Why the Transformation of Wolves to Dogs Remains a Puzzle
In the search for answers to the dog, the human factor should not be discounted.
Posted May 21, 2013
The more I consider the continuing debate over the “time” and “place” for the transformation of wolf into dog, the more I become convinced that the puzzle remains unsolved because of human devotion to a simplistic, clever-sounding idea that never made sense in the first place. As first put forth by Raymond Coppinger, that idea was that wolves feeding on the garbage piles of quasi-permanent Mesolithic villages grew tamer over the course of generations until they no longer feared or threatened humans. In the process of taming themselves, those wolves also became less fearful of and aggressive toward humans. They were cute, too. For reasons that were never clear to me, people took these cute obsequious dump divers into their homes, where they blossomed into dogs.
Coppinger pinned his argument on Dmitry Belyaev’s experiment, begun in 1959, at a Siberian fur farm, in which a group of foxes was bred for tameness alone and within ten generations was producing foxes that resembled dogs with floppy ears, piebald coats, and a high need for attention. They were juvenilized in behavior as well as appearance.
There are a number of reasons why the foxes are not a good model for origins of the dog, and I have elsewhere addressed them in detail. For now, suffice it to say that dogs arose not in quasi-permanent Mesolithic villages but in Paleolithic hunting camps. They were not sought nor selected because they solicited attention and showed no aggression—these are hardly traits of a good guard, which was one of the tasks of early dogs. Guarding remains a major reason why people keep dogs.
But the greatest problem with the self-domesticating theory is that it shuts the most creative creature on the planet out of the process. To put it bluntly, that makes no sense. Humans have always collected, tamed, and trained animals. It is inconceivable that they would ignore one as intelligent and inquisitive as the wolf.
Genomics and its offspring have shown that living organisms are not biological machines but energetic systems supported by layers of complexification. Genomics has also contributed to a more dynamic view of “domestication” as a process involving the interplay of biological, environmental, and cultural forces. The hard line between “domestic” and “wild” –always imaginary but not less real for that—has for the dog become increasingly difficult to find despite the distortions that define the current period of breedism. I am using “breedism” to refer to all aspects of the cult of the purebred dog that began to take hold about 200 years ago. Of course, there are significant differences between dogs and wolves, when they are in their own environments, but what happens when the dog goes native or the wolf becomes a lay-about?
It sometimes appears that every new find simply raises new questions while leaving old ones unresolved. That trend is apparent in two new papers by Ya-ping Zhang, a leading Chinese geneticist, who collaborated with geneticists from China and two different labs in Sweden and California on two new papers promoting Chinese indigenous dogs—native or village dogs—as the closest dogs to the ancient type.
Working with Peter Savolainen, of Sweden’s Royal Institute of Technology, Zhang has over the past decade or so insisted that dogs originated in southeast China no earlier than 16,000 years ago, and many researchers elsewhere adopted his argument despite the notable absence of dog or wolf remains from that region at that date and the presence of dog remains from other places considerably earlier.
The researchers redid the numbers using new chips that spot changes in the genome including so-called single nucleotide polymorphisms, or SNPs, and indels—insertions or deletions of small amounts of genetic material. SNPs and indels can be used to measure degrees or years of separation of discrete groups of organisms. Crunching the numbers and running regression analyses, they found that southeast China village dogs separated from wolves 32,000 years ago. There were a lot of them by then, too, they reported in an article in Nature Communications [subscription required], with Guo-dong Wang and Weiwei Zhai as first authors and Zhang as senior author—8,500 dogs by their estimate.
The new date fits nicely with some “early dogs” identified from the Altai Mountains, Belgium and the Czech Republic, although Zhang and his colleagues are not quite willing to admit that those animals are dogs. In fact, they appear to want to deal with the early date by using it to mark the beginning of a long period of self-domestication for a group of scavenging protodogs.
Zhang’s group declares: “Early wolves might have been domesticated as scavengers that were attracted to live and hunt commensally with humans. With successive adaptive changes, these scavengers became progressively more prone to human custody. In light of this view, the domestication process might have been a continuous dynamic process, where dogs with extensive human contact were derived from these scavengers much latter [sic] when humans began to adopt an agricultural life style.”
The operative words here are “commensally” and “scavenger.” Together, they say that wolves were drawn to human garbage or some other waste and so started hanging around and hunting with them but without having a discernable effect or bringing them any benefit—thus, the term “commensally”—until the biped started farming. Then the scavengers showed their true worth as crossover omnivores and became dogs.
That is not complex, but it is convoluted. At a basic level, it is not clear why protodogs could not have arrived in southeastern China from the Altai Mountain region, for example, where the people who would come to enter the New World and spread through much of the Old World as the glaciers began to retreat, had gathered, presumably with dogs some 35,000 years ago. A population of dogs and people could easily have gotten to southeast China and radiated outward from there. The much trumpeted diversity of dogs in the region could be a result not of their origins there but an accident of geography and history, including intensive breeding of dogs for food and a settlement pattern that featured many small riverine villages along the Yangtze River, one of the world’s largest.
Zhang’s defense for the lack of wolves in southeast China is that wolf populations have changed everywhere, and so no one has an ancestral wolf for study and comparison. But the Chinese indigenous dogs and a couple of related breeds, are the dogs closest genetically to wolves, and that makes them all the more important as living artifacts, Zhang and his team reason. Specifically, they looked for genetic loci that might show positive selection pressure in dogs and humans and therefor might represent parallel evolution in the two species. The genes they identified as likely candidates are involved in diet, specifically the ability to digest grains; metabolism; cancer and neurological processes, especially some involving the neurotransmitter, serotonin.
Zhang is also corresponding author with Dong-Dong Wu, both of the Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China, on a Molecular Biology and Evolution paper involving the laboratory of Robert K. Wayne, dean of canid evolutionary biologists, and several of the next generation of dog geneticists who have already published important work—Bridgett vonHoldt and Adam Boyko. They were especially focused on the prefrontal cortex and on parts of the brain that appear involved in fear response and sociability.
I say “sociability”, but, following Zhang’s lead, the researchers on these pages say “tameness,” while continuing to cling to the Soviet fox experiment as evidence that the dog was self domesticating, becoming obsequious and ingratiating and nonaggressive while eating garbage and offal. Standard descriptions of this work are abundant, and I won’t repeat them here. But it is fair to say that grand pronouncements about the working of the brain must be treated cautiously.
Most of these searches for genes involved in the transformation of wolves to dogs are based on at least two significant, faulty assumptions about the behavior of dogs and wolves. The first faulty assumption Is that wolves are now, and were in the late Pleistocene, aggressive competitors with humans. There is evidence documenting not only friendly but also mutually beneficial relationships of humans and wolves going back thousands of years. There are suggestive associations of wolf and Homo erectus remains going back hundreds of thousands of years.
The second faulty assumption is that a group of wolves effectively said to humans, “Because we like your leavings so much, we will stop vying with you and aggressing against you. We will be abject before you if you will give us excretia to eat because we cannot live by ourselves.” The question I always ask is, would you want such a creature in your house, in your bed? That is unlikely. This assumption is faulty because there is no evidence that wolves generically dislike or even fear humans. The global wolf recovery with wolves living in ever closer proximity to humans proves that wrong. It is humans who hate wolves.
That wolves and humans, similar as they are in so many ways, should make common cause, should surprise no one. Hunters study hunters. Species cooperate. It would be more aberrant if they did not. Coral groupers, Napoleon wrasse, and moray eels were recently shown to hunt cooperatively, for example. Around the world, hunting cultures had dogs that often interbred with, sometimes were indistinguishable from wolves. In the New World and elsewhere that situation was contemporaneous with the rise of multiple refined breeds in the Anglo-English speaking world.
In a real sense, then, what we call domestication of the wolf was really a rolling and flexible bringing into human culture of wolves who had the psychological and emotional capacity for sociability, for forming strong bonds not just with another individual but also with another species.
Some years ago Adam Miklosi and his colleagues compared hand reared wolves to dogs. The lengthening of the first critical socialization period and a greatly increased capacity to form strong bonds to another species were clearly central to the appearance of the dog, they concluded.
Yet for all of their problems, these two new studies are useful for their focus on indigenous dogs, the landrace dogs who although they might have several uses are generally not bred by humans to any purpose, but who still live, reproduce, and die in human society. How ancient or basic these dogs are is not really known. But they are found around the world, and I think that comparative studies of them and resident wolves and truly self-sustaining feral dogs, where they still exist, will prove most interesting. The same applies to comparison of DNA from ancient dogs and wolves. We do not yet see them clearly.