Although dogs(Familiar wolf dog) and wolves (dog lupus) can interbreed and produce fertile offspring, hybridization between them is much less common than between domestic and wild populations of other species. In the new study, scientists from the American Museum of Natural History, the Smithsonian National Museum of Natural History and the University of California, Davis, combined highly sensitive local ancestry inference and phylogenomic analysis of genomes representing 2,693 ancient and modern dogs and wolves. They found that 64.1% of modern dog breeds have wolf ancestry in their nuclear genome as a result of admixture dating back nearly a thousand generations, and all free-ranging dog genomes analyzed carried some ancient wolf ancestry.
German Shepherd puppy. Image credit: Marilyn Peddle / CC BY 2.0.
“Modern dogs, especially domestic dogs, may seem so far removed from the often demonized wolves,” said Dr. Audrey Lin, a postdoctoral fellow at the American Museum of Natural History.
“But there are some characteristics that may have come from wolves that we value in dogs today and that we prefer to keep in their bloodlines.”
“This study is about dogs, but it tells us a lot about wolves.”
Dogs evolved from a human-influenced extinct population of gray wolves in the late Pleistocene, about 20,000 years ago.
Although wolves and dogs live in the same geographic regions and can produce fertile offspring, hybridization is rare.
And, with the few exceptions of intentionally interbreeding wolves and dogs, there is little evidence of gene flow between groups after the domestication of dogs split their gene pools.
“Before this study, leading scientists seemed to assume that for a dog to be a dog, it did not have to have very much, if any, wolf DNA,” Dr. Lin said.
“But we found that if you look closely at the genomes of modern dogs, the wolf is there.”
“This suggests that dog genomes can carry over wolf DNA to unknown levels and still be the dogs we know and love.”
The researchers examined the historical gene flow of dogs and wolves using 2,693 published genomes of wolves, pedigree dogs, country dogs and other canids, spanning the late Pleistocene to the present, from the National Center for Biotechnology Information and the European Nucleotide Archive.
They found that 64.1% of pedigree dogs have wolf ancestry in their nuclear genome as a result of crossbreeding that occurred about 1,000 generations ago.
In addition, all of the analyzed genomes of village dogs—free-roaming dogs living in or near populated areas—carry detectable wolf ancestry.
Czechoslovakian and Saarloos wolfdogs, which were purposefully bred by hybridization with wolves, had the highest level of wolf ancestry, with 23-40% of their genomes.
Among the pedigree dogs, the most “wolf-like” were the Great Anglo-French Tricolor Hound (from 4.7 to 5.7% of wolf origin) and the Shilon Sheepdog (2.7% of wolf origin).
While the Shiloh Sheepdog originated from breeding of wolfhounds or other recent dog-wolf hybrids to create healthier, more family-friendly shepherd dogs in the United States, the origin of the extensive wolf ancestry in the Great Anglo-French Tricolor Hounds—the most common hound in modern France—is unknown and unexpected.
The Tamaskan, a “wolf-like” breed that originated in Britain in the 1980s through selection of huskies, malamutes and other breeds to create a wolf-like appearance, has about 3.7% wolf ancestry.
The scientists found several patterns in the data: wolf ancestry was higher in larger dogs and in dogs bred for certain types of work, including Arctic sled dogs, rogue breeds and hunting dogs.
Terriers, pointers and hounds have, on average, the least amount of wolf ancestry.
While some large guard dogs have high wolf ancestry, others, such as the Neapolitan Mastiff, Bullmastiff, and St. Bernard, have no detectable wolf ancestry.
Wolf ancestry is also found in a wide range of dog breeds not included in these correlations, including the tiny Chihuahua, which has about 0.2% wolf ancestry.
“This makes sense for anyone who has a Chihuahua,” Dr. Lin said.
“And we found that this is the norm—most dogs are a little wolfish.”
The authors also compared how often kennel clubs used personality terms to describe dog breeds with the highest and lowest levels of wolf ancestry.
The descriptor most associated with low wolf breeds was “friendly”, followed by “eager to please”, “easy to train”, “bold”, “lively” and “gentle”.
In contrast, dogs with high wolf ancestry are more often described as “suspicious of strangers”, as well as “independent”, “dignified”, “vigilant”, “loyal”, “stand-offish” and “territorial”.
Other descriptors, including “smart,” “obedient,” “good with children,” “loyal,” “calm,” and “fun,” occurred with equal frequency in both groups of dogs.
The team emphasized that these traits are biased estimates of breed behavior and it is unknown whether wolf genes are directly responsible for these characteristics, but this discovery opens the way for future research in canine behavioral science.
In addition, the researchers discovered important adaptations that dogs gained access to through wolves, including: enrichment of wolf ancestry for olfactory receptor genes in village dogs, which depend on the ability to sniff out human food scraps; and the spread of the Tibetan wolf-like gene, which helps Tibetan mastiffs tolerate low-oxygen conditions in the Tibetan Plateau and Himalayas.
“Dogs are our friends, but wolves clearly played a large role in shaping them into the companions we know and love today,” said Dr. Logan Kistler, a researcher at the National Museum of Natural History.
“Over the years, dogs have had to deal with all sorts of evolutionary challenges associated with living with humans, whether it's surviving at high altitude, finding their next meal while free to roam the countryside, or protecting the herd, and they appear to be using wolf genes as part of their toolkit to continue their evolutionary success story.”
conclusions were published this week in Proceedings of the National Academy of Sciences.
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Audrey T. Lin etc.. 2025. A legacy of genetic connections to wolves shapes modern dogs. PNAS 122 (48): e2421768122; doi: 10.1073/pnas.2421768122
