While interbreeding between canines (Canis lupus familiaris) and their wild progenitors, wolves (Canis lupus), can yield viable offspring, such hybridization events are considerably less prevalent than observed in pairings of domesticated species with their wild counterparts. In a recent scientific investigation, scholars affiliated with the American Museum of Natural History, the Smithsonian’s National Museum of Natural History, and the University of California, Davis, deployed sophisticated local ancestry inference techniques alongside phylogenomic assessments. Their comprehensive analysis scrutinized the genomes of 2,693 ancient and contemporary dogs and wolves. The results revealed that a substantial portion, precisely 64.1%, of modern domestic dog breeds harbor genetic contributions from wolves within their nuclear genomes. This admixture traces back to genetic exchange that occurred approximately a thousand generations in the past. Furthermore, every free-ranging dog genome examined demonstrated the presence of some ancient wolf DNA.
German Shepherd puppy. Image credit: Marilyn Peddle / CC BY 2.0.
“Contemporary canines, particularly those kept as pets, might seem vastly dissimilar to wolves, which are often viewed negatively,” commented Dr. Audrey Lin, a postdoctoral researcher at the American Museum of Natural History.
“However, certain traits, potentially inherited from wolves, are highly esteemed in today’s dogs, and we actively preserve them within their genetic lineage.”
“Although this research centers on dogs, it also offers significant insights into the nature of wolves.”
The evolutionary trajectory of dogs began with an extinct lineage of gray wolves, shaped by human intervention during the Late Pleistocene epoch, approximately 20,000 years ago.
Despite sharing geographical territories and the capacity for producing fertile progeny, direct interbreeding between wolves and dogs is uncommon.
Beyond a limited number of deliberate wolf-dog crosses, concrete evidence of gene flow between these groups has been scarce since the domestication of dogs led to the divergence of their respective gene pools.
“Prior to this investigation, prevailing scientific understanding suggested that a substantial presence of wolf DNA, if any, would preclude a creature from being classified as a dog,” stated Dr. Lin.
“Yet, our findings indicate that upon meticulous examination of modern canine genomes, wolf genetic material is indeed present.”
“This observation implies that dog genomes possess a degree of tolerance for wolf DNA, up to an unspecified threshold, while retaining their familiar characteristics.”
To elucidate historical patterns of gene exchange between dogs and wolves, the researchers analyzed 2,693 publicly available genomes. These datasets, sourced from the National Center for Biotechnology Information and the European Nucleotide Archive, encompassed wolves, domesticated dog breeds, village dogs, and other canids, with genetic material spanning from the Late Pleistocene to the present era.
The study determined that 64.1% of pedigreed dogs exhibit wolf lineage within their nuclear DNA, a consequence of genetic mixing that occurred roughly 1,000 generations ago.
Moreover, all examined genomes from village dogs—canines that live freely in or around human habitations—contained detectable ancestral wolf DNA.
Specific breeds developed through intentional wolf-dog hybridization, such as the Czechoslovakian and Saarloos wolfdogs, displayed the most pronounced wolf ancestry, accounting for 23-40% of their genetic makeup.
Among recognized dog breeds, the great Anglo-French tricolour hound exhibited the highest degree of wolf ancestry, ranging from 4.7% to 5.7%, followed by the Shiloh shepherd at 2.7% wolf DNA.
While the Shiloh shepherd’s development involved breeding with wolfdogs or recent dog-wolf hybrids to cultivate healthier, more companionable shepherd-type dogs in the United States, the origins of the significant wolf ancestry in the Great Anglo-French tricolour hound—the most prevalent hound breed in contemporary France—remain enigmatic and unexpected.
The Tamaskan, a breed characterized by its wolf-like appearance that originated in the United Kingdom during the 1980s through the selective breeding of huskies, malamutes, and other breeds with the aim of achieving a wolf-like aesthetic, possesses approximately 3.7% wolf DNA.
The scientific team identified several recurring patterns within the data: wolf ancestry was more prevalent in larger dog breeds and in those selectively bred for specific working roles, including Arctic sled dogs, ‘pariah’ dog types, and breeds used for hunting.
Conversely, terriers, gundogs, and scent hounds generally showed the lowest levels of wolf ancestry.
Although some large guardian breeds exhibit elevated wolf ancestry, others, such as the Neapolitan mastiff, bullmastiff, and St. Bernard, showed no discernible wolf genetic contribution.
Wolf ancestry is also present in a diverse array of dog breeds beyond these identified correlations, including the diminutive chihuahua, which carries approximately 0.2% wolf DNA.
“This finding resonates perfectly with anyone familiar with a chihuahua,” remarked Dr. Lin.
“What we’ve discovered is that this is the norm—most dogs possess a degree of wolf heritage.”
The researchers also conducted a comparative analysis, correlating terms used by kennel clubs to describe breed temperaments with the levels of wolf ancestry identified.
The descriptor most strongly associated with breeds exhibiting low wolf ancestry was ‘friendly,’ followed by ‘eager to please,’ ‘easy to train,’ ‘courageous,’ ‘lively,’ and ‘affectionate.’
In contrast, dogs with high wolf ancestry were more frequently characterized as ‘suspicious of strangers,’ alongside traits like ‘independent,’ ‘dignified,’ ‘alert,’ ‘loyal,’ ‘reserved,’ and ‘territorial.’
Other descriptive terms, such as ‘intelligent,’ ‘obedient,’ ‘good with children,’ ‘dedicated,’ ‘calm,’ and ‘cheerful,’ appeared with comparable frequency across both groups of dogs.
The research team emphasized that these characterizations represent subjective assessments of breed behaviors and cautioned that it remains unconfirmed whether specific wolf genes are directly accountable for these traits. Nevertheless, this discovery opens avenues for future investigations into canine behavioral science.
Furthermore, the scientists identified significant adaptive traits that dogs have acquired through their wolf ancestry. These include enhanced wolf ancestry in olfactory receptor genes among village dogs, whose survival depends on their ability to locate human food waste. Another notable finding is the prevalence of a gene akin to that found in Tibetan wolves, which aids Tibetan mastiffs in tolerating the low-oxygen environments of the Tibetan Plateau and the Himalayas.
“Dogs are our companions, but it appears wolves have played a substantial role in shaping them into the devoted partners we recognize today,” stated Dr. Logan Kistler, a researcher at the National Museum of Natural History.
“Throughout history, dogs have faced and overcome numerous evolutionary challenges inherent to living alongside humans. This includes adapting to high altitudes, foraging for sustenance in their free-ranging lives, or providing herd protection. It seems they have harnessed wolf genes as part of a versatile toolkit to ensure their ongoing evolutionary success.”
These groundbreaking findings were disseminated this week in the esteemed journal Proceedings of the National Academy of Sciences.
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Audrey T. Lin et al. 2025. A legacy of genetic entanglement with wolves shapes modern dogs. PNAS 122 (48): e2421768122; doi: 10.1073/pnas.2421768122
