Full disclosure: the information below about canine domestication and the fox experiment was written largely from memory, and as both are ongoing studies, they might have updated information in the future. Again, these are just my thoughts from study of canine history and observance of modern life with domestic dogs – not a study or meant to be anything other than thought-provoking and thought-sharing! Additionally, I am aware that there have been some challenges to the Farm Fox Experiment, and while both valid and interesting, I still feel this experiment has merit. It’s important to remember, when considering that experiment, that signs of domestication, “domestication syndrome,” increasing tameness, etc. do not mean actual domestication.

Dogs are such a big part of the human experience that you’d think we’d know everything about how the relationship between our species happened. Unfortunately, that’s not the case! Science is still out on exactly when domestication officially happened, as well as when wolves started the process, and even where it happened. Even the actual ancestor wolf is a bit of a mystery! We know it was a wolf species related to both modern grey wolves and domestic dogs, and that it is now extinct, but not much more. (That’s right, not only is your dog absolutely not a grey wolf in a dog costume, it’s also not a direct descendant of these modern wolves.)

As research on canine DNA continues to evolve and areas long frozen over thaw, we’re learning more than ever before about this incredible relationship. We’ve uncovered new possible origin points for domestication, and more exciting finds of ancient canines that were no longer entirely wolf, properly, but also were not quite domestic dogs either. While some things might remain a mystery forever, it’s likely only a matter of time before we find at least one site in the world with the first genuinely domestic dogs.

What we do know for sure? In addition to consistent evidence pointing to our relationship with dogs skewing toward companionship, and that the animals played a more active role in the process, Domestication takes a really long time.

The estimates on exactly when it happened are extreme: up to 30,000 years ago to only 15,000. That doesn’t account for the time it took dogs to…well, become dogs. To evolve into a legitimate, genetically unique domestic species. We have no idea how long wolves were hanging around increasingly closely to humans, how many times one or more made the journey into our camps, stayed, and bonded with us. How long they were simply tame wolves that hung around us, both species having a symbiotic relationship. How long “protodogs” (serious changes from wolf anatomy and treated more like modern dogs by humans, but still genetically not domestic dogs yet) lived with and were loved by us before they were officially dog-dogs.

In 1959, a fascinating experiment began that could shed light on the domestication process. The Farm-Fox Experiment in Russia took foxes from fur farms and selectively bred those with lower fear and aggression toward humans, both critical components of domestication. (An opposite group was selectively bred for the opposite, human reactivity and aggression.) It was possible that domestication might proceed more quickly with these foxes, as the goal of domestication was defined, pursued intentionally, and made the sole focus of the project. Domesticating species like dogs and cats was unlikely to have been such an intentional process – it’s most likely that both species started and controlled the domestication process themselves in the beginning, hanging around us for easy food and some protection, and like us, increasingly going for companionship and familial relationships that kept being mutually beneficial to all. Pre-dog wolves who were too fearful of humans weren’t going to hang around us; those who were too aggressive or predatory weren’t going to be tolerated by us. Those who were more naturally good around us received benefits that allowed them to survive and procreate, creating another generation of human-inclined wolves. This is a different process than our domestication of animals like horses, which came later and was more intentional…since we wanted to be weird and ride around on them, and they’re a prey animal. (Seriously, horses, I can’t thank you enough for tolerating our utterly bizarre nonsense; we absolutely don’t deserve horses and all they’ve given our species!)

So, yes, in theory, the Russian experiment could’ve yielded more expedient results than 15,000+ years.

And, for a little bit, it seemed like that was going to be the case. It looked like domestication could actually be a much shorter process than we’d ever imagined. Because it didn’t take long before the foxes bred for tameness were showing distinct physical differences and even behavioral ones.

Domestication can have some commonalities, like coat mutations and neoteny. Coat colors and patterns that would never do well in the wild appear, like spots, dilute colors, and so on. And, for a few reasons, features present only in baby animals start sticking around: floppy ears, big eyes, shorter muzzles. That’s neoteny: the retention in adults of traits previously seen only in the young. This is a big deal in evolutionary biology and the study of domestication. It impacts behavior as well, keeping behaviors more like those of young animals, like a greater willingness to bond with other species and to embrace novel experiences. In dogs today, this is why we not only have “puppy dog eyes,” but also a species with an extended period of social learning that allows them to best adapt to our very strange world when we take advantage of teaching them about it.

Foxes very quickly began to display curly tails, floppy ears, spotted coats, and behaviors like seeking out human affection and companionship. How quickly? About ten years. This would certainly seem to upend what we’d previously thought about domestication, and in some ways, it did! We do now know that these changes can occur much faster than we thought, and it does reflect the changes we see in the remains of pre-dog wolves that we find.

But these foxes were not domesticated.

It is now 2026, and the experiment is still ongoing. When it became widely publicized in the early days of the internet, it created quite an interest in buying these foxes. The experiments did, and do, selectively sell foxes both as pets and to other studies; after the fall of the Soviet Union, the lack of funding meant foxes could be sold for fur or for pets to keep the project and its residents fed and cared for. Just importing one of these foxes runs about $9,000, never mind the cost of the fox itself, making the Russian foxes seriously cost-prohibitive. However, others certainly jumped at the opportunity to offer captive-bred foxes to cash in on the “Russian domestic fox” craze. Today, this remains a problem. There are no domesticated foxes, just captive-bred ones that, in the best scenario, have been bred for generations for tameness. While they would do better in a captive life with humans than one plucked from the wild, they still require so much specialized care and keeping that the majority of people are not prepared to give or capable of giving. This includes the actual Russian foxes!

If for no other reason, I can attest to the fact that foxes tend to smell quite badly, and for Fox Reasons, they pee in water dishes. Just an FYI on why you do not actually want a pet fox.

They’re still just really cute and beautiful foxes that are way more friendly and companionable with people, not domestic pets.

Domestication, fortunately or unfortunately, remains something that takes a REALLY long time to result in a legit, genetically domesticated companion animal! It’s also something that we’ve tried with so many other species throughout history (including foxes, who our ancestors did live with like the wolves and protodogs), not every species is applicable.

What does this have to do with “littermate syndrome?”

It’s further evidence that allows us to imagine just how long human beings have shared our lives with these animals. From wolves willing to take a chance on us to protodogs was a long time. Then, as many as 30,000 years ago, the genuinely domesticated dog happened.

From our earliest days on, our relationship with dogs has been more familial than recent history might lead us to believe. Though the viewpoint on and treatment of dogs certainly have always varied in different cultures and times, often an ebb and flow of love and humane treatment (or not) that followed patterns of our own species’ shifting fortune, ego, religion, and lifestyles, dogs have been part of the family more often than not. For example, reading the engravings on burial sites for dogs in ancient Rome is a lot like reading pet memorials today, filled with the uniquely aching love of losing a beloved pet. It’s the same in many written records we have of dogs; at some point, someone put down their virtues, the great love of them, their humor, their value beyond working tasks. Even poetry and statements lamenting that we are not more like dogs.

These seemingly modern-era sentiments hint at what we could’ve already guessed: we didn’t just spend a long time beside the ever more refined dog, we have spent a long time in close relationships with them.

Yet, there is no mention of “littermate syndrome.” We can easily recognize some behaviors and behavioral problems that have been written about, even unintentionally, and certainly without the jargon, but this one is lacking.

Most historical dogs performed some manner of work, and breeding dogs that would excel in their niches was critical. Even if people weren’t allowing their herding, flock guardian, spaniels, retrievers, and guard dogs to come sleep in the bed with them, they were spending a lot of time with them. Physical and behavioral working traits are absolutely inherited, as anyone with a working breed in a pet home today will tell you (howdy, Tater), but all of these dog-jobs still require training and refinement. Then, the work itself, only guardian jobs tend to be done without any human involvement. We were spending a lot of time breeding, training, assessing, and working with our dogs!

And, in a world where spaying was nonexistent and neutering extremely rare and strange, where we did not yet have overflowing animal shelters everywhere, litters were commonplace – planned and otherwise. We were far more familiar once with litters of puppies, and when raising them for jobs, as was more common then, we were not getting rid of them ASAP. Littermates stayed together longer for their aptitude and health to be apparent, and to begin training for the tasks they’d take on. They also stayed together for life more often. Quality, skilled working dogs were the difference between survival and doom. They were expensive, and if you could afford to raise your own and keep backups (dogs become ill, they get injured, they have litters, and they need to be rotated) or the next generation to take over for an inevitably retiring dog, that was wisest and most economical.

This means that not only have we, as a species, spent a huge portion of our own time on this planet with dogs, but also that we spent most of that time engaged with them. We weren’t getting a pet and letting toys and the backyard do most of the work for us while we were away for a whole day, five days a week, nearly all year long. (Or, while we spent more time with our screens than our canine companions.) We were once more actively engaged in life with dogs, even when our knowledge of them and humane treatment was often far poorer.

I find it unthinkable that we would not have noted and put some name to “littermate syndrome” thousands of years before now if this were a real and destined problem.

Instead, I think that knowledge of our long, shared history strongly implies that “littermate syndrome” and the real problems of raising multiple same-age puppies are a more modern issue. It must at least be far more prevalent in modern times.

I have no doubt that, over the course of all this time, people have dealt with the pitfalls of raising two or more puppies together, related or not. That is ‘something probably destined to happen, not because of littermates or because of dogs at all, but because of people. We tend to take on more than we can or know how to handle. It would be improbable to think that no one in history failed to give two same-age puppies enough individual training, exposure, alone time, and general support for growing up into two well-adjusted adult dogs! We likely don’t hear about these incidents due to a lack of contextual knowledge, and that being a “problem dog” was often fatal.

That this began appearing as A Thing so recently is, in my opinion, a symptom of modern pet guardianship, and how it so often clashes with what dogs (as a species, among breed needs, and as individuals) truly need to be resilient, successful adults living good lives. We are, without question, more attentive to humane welfare, and the fact that we care so deeply for our dogs is evident in the booming pet industry. In a perfect world, we would keep the progress while going back to being able to spend so much more time with our dogs. Real, undistracted, together time. I doubt we would have much issue with “littermate syndrome” if that were possible!

What do you think about the topic of “littermate syndrome” from this historical vs modern perspective? Share your thoughts in the comments!

Want to know more about the Russian foxes? This fascinating topic has been widely covered in articles and videos, and like any topic of interest and importance, it even has various debates. Here are just a few things to get you started:

Early Canine Domestication: The Farm-Fox Experiment, Lyudmila Trut (geneticist involved in the experiment), American Scientist, March-April 1999

Russia’s Experiment Turned Wild Foxes into Pet Dogs in 60 Years, YouTube video by Wild Versus

We met the world’s first domesticated foxes, YouTube video by Verge Science