Scientists discover hidden wolf DNA in most dogs

"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 American Museum of Natural History. "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."

Ancient Origins and Limited Hybridization

Dogs trace their origins to an extinct population of gray wolves that evolved alongside humans during the late Pleistocene about 20,000 years ago. Although wolves and dogs still share territory and are capable of producing fertile offspring, actual hybridization between them is unusual. Except for a few deliberate crosses, researchers have found little evidence of genetic mixing after domestication established separate lineages.

"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."

Large Genomic Survey Highlights Deep Ancestry Links

The research team examined more than 2,700 published genomes from the National Center for Biotechnology Information and the European Nucleotide Archive, including wolves, breed dogs, village dogs, and other canids from the late Pleistocene to the present. Their analysis revealed that almost two-thirds of breed dogs retain wolf ancestry within their nuclear genome from hybridization events that occurred around 1,000 generations ago. Every village dog genome studied also showed detectable wolf ancestry. Village dogs are free-roaming animals that live in or near human communities.

Czechoslovakian and Saarloos wolfdogs, intentionally bred through wolf-dog hybridization, had the highest wolf ancestry levels at 23-40 percent. Among typical dog breeds, the great Anglo-French tricolor hound had the strongest signal at 4.7 to 5.7 percent, followed by the Shiloh shepherd at 2.7 percent. While the Shiloh shepherd's wolf ancestry fits with its history of breeding with wolfdogs or other recent hybrids to create healthier shepherd dogs in the US, the elevated wolf ancestry in the Great Anglo-French tricolor hound, the most common hound in France, is both unexpected and unexplained. The Tamaskan, a "wolfalike" breed created in the UK during the 1980s by selecting huskies, malamutes, and other dogs for a wolf-like appearance, has about 3.7 percent wolf ancestry.

Wolf Influence Across Dog Types and Sizes

The researchers identified several broad trends in their data. Larger dogs and those bred for specific types of work, such as Arctic sled dogs, "pariah" breeds, and hunting dogs, tended to have higher levels of wolf ancestry. Terriers, gundogs, and scent hounds typically had the lowest levels. Some large guardian dogs showed high wolf ancestry, while others, including the Neapolitan mastiff, bullmastiff, and St. Bernard, showed none. Wolf ancestry also appeared in breeds that did not fit these patterns, including the chihuahua, which had 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."

Personality Traits and Wolf Ancestry Trends

The team also compared how kennel clubs describe the behaviors of breeds with the highest and lowest wolf ancestry. Breeds with low levels were most often labeled "friendly," followed by "eager to please," "easy to train," "courageous," "lively," and "affectionate." Breeds with higher wolf ancestry were more often described as "suspicious of strangers," "independent," "dignified," "alert," "loyal," "reserved," and "territorial." Descriptors such as "intelligent," "obedient," "good with children," "dedicated," "calm," and "cheerful" appeared with similar frequency in both groups. The researchers emphasized that these personality labels reflect human observations and that it remains unclear whether wolf-derived DNA directly influences these traits. Even so, the findings open new directions for future behavioral research.

Wolf-Derived Adaptations in Modern Dogs

The study also highlighted several adaptations that dogs appear to have inherited from wolves. Village dogs showed enriched wolf ancestry in olfactory receptor genes, which may support their need to locate human food waste. Another adaptation traced to a Tibetan wolf-like gene enables Tibetan mastiffs to tolerate low-oxygen environments in the Tibetan Plateau and the Himalayas.

"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 of archaeobotany and archaeogenomics 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, whether it's surviving at high altitude, searching for their next meal as they freely roam a village, or protecting the herd, and it seems like they use wolf genes as part of a toolkit to continue their evolutionary success story."

Other study authors include Regina Fairbanks, from the University of California, Davis; Jose Barba-Montoya, from the American Museum of Natural History; and Hsiao-Lei Liu, from the National Museum of Natural History and University of Stockholm.