A genetic analysis published Nov. 24 found that most modern dog breeds carry small amounts of wolf ancestry from interbreeding in the past few thousand years.

The study, based on 2,700 genomes that included 1,872 dogs, indicates recent wolf DNA is present across much of the domestic dog population and has contributed to physical and behavioral traits, researchers said. Around 64% of modern dog breeds carry some wolf ancestry from this interbreeding, highlighting its significance in shaping various characteristics of our canine companions. The findings come from teams at the Smithsonian National Museum of Natural History and the American Museum of Natural History.

Scientists examined genomes from breed dogs, village dogs and wolves and traced stretches of wolf DNA that appear to have introgressed into dog populations well after the initial domestication of dogs. Among the breeds singled out in the analysis, the Chihuahua carried about 0.2% of its genome traceable to wolves, while Czechoslovakian and Saarloos wolfdogs showed the highest degrees of wolf ancestry. Researchers noted that interbreeding of dogs and wolves results in a range of traits, such as a greater tolerance or attraction to humans, illustrating how deeply intertwined their development has been.

“Dogs are our buddies, but apparently wolves have been a big part of shaping them into the companions we know and love today,” said Logan Kistler, curator of archaeobotany and archaeogenomics at the Smithsonian National Museum of Natural History.

Researchers said the wolf segments are not uniformly distributed across breeds and often fall in genomic regions tied to particular functions. The team reported that the stretches of wolf DNA found in village dog genomes contained genes related to olfactory receptors, suggesting an influence on scent-related abilities. The analysis indicates that enhanced olfactory abilities, such as enriched wolf genes at olfactory receptor loci, are among the common traits observed in dogs linked to wolf ancestry. How does the interbreeding of dogs and wolves affect dog behavior and temperament?

Behavioral tendencies also showed patterns linked to varying levels of wolf ancestry. Breeds with lower wolf ancestry were frequently described as “friendly,” “easy to train” or “lively,” while breeds with more wolf DNA were pegged as “suspicious of strangers,” “independent” and “dignified.” This behavioral differentiation reflects how the presence of wolf DNA may affect dog social dynamics, making them less cohesive and more cautious in unfamiliar situations compared to their wild counterparts.

“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,” said Audrey Lin, an evolutionary biologist at the American Museum of Natural History. “This completely makes sense to anyone who owns a Chihuahua.”

The research places these introgression events in the recent past — within the past few thousand years — rather than during the earlier domestication period tens of thousands of years ago. That timing implies repeated contacts between local dog populations and wild wolves after dogs had already become distinct from their wolf ancestors.

Analysts compared results across many breeds to map where wolf ancestry persists at low levels in typical companion and working dogs, and at much higher levels in breeds intentionally crossed with wolves or formed with recent wolf admixture. The Czechoslovakian and Saarloos wolfdogs, for example, retained the greatest proportions of wolf-derived DNA among the sampled breeds. What are some common traits that can be influenced by wolf ancestry in dogs?

Researchers emphasized that the presence of wolf DNA does not erase the distinctiveness of modern dogs but instead shows how genomes have continued to mix and shape traits over time. The genes identified in wolf-derived segments appear to have influenced body size, scent abilities and certain behavioral tendencies in ways the authors say are consistent with both natural and human-directed selection. For instance, traits like larger body size and even high-altitude oxygen tolerance have been noted in some modern breeds as a result of these genetic influences. What percentage of modern dog breeds are estimated to have wolf DNA?

The study’s authors include scientists affiliated with the Smithsonian National Museum of Natural History in Washington, D.C., and the American Museum of Natural History. Coverage of the findings has appeared in outlets including Live Science and ScienceDaily, which summarize the genetic analysis and its implications for traits such as scent and temperament.

By showing that wolf ancestry post-dates domestication and remains detectable across many breeds, the study reframes how scientists think about dog evolution as an ongoing process shaped by episodic contact with wild relatives.

Where this line of research goes next, the authors say, is toward mapping specific gene functions in more dog populations and clarifying how small amounts of wolf DNA translate into measurable traits in modern breeds.

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