New study reveals the hidden wild side of modern dogs
From giant shepherds to tiny chihuahuas, most modern dogs carry a hidden genetic connection to their wild ancestors.
According to new research led by scientists at the American Museum of Natural History and the Smithsonian’s National Museum of Natural History, the majority of dogs living today have small but detectable amounts of wolf ancestry in their DNA.
These ancient genetic traces may influence dogs’ body size, sense of smell, and even their personalities.
The study, published in the journal Proceedings of the National Academy of Sciences, challenges the long-held belief that dogs and wolves have been completely separated since domestication.
Instead, it shows that even after dogs became companions to humans thousands of years ago, there were still occasional genetic exchanges between dogs and wolves.
“Modern dogs, especially pet dogs, can seem so far removed from wolves,” said lead author Audrey Lin, a researcher at the American Museum of Natural History.
“But when we look closely at their genes, we see that wolves are still there. In many ways, this study is just as much about wolves as it is about dogs.”
Dogs are believed to have evolved from an extinct population of gray wolves around 20,000 years ago, during the late Ice Age.
Over time, they adapted to living alongside humans and developed into the wide range of breeds we see today.
While dogs and wolves can still mate and produce offspring, scientists had assumed that this almost never happened after dogs were domesticated.
To test this idea, the research team analyzed more than 2,700 genomes from wolves, purebred dogs, village dogs, and other related animals.
These genomes came from samples collected over thousands of years, from the late Ice Age to the present. The results were surprising.
Nearly two-thirds of modern dog breeds showed signs of wolf ancestry from cross-breeding that occurred roughly 1,000 generations ago. All village dogs, which live freely around human communities, also carried wolf DNA.
Some breeds that were intentionally mixed with wolves, such as the Czechoslovakian and Saarloos wolfdogs, had the highest amount of wolf ancestry, ranging from 23 to 40 percent. Among regular purebred dogs, the Great Anglo-French tricolor hound had the most wolf DNA, at around 5 percent. The Shiloh shepherd also showed elevated levels.
More unexpectedly, even the tiny chihuahua was found to have around 0.2 percent wolf ancestry. “This probably makes complete sense to anyone who has owned a chihuahua,” Lin joked. “What we found is that most dogs are a little bit ‘wolfy.’”
The study also explored how this hidden ancestry might influence behavior. Breeds with low wolf ancestry were more often described using words like “friendly,” “affectionate,” and “eager to please.”
In contrast, breeds with higher wolf ancestry were more likely to be called “reserved,” “independent,” “territorial,” or “suspicious of strangers.” While these personality descriptions come from kennel clubs and may involve some human bias, they hint that wolf genes could influence temperament.
Beyond behavior, wolf genes may have helped dogs survive in different environments. For example, village dogs had more wolf DNA in genes related to smell, which may improve their ability to find food. Tibetan mastiffs were found to carry a gene originally from wolves that helps them survive in low-oxygen, high-altitude environments in the Himalayas.
According to co-author Logan Kistler, this shows how dogs may have relied on their wolf relatives for important survival tools over time.
“Dogs live in very different conditions around the world. Whether they are guarding animals, roaming villages, or living in the mountains, it seems they have used wolf genes as part of their toolkit to adapt and thrive,” he said.
This research reveals that the line between dog and wolf is not as clear as once believed. Even today’s cuddly household pets still carry echoes of their wild past—proof that evolution continues to shape dogs in surprising ways.
