The prevailing theory states that dogs originate from gray wolves, and in recent years continuous research has been conducted to map this evolutionary path. The latest study reports that two-thirds of today’s purebred dogs retain the genes of the wolves from which they descend.
Although dogs and wolves can interbreed and produce fertile offspring, hybridization between them is far rarer compared to domestic and wild populations of other species.
In a 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 methods and phylogenomic analyses using genomes representing 2,693 ancient and modern dogs and wolves.
In their publication in the journal Proceedings of the National Academy of Sciences, the researchers report that 64.1% of modern purebred dogs have wolf ancestry in their nuclear genome from admixture that occurred nearly a thousand generations ago, and that all examined genomes of living dogs contain some ancient wolf ancestry.
“Modern dogs, especially pets, may seem so far removed from wolves. Yet there are traits that may come from wolves which we value greatly in dogs today and choose to maintain in their breeding lines. This is a study about dogs, but in many ways it tells us about wolves,” says Dr. Audrey Lin, postdoctoral researcher at the American Museum of Natural History.
The background
Dogs are believed to have evolved from a now-extinct population of gray wolves under the influence of humans during the Late Pleistocene, around 20,000 years ago.
Even though wolves and dogs live in the same geographic regions and can produce fertile offspring, hybridization remains rare. With a few exceptions of intentional wolf–dog crossbreeding, there is little evidence of gene flow between the groups after domestication separated their gene pools.
“Before this study, the prevailing scientific view suggested that for a dog to be a true dog, it should have almost no wolf DNA. But we found that if you examine modern dog genomes very closely, the 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,” says Lin.
The researchers investigated the historical gene flow between dogs and wolves using 2,693 published genomes from NCBI and the European Nucleotide Archive, including wolves, purebred dogs, and other dog species from the Late Pleistocene to today.
They found that 64.1% of purebred dogs have wolf ancestry in their nuclear genome from interbreeding that occurred about a thousand generations ago. Furthermore, all genomes of free-ranging dogs living near human settlements show detectable wolf ancestry.
The Czechoslovakian Wolfdog and the Saarloos Wolfdog—both created through intentional wolf–dog crossbreeding—had the highest wolf ancestry levels, between 23% and 40%. Among purebred dogs, the most “wolf-like” were the large tricolor Anglo-French hound with 4.7–5.7%, and the Shiloh Shepherd with 2.7%.
The Shiloh Shepherd emerged from crosses with wolfdogs or other recent dog–wolf hybrids to create healthier and more family-friendly dogs in the United States.
The origin of the extensive wolf ancestry in the large Anglo-French tricolor hound, the most common hunting dog in modern France, is unknown and unexpected.
Tamaskan dogs, a breed with wolf-like features created in Britain in the 1980s through selective breeding of huskies, malamutes, and others to resemble wolves, have about 3.7% wolf ancestry.
Patterns
The scientists identified several patterns in the data: wolf ancestry is higher in large dogs and in those bred for specific tasks, such as Arctic sled dogs, certain pariah breeds, and hunting dogs.
Terriers, gundogs, and scent hounds on average have the lowest wolf ancestry. While some large livestock guardian dogs have high wolf ancestry, others—such as the Neapolitan Mastiff, Bullmastiff, and Saint Bernard—show no detectable wolf ancestry.
Wolf ancestry is also found in a wide range of other breeds, such as the tiny Chihuahua, which has about 0.2%.
“This makes perfect sense to anyone who has a Chihuahua, and what we discovered is that this is the rule—most dogs are a little bit… wolf,” says Lin.
The authors also compared the frequency of personality descriptors used by kennel clubs to characterize breeds with the highest and lowest wolf ancestry. The descriptors most associated with low wolf ancestry were “friendly,” followed by “eager to please,” “easy to train,” “bold,” “lively,” and “affectionate.”
Conversely, breeds with high wolf ancestry are more often described as “wary of strangers,” “independent,” “dignified,” “alert,” “loyal,” “reserved,” and “territorial.”
Other descriptors, such as “intelligent,” “obedient,” “good with children,” “devoted,” “calm,” and “cheerful,” appear with similar frequency in both groups. The team emphasized that these traits are subjective assessments of breed behavior and it is not known whether wolf genes are directly responsible for them, but this finding opens pathways for future research in canine behavior science.
Adaptations
Additionally, the researchers identified significant adaptations dogs acquired through wolves, such as enriched wolf ancestry in olfactory receptor genes in free-ranging rural dogs that rely on the ability to detect human food waste, and the presence of a gene similar to that of the Tibetan wolf which helps Tibetan Mastiffs withstand low oxygen levels on the Tibetan Plateau and in the Himalayas.
“Dogs are our friends, but clearly wolves have played a major role in shaping them into the companions we know and love today. Over the years, dogs have had to solve various evolutionary problems that accompany cohabitation with humans—whether surviving at high altitude, searching for food while roaming freely in a village, or protecting livestock—and it seems they use wolf genes as part of a toolkit to continue their evolutionary success story,” says Dr. Logan Kistler, researcher at the National Museum of Natural History.