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That the dog is from a wolf derived is by now as close to scientific consensus as a theory gets. But consensus blows apart when it comes to naming the wolf or wolves involved. Usually, the generic gray wolf, Canis lupus, is invoked as the parent species in one of its three major Eurasian guises—European gray wolf; Middle Eastern wolf, also known as the Arabian wolf; or the Chinese wolf. But to date no one has definitively identified the wolf or wolves who gave rise to the dog, and without the wolves, they are unlikely to find the place or places where it happened.
The result is a running battle, with teams of researchers promoting southeastern China, the Middle East and/or various parts of Europe as centers of dog domestication. Some theories allow for multiple places of origin; others demand only one. Dates proposed for emergence of the dog now range from 135,000 to 14,000 years ago.
Now, a new paper by an international team of geneticists suggests that the wolf from which dogs derive has not been found because it no longer exists. The researchers propose that a now extinct “basal wolf” gave rise to living wolves and dogs who went their separate evolutionary ways 11,000 to 16,000 years ago, although they continued ‘admixing’ for some time thereafter. In fact, although principal author Adam Freedman, a Harvard geneticist, does not say it outright, wolves and dogs continue to admix, albeit at a low level.
Freedman, corresponding author John Novembre, now at the University of Chicago, and their collaborators count three years as a wolf and dog generation and assume a constant mutation rate to calculate their dates—that is standard procedure for evolutionary geneticists But use a different mutation rate with a two-year generation time, they say, citing another study, and the dates get pushed toward 72,000 years ago for the divergence of dogs and wolves from their common ancestor.
Novembre and his colleagues observe that no matter what date is used, dogs were born into the society of hunters and gatherers not agriculturalists. In making that observation the researchers pointedly correct the most recent false information—published amidst much hoopla by Nature earlier this year and challenged many places including here. The authors of the Nature paper asserted that increases in the number of copies of a gene coding for amylase, an enzyme involved in digesting carbohydrates, occurred among sniveling dump-diving wolves who then became dogs when humans started farming. As a result dogs have multiple copies of the gene, AMY2B; wolves do not, the researchers said. They were wrong.
The Novembre group looked again and saw that dingoes had two copies of the gene and Siberian huskies had three to four. The Saluki, a dog of the Fertile Crescent and, thus, agriculture, had 29, and some wolves had 14 to 16, proving that domestication was not contingent on extra copies of a gene for digesting starches.
Confirmation of the dog as a creation of hunting and gathering cultures and evidence of prolonged interbreeding with wolves led Novembre and his colleagues to suggest that a new approach is needed for understanding the dog’s creation. The old models have failed. They failed long ago.
Novembre and his colleagues based their research on analyses of just over 10-milllion single nucleotide variant sites from full genome scans of six “representative” animals—a dingo, a basenji, a Croatian wolf, an Israeli wolf, a Chinese wolf, and a golden jackal, once commonly and still occasionally wrongly considered to be the parent species of pariah dogs. The Australian dingo and African basenji were chosen because each became resident in a place lacking wolves with whom they could interbreed, meaning that any crossbreeding they did with wolves had to be older than when they became isolated in Australia and Africa. The researchers chose the wolves believing they represented the prime areas for the first dogs to appear. The researchers say that the resolution obtained in their scans, which provided the greatest genomic detail to date, allowed them to use such a small number of animals.
Elsewhere in their paper, Novembre and his colleagues discuss some sites they found on the dog genome that have to do with neurological, metabolic, and physical development, as well as gene regulation, but for now whether these even have any real significance is unknown.
In their search for the wolfish first dog, the scientists found murkiness, not clarity. In fact, they could find no proof that any of their wolves was more related to dogs than any other, and that led them to conclude that the basal wolf no longer existed. Nonetheless, they say the evidence shows that the dog was domesticated in one place, and that following their split, dogs and wolves experienced genetic bottlenecks, with dogs being subject to a severe 17 to 49 percent reduction after their separation from wolves. The bottleneck wolves went through was less severe but no less real.
It seems clear that the only way to get a fix on ancient dogs and wolves is through their DNA, and a number of groups are trying to do just that. It is difficult to obtain uncorrupted segments of ancient DNA long enough to work with. People with samples guard them zealously, but the potential pay off in terms of knowledge is large.
I hope that at least one group is attempting to analyze some of the wolf fossils found since about 500,000 years ago in association with Homo erectus,because if the point is to find a workable explanation for the transformation of wolves to dogs, then we might as well start as far back as possible—to the time a coyote-sized wolf, Canis mosbachensis, or sometimes C. lupus mosbachensis, is thought to have evolved into the larger gray wolf.
Mosbachensis fossils appear frequently enough in proximity to Homo erectus that it is hard to imagine them not having a relationship of some sort. I talk about this prospect and others in How the Dog Became the Dog and conclude that although it is difficult to perceive a straight line of descent through several species of early humans, including Neanderthal, and over hundreds of thousands of years, it is not difficult to conceive archaic Homo sapiens and later our own subspecies entering a world where some populations of wolves were predisposed to consorting with naked bipeds—that is some wolves and humans were highly sociable, even hypersociable in that they needed company.
Dogs would have come from such a population, and in the process of becoming might have affected certain personality characteristics of the wolf population from which they were drawn. Thus, while sociable wolves were removed from the general population and brought more closely into the human domain, unsociable ones were left in, or return to the general pool—or were killed. By rights, those wolves would have become prone to avoiding people and more unsociable than before, even without humans hunting them.
The key word here is “sociability,” which I take as a desire, a need, to be with other, kindred beings, and the capacity to move past fear of the different other, not only to accept but to care for them. Put another way, the humans who helped create dogs had the capacity to accept sociable wolves into their family and sociable wolves had the capacity to substitute human society for their pack in ways that benefitted both by providing increased physical security and food security in lean times.
This scenario involving long association with various ancestral humans runs through Neanderthal, Homo neanderthalensis, the consummate Ice Age hunter. A decade ago, Austrian ethologists Wolfgang Schleidt and Michael Shalter published a lengthy essay in the journal Evolution and Cognition (2003) titled “Coevolution of Humans and Canids: An Alternative View Dog Domestication: Homo Homini Lupus?” In it, they argue that Ice Age wolves were the first pastoralists because of their habit of constantly shadowing reindeer herds and keeping them healthy, the way a good shepherd would, by culling the old, the sick, the infirm, and the very young. Humans moving out of Africa into Eurasia learned how to shadow prey from wolves, and they also learned about cooperation, deference, and the art of knowing one’s place in the pack or family from wolves.
Schleidt and Shalter argue that in that sense it is more appropriate to speak of wolves becoming dogs in the process of domesticating humans. In any event, they note that the relationship of wolves and humans was mutually beneficial.
Whether a basal wolf exists will be debated for some time unless someone gets lucky and finds it or the need for it vanishes. The more I think on it, the more it seems an invention to solve a particular failure of imagination.
Novembre and his colleagues correctly observe that the dog is a creation of hunting and gathering people but then plant those people in a hypothetical place with a hypothetical population of now extinct wolves. Next time, they might want to put wolves, dogwolves, and people in motion following the animals they hunted. The dog was born on the trail with its people. I have ideas about who those people might have been, but that is for another time. For now, it seems reasonable in the search for the origins of the dog to consider where people were going. The dog, after all, does not exist without them.
