How Dogs (Eventually) Became Our Best Friends

It was the summer of 2018 in Siberia, and a patch of permafrost near the Indigirka River had melted enough to uncover the body of a two-month-old cub. After its almost perfectly preserved remains were discovered, scientists determined that the cub was an astonishing 18,000 years old. The frozen animal was nicknamed "Dogor", not only because of the word "friend" in the local language, but also because of a clever play on words: is it a dog or...? Anything else? And, despite his age, he still had most of his fur, teeth, and even a cute little nose. But while Dogor was in very good condition for a nearly 20,000-year-old puppy, scientists were unable to confirm which species he belonged to.

Was it a dog or was it a wolf? Or was it something in between? Dogor comes from the period when scientists believe wolves were being domesticated, so knowing whether it was a wolf or a dog could help us better understand the specific time, and perhaps even place, that domestication occurred. Because there's still a lot we don't know about how wolves went from fairy tale villains to our canine companions. When were they first domesticated? Where did this happen? And what was the process like, in terms of genetics and anatomy? We're still figuring out the details, but most scientists agree that it took thousands of years of interactions to develop our deep bond with these good boys and girls.

Modern

dogs

….like my good friend Abby…. They belong to the subspecies known as Canis lupus familiaris and their origins date back to a now extinct species of Pleistocene wolf, an ancestor they share with the modern gray wolf, called Canis lupus. But the exact species of this ancestor is still unknown. While some possible ancestral species of wolf have been identified, such as the extinct species from which the Taimyr wolf comes, a specimen discovered in northern Siberia, genetic analysis has shown that they are not direct ancestors of what would become Canis. lupus familiaris. What we can say from studies of dog and wolf genomes is that wolves and

dogs

began to diverge genetically from each other sometime between 40,000 and 27,000 years ago.

And determining the exact moment is difficult, because it seems that the split occurred in a very short period of time, and there was probably interbreeding between domestic dogs and wild wolves along human migratory routes. So dogs still looked a lot like wolves at the beginning of domestication. It's also complicated because the genetic divergence of these two species is not necessarily the same as domestication; one is just a division in the gene pool, while the other is the entire genetic and behavioral process that humans were involved in. But one of the key genetic traits that wolves and modern dogs share, which has been strongly selected for in modern dogs, appears to be hypersociality, which is the tendency of adult animals to initiate social contact even with members of other species.

And for some wolves, this tendency, along with other behaviors, such as scavenging for food, could have made them more suitable for eventual domestication. These traits would also have been useful as human settlements

became

more widespread, with resources that these canines would definitely have desired. This is known as the commensal path to domestication, where an animal benefits from a relationship with humans, but there is little to no benefit to the humans themselves... well, you know, at least at first. In this case, proto-dogs were attracted to discarded human food, which likely also attracted other animals that they could have also preyed on.

And there seems to be some evidence that this probably happened about 28,500 years ago. A new paper published in 2020 was able to distinguish between two different types of canids from a site in the Czech Republic based on the microscopic wear of their teeth. One group had clothes that were better suited to a more meaty diet, while the other group had clothes that suggested they had been chewing on harder, more brittle foods, like bones. And researchers believe the difference means that the bone-chewing group hung around this human settlement more and ate its leftovers. Over time, humans realized that wolves, once domesticated, could be useful: they could be guards, work with hunters, and even help domesticate other species of livestock.

And after that, wherever the humans went, their canine companions followed. In fact, we can trace the expansion of agriculture through a particular genetic adaptation in dogs! In 2013, scientists were able to isolate the gene associated with the shift from the carnivorous diet of wolves to a more starchy diet in dogs. Domestic dogs have more copies of the gene known as AMY2B than wolves. AMY2B encodes an enzyme secreted by the pancreas that breaks down starch. An increase in starch consumption among people is often associated with agriculture, such as growing wheat and rice. And domesticated dogs living in human settlements would also have been fed the kinds of things people ate.

In addition to the difficulties in determining when dogs were domesticated, there has also been some debate about whether it occurred once or more than once. Like cats, dogs were once thought to have been domesticated twice, because in 2016 researchers showed that genetic divergence between European and Asian dogs appeared to occur after dogs were found in these areas, suggesting that domestication occurred in both Europe and Asia. However, another 2017 study suggests that dogs may have only been domesticated once. This research on the genomes of two very ancient dog specimens from Germany shows that this could have happened between 20,000 and 40,000 years ago!

One set of dog remains was 7,200 years old and the other 4,700 years old. And by comparing them to modern wolves and dogs, scientists were able to discover that both had 70 to 80 percent European ancestry in their genetic makeup. And this study found a much older date for genetic divergence between European and Asian dogs than the 2016 study, old enough to suggest that domestication occurred only once. So it appears that there was a continuous lineage of domesticated dogs, rather than two separate domestication events. While we're still figuring out when all of this happened and how it happened, it wasn't long before people

became

deeply attached to their puppies.

And we can see this link in the archaeological record with the burials. In Europe, Asia, Africa and North America, dog burials can be found from the Late Pleistocene to the Middle Holocene. What makes these dog burials special is that many of them were treated and laid down very similar to how humans are buried. This implies that these dogs were seen as very close companions, even in death. For example, archaeologists recovered the remains of a male dog in a roughly 9,000-year-old cemetery in Siberia along with other artifacts, such as a spoon made from a large antler. This dog was an older adult, with evidence of wounds that were partially healed at the time of his death, demonstrating that he had been cared for during his lifetime.

An analysis of the chemistry of one of his vertebrae showed that his diet included both terrestrial and aquatic resources, similar to the diet of people at the site. This could mean that these dogs and humans lived close together, even sharing food. We also see mixed burials in some cultures, where both dogs and humans are laid to rest together. In fact, the oldest known burial of a dog (a puppy that was buried about 16,000 years ago in Germany) was found next to two human bodies. Dogs were also buried alongside their humans in Egypt, where they were often used for hunting and guarding.

This may have been the case with a mummified dog found in a tomb in the Valley of the Kings, which may have been the favorite hunting dog of one of the rulers buried nearby. For thousands of years, domestication created both physical and genetic changes in dogs. While many of the early dogs looked quite similar to each other, new breeds were developed to meet a variety of human needs and coat colors and textures became more diverse. Many of these changes can be attributed to interbreeding and hybridization of individual dog populations, as humans moved around the planet with their canine companions and encountered new groups of canids.

Today, there are hundreds of dog breeds and most of them are not that old. They arose due to the introduction of dog shows during the Victorian era in Britain. So dogs were originally drawn to our ancestors for food, but they

eventually

joined us, working and living alongside us for thousands of years. And this bond continued even after death, according to the archaeological record of human and dog burials. But the origins of this relationship are even more complicated than scientists originally thought, and new discoveries change the history of dog domestication all the time. And we're still waiting to hear the DNA results from Dogor, that 18,000-year-old Siberian puppy.

The hope is that it can shed some light on the early days of domestication. But, at the very least, we can say that dogs have been the

best

friends

of our species for a long time. I must quickly thank David Howe, the guru of ethnocynology, for making sure he had our "puppies" in line. A big shout out to this month's incredibly awesome eontologists: Patrick Seifert, Jake Hart, Jon Davison Ng, Sean Dennis, Konstantin Haase, and Steve. All pledge levels have access to our Discord, so join us and become an Eonite at patreon.com/eons. And as always I want to thank you for joining me in the studio.

If you like what we do here, subscribe at youtube.com/eons.