Scientists say traces of wolf DNA can be found across nearly every modern dog, from Chihuahuas to huskies, indicating a persistent genetic overlap long after dogs were domesticated at least 20,000 years ago. The finding is based on genome analyses of 2,693 dogs and was published in the Proceedings of the National Academy of Sciences. Coverage from Nature has highlighted this story.

The study was led by Audrey Lin, postdoctoral researcher at the American Museum of Natural History, and included colleagues affiliated with the Smithsonian’s National Museum of Natural History and the University of California, Davis. Their work traces wolf-like ancestry to hybridization events occurring roughly a thousand generations after domestication and identifies additional interbreeding within the past two centuries.

The researchers reported a wide range of wolf ancestry across individual animals and breeds. Small companion dogs such as the Chihuahua retain about 0.2% wolf ancestry, while recognized wolfdog breeds show far higher levels: the Czechoslovakian wolfdog and the Saarloos wolfdog contain as much as 40% wolf DNA. The dataset also included a Greenland dog–Arctic Wolf halfbreed categorized as a dog-wolf hybrid. Reporting by Sciencedaily offers additional detail on this case.

Some genetic signatures highlighted functional inheritance in particular populations. The Tibetan mastiff, for example, carries a gene variant called EPAS1 that allows tolerance of low-oxygen conditions, a trait noted by the authors in their description of breed-specific ancestry.

“Modern dogs, especially pet dogs, can seem so removed from wolves, which are often demonized,” Audrey Lin said. She added that previous scientific views had assumed little or no wolf DNA in dogs: “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.”

Co-author Logan Kistler emphasized the long-term role of wolves in shaping dog genomes: “Dogs are our buddies, but apparently wolves have been a big part of shaping them into the companions we know and love today,” he said, placing those genetic traces in the context of the animals’ shared history with people. As covered by Pnas, readers can explore more context around the event.

The paper places these admixture signals well after the initial domestication event, arguing that wolf–dog interbreeding continued across time and geography. That timeline — domestication at least 20,000 years ago followed by hybridization roughly a thousand generations later and further interbreeding in the last two centuries — frames the persistence of wolf ancestry in modern animals sampled for the study.

The research group drew on published genomes to assemble the sample of 2,693 dogs and compared patterns of ancestry across breeds and village dogs. The authors report both low-level traces in many common breeds and concentrated wolf ancestry in particular types of dogs and recognized wolfdog crosses.

This work, published in PNAS, was discussed in institutional announcements and coverage summarizing the findings and their implications for how dog genomes retain elements of their wild relatives. Readers can find the peer-reviewed article in the Proceedings of the National Academy of Sciences and an institutional summary at ScienceDaily.

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Original reporting: view the original article.