Even Chihuahuas Still Have Some Wolf In Them – Here’s How Some Dogs Still Carry That DNA

All modern-day dogs, from burly Newfoundlands to skinny Salukis, are descended from an ancient population of domesticated gray wolves. Despite the nearly 20,000 years that have passed since then, a new study published in Proceedings of the National Academy of Sciences concluded that the majority of dog breeds alive today have detectable levels of wolf DNA in their genome.

These genetic signals may contribute to traits that have shaped our relationship with dogs over millennia, including personality, sense of smell and size. The enduring ancestry of dogs, the authors of the new work write, “has shaped their evolution and conferred unique advantages for their survival in diverse human environments.”

“Modern dogs, especially companion dogs, can seem so far removed from wolves, which are often demonized,” Audrey Lin, a bioinformatician at the American Museum of Natural History and co-author of the study, said in a press release. “But there are some characteristics that might have come from wolves that we greatly value in dogs today and choose to keep in their lineage.”

Can 20,000 years separate dogs from wolves?

Dogs and wolves, although they share similar geographic ranges, rarely cross paths. This meant that previous analyzes had concluded that domestic dogs were unlikely to harbor much residual wolf DNA, Lin said. But his team’s in-depth analysis suggests that wolf ancestry is embedded in the genome of today’s dogs.

“This suggests that dog genomes can ‘tolerate’ wolf DNA to an unknown level and still be the dogs we know and love,” Lin added.

Lin’s new study explored the genomes of more than 2,700 dogs and wolves spanning 20,000 years of history, contained in the National Center for Biotechnology Information and the European Nucleotide Archive. More than two-thirds of modern breed dogs still retain DNA from a wolf cross made 1,000 generations ago. Interestingly, 100% of free-ranging village dogs living in and around human settlements had wolf ancestors.

The highest levels of wolf ancestry were found in samples taken from Czechoslovakian and Saarloos wolfdogs. These high levels are not surprising, as the breeds were created by deliberately crossing German Shepherds with Carpathian and Siberian gray wolves, respectively.

Among dogs without a history of intentional crossbreeding, samples from two dogs from the Grand Anglo-Français Tricolore led the way, with 5.7 percent and 4.7 percent wolf ancestry, respectively. These findings were surprising, because these dogs, the most common hounds in modern France, have no recognized history of interbreeding with wolves.

Trends in wolf DNA

Additionally, the Grand Anglo-Français Tricolore had the highest variance of all breeds analyzed, with some other dogs of the same breed containing very low levels of wolf DNA. The two outlying Tricolors contained far more wolf ancestry than even the Tamaskan dog, which was created by combining various Arctic dog breeds to develop a superficial wolf-like appearance. The Tricolor, Tamaskan, and Shiloh Shepherd were the only breeds to contain more than 2 percent wolf ancestry.

The study also revealed broader trends. Wolf DNA levels were higher in larger dogs and those bred for sled work. The team found the lowest average levels of wolf ancestry in terriers, hounds and scent hounds. Larger guard dogs generally had low wolf ancestry, although a small number of individuals with high ancestry levels skewed their average.

The tiny chihuahua, on the other hand, had an average of 0.2% wolf ancestry.

What words make a dog more like a wolf?

The team also analyzed which words were used most and least to describe large and small dog breeds. Dogs with strong wolf ancestry were likely to be described as “wary of strangers,” “alert,” “loyal,” and “territorial.” In contrast, breeds with low wolf ancestry were most often described as “friendly,” “eager to please,” “easy to train,” “brave,” “lively,” and “affectionate.” Any link between these behaviors and wolf DNA is purely correlational. The team says additional studies are needed to establish causation.

The team identified two specific cases in which certain dog breeds benefited from wolf ancestry. Tibetan mastiffs have a high level of a wolf-derived gene that allows them to tolerate low oxygen levels in their high-altitude territory. Some village dogs had olfactory receptor genes with high wolf ancestry. These free-roaming dogs must be able to sniff out food to survive.

“Dogs are our friends, but apparently wolves played an important role in transforming them into the companions we know and love today,” Logan Kistler, study co-author and curator at the National Museum of Natural History, said in the press release.

Learn more: Why there is the leader of the wolf pack

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