humans. It is a process that occurs because of a combination of natural selection and selective breeding. Natural selection acts on the fear response of the population becoming domesticated by reducing it, and by making it less aggressive or even affectionate towards humans. Selective breeding is human controlled and involves selecting individuals to reproduce based on characteristics people what for the next generation. Changes due to domestication can happen really quickly; evolutionary speaking. This was shown by a famous experiment on foxes by a scientist called Belyaev in the 1950’s. Belyaev put a population of foxes through selective breeding with the only criteria being for tameness. That is, every generation he would attempt to approach the foxes with an outstretched hand and those that reacted with less fear and aggression to humans were allowed to breed.
The results appeared much quicker than anyone predicted. By the third generation none of the pups responded with the wild-type behaviour of fear and aggression to humans. By the fourth generation, some of the pups started wagging their tails like dogs. And by the sixth, whimpering, whining, and licking appeared in some of the pups’ behavioural repertoire. And these behaviours became nearly universal in the population by 2005.
Friendliness caused strange things to happen in the wolfish ancestors of dogs too. They started to look different. Domestication gave them splotchy coats, floppy ears, wagging tails. But the changes did not just affect their looks. Changes also happened to their psychology. These early dogs evolved the ability to read human gestures. This ability accounts for the extraordinary communication we have with our dogs. Some dogs are so attuned to their owners that they can read a gesture as subtle as a change in eye direction.
Early humans were not necessarily able to selectively breed for tameness like Belyaev did with the foxes. However, tameness would likely have helped wolves succeed around humans. Potentially, more docile wolves would have more babies, but also any aggressive wolves would probably have been killed because of the danger they would have posed to humans.
But why did dogs become domesticated? To answer this question a good clue is to look at where dogs originated from. And parallel to the question of where dogs may have been domesticated is the issue of whether domestication happened only one time in one place or many times in many places. If dogs were domesticated once, then that suggests that something was special about the place and time that domestication happened. If it was more than once in more than one place, then it would be interesting to know what these places had in common that might help explain the conditions needed for domestication to happen.
The oldest accepted dog fossils are found in the Middle East, across Europe, and northern Eurasia. This suggests that one, or a few, of these sites are where domestication happened. But the difficulties remain in telling apart fossils of dogs from wolves. Some recent genetic and archaeological evidence are converging on Eurasia as the likely region for dog domestication. More specifically, it suggests that dogs were domesticated in Siberia about 23,000 years ago when both species lives as nomads. However other genetic evidence points to southern China as where dogs originated from.
As the greatest genetic diversity found in a population is normally where the species originated, genetically testing dogs can yield insights into their history. This is because when new populations are formed, they have only a selection of the genetics from the original founding population. And it’s been found that village dogs have the greatest genetic diversity of all dogs.
There are many dogs that exist today as village dogs. They are presumed to live much as dogs did earlier on in their domestication. Balinese village dogs live off human dumps and African village dogs as known to follow children waiting for them to go to the toilet. As disgusting as that sounds, disposing of waste in this way benefits human society by reducing rat populations and the diseases they carry. So, people that allow dogs to follow them and clean up their waste in areas with no sanitation are more likely to be survive.
This gives us a reason for dog domestication occurring which has been proposed to be during the Neolithic when humans first started farming. The idea is that the ancestors of dogs began to scavenge near human settlements. Dogs may have originated from the novel environmental niche that human leftovers would have created after humans adopted a more sedentary farming lifestyle. And domestication is strongly associated with these settlements, which in turn are tied to the advent of agriculture that took place about 10,000 years ago. Once dogs were domesticated, they accompanied their human companions all over the globe. For example, Middle Eastern families expanded into Europe 10,000 years ago and, based on genetic evidence, it looks like they took their dogs with them.
But you might remember that some of the estimates for dog domestication are a lot older than 10,000 years which would mean that dog domestication began when human still lived as wandering hunter gatherers. So, how could this have occurred in a niche that didn’t exist yet?
An alternative story is that, as both wolves and humans have similar social structures and hunt similar prey, they may have learned to use each other to mutual benefit. Wolves, back in the days of human hunter gatherers, would have likely been much bolder around humans than wolves that exist today, like how urban foxes are now pretty bold and easily seen in cities todays. Humans and the first domestic dogs may have evolved together as hunter gatherers before humans settled down in the one place to grow crops. And people who had dogs during a hunt would likely have had an advantage over those who didn't. Even today, tribes in Nicaragua depend on dogs to detect prey, moose hunters in alpine regions bring home 56% more prey when they are accompanied by dogs and hunters believe they would starve without their dogs there to help them in the Congo.
The evolutionary history of a species sets the limits of what is possible in the behaviour and physiology of the species. When behaviours exist in dogs that also exist in other canid species, it gives insights into what dogs are capable of, and what they have strong impulses and desires for. Like the play bow that signifies friendly intentions or the snarl for unfriendly ones. Knowing this also allows us to be better at interpreting their doggie language.
Apart from the history of dog domestication being an interesting tale to tell, what is the point in trying to understand where our dogs came from? Well, I think the more that is known about dog ancestry, the more that can be done to make the environment, welfare and training of dogs as good as we possibly can.