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New research shows that most modern dogs, from big Shiloh shepherds to tiny chihuahuas, carry small but noticeable traces of wolf ancestry from after they were first domesticated. These lingering wolf genes may have helped shape things like size, smelling ability, and even personality.
The study, published today in the journal Proceedings of the National Academy of Sciences by a team led by researchers at the Museum and the Smithsonian’s National Museum of Natural History, suggests that this extra bit of wolf heritage could give dogs an edge when adapting to all kinds of human environments.
“Modern dogs, especially pet dogs, can seem so removed from wolves, which are often demonized,” said the study’s lead author Audrey Lin, a Gerstner Postdoctoral Scholar in Bioinformatics and Computational Biology at the Museum. “But there are some characteristics that may have come from wolves that we greatly value in dogs today and that we choose to keep in their lineage. This is a study about dogs, but in a lot of ways, it’s telling us about wolves.”
Dogs first emerged from an extinct group of gray wolves during the late Pleistocene, roughly 20,000 years ago, as they began living alongside humans. Even though wolves and dogs still share the same habitats and can have puppies together, it doesn’t happen often. Aside from a few deliberate wolf–dog crosses, researchers have found little evidence that the two groups exchanged genes after dogs split off and formed their own distinct lineage.
Using more than 2,700 published genomes of wolves, breed dogs, village dogs, and other canids from the late Pleistocene to today, the researchers explored historical dog-wolf gene flow, finding that almost two-thirds of breed dogs have wolf ancestry from crossbreeding that occurred around 1,000 generations ago.
“Prior to this study, the leading science seemed to suggest that in order for a dog to be a dog, there can’t be very much wolf DNA present, if any,” Lin said. “But we found if you look very closely in modern dog genomes, wolf is there. This suggests that dog genomes can “tolerate” wolf DNA up to an unknown level and still remain the dogs we know and love.”
Pip the shepherd mix© Audrey Lin
Linus the Boston terrier© Jose Barba-Montoya
They also found that all of the genomes analyzed from village dogs—free-roaming dogs that live in or near human settlements—carry detectable wolf ancestry.
The highest levels of wolf ancestry, between 23-40 percent, were found in Czechoslovakian and Saarloos wolfdogs, which were purposefully bred through hybridization with wolves. Among breed dogs, the most “wolfy” were the great Anglo-French tricolour hound (between 4.7 and 5.7 percent wolf ancestry) and the Shiloh shepherd (2.7 percent wolf ancestry).
The study found that wolf ancestry is higher among larger dogs and in those bred for certain types of work, including Arctic sled dogs, “pariah” breeds, and hunting dogs. Terriers, gundogs, and scent hounds have the least wolf ancestry, on average.
While some large guardian dogs have high wolf ancestry, others, like the Neapolitan mastiff, bullmastiff, and the St. Bernard, have none. Wolf ancestry is also found in a wide range of dog breeds outside of these correlations, including in the tiny chihuahua, which has about 0.2 percent wolf ancestry.
“This completely makes sense to anyone who owns a chihuahua,” Lin said. “And what we’ve found is that this is the norm—most dogs are a little bit wolfy.”
Pączki and Mrs. Prindables the pug/Chihuahua mixes© Mike Barrett
Tilly the sled dog mix© Logan Kistler
Patterns were also found in the personality terms that are used by kennel clubs to describe dog breeds. The descriptors most associated with low wolf-ancestry breeds were “friendly,” “eager to please,” “easy to train,” “courageous,” “lively,” and “affectionate.” In contrast, dogs with high wolf ancestry are more often described as “suspicious of strangers,” “independent,” “dignified,” “alert,” “loyal,” “reserved,” and “territorial.”
Other descriptors, including “intelligent,” “obedient,” “good with children,” “dedicated,” “calm,” and “cheerful” occurred with similar frequency in both groups of dogs.
The researchers note that these traits are biased assessments of breeds’ behaviors, and it is not known if wolf genes are directly responsible for these characteristics, but this finding opens paths for future research in dog behavioral science.
The study also uncovered adaptations that dogs have inherited from wolves. For example, there are enriched olfactory receptor genes in village dogs, which depend on the ability to sniff out human food waste. There is also a Tibetan wolf-like gene that helps Tibetan mastiffs tolerate low-oxygen conditions.
“Dogs are our buddies, but apparently wolves have been a big part of shaping them into the companions we know and love today,” said study co-author Logan Kistler, curator at the National Museum of Natural History. “Through the years, dogs have had to solve all kinds of evolutionary problems that come with living with humans, and it seems like they use wolf genes as part of a toolkit to continue their evolutionary success story.”