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Dogs have long been considered man’s best friend, and with good reason. Over the centuries, our four-legged four-legged companions have developed into loyal partners.
A growing body of scientific research suggests that our furry friends have distinctive traits and abilities that enable them to perceive, understand, communicate, and show affection for people.
From sniffing when we’re stressed to tearing up when we reunite with their owners, here’s what science reveals about how humans’ special relationship with dogs has evolved over time.
Scientists generally agree that dogs evolved from wolves about 15,000 years ago into the furry, retrieving pets they are today. However, scientists have different theories about how exactly the separation of wolves took place.
In a study published in June in the journal Nature, geneticists at the Francis Crick Institute analyzed the genomes — or the entire genetic information — of 72 ancient wolves from Europe, Siberia and North America over a 100,000-year period. Then they compared the wolf DNA that makes up the genome with the DNA of modern and ancient dogs.
By analyzing DNA, scientists found that early and modern dogs most closely resemble gray wolves in Siberia around 13,000 to 23,000 years ago, suggesting domestication occurred somewhere in Asia.
“This is consistent with a Central Asian wolf population leading to the emergence of dogs,” Adam Boyko, a canine geneticist at Cornell University who was not involved in the study, previously told Insider.
That might not be the end of the story, Boyko added. The results do not rule out the possibility that dogs were domesticated multiple times, as ancient dogs in the Middle East, Africa, and southern Europe also show ancestry from wolves in the Middle East.
Though their wild ancestors are known for their fierce nature, dogs have evolved over time to have larger and more baby-like eyes.
In a 2019 study published in the Proceedings of the National Academy of Science, researchers discovered that dogs have muscles around their eyes that help them do dog eyes — that soft, cross-eyed look that melts your heart . Wolves don’t have these muscles, suggesting that dogs’ adorable expressions are an evolutionary trait that helped them get along better with humans.
Dogs may be able to smell when they’re stressed, according to a study published in September in Plos One. Stress responses trigger physiological changes in humans’ sweat and breath that dogs can detect.
The study involved collecting breath and sweat samples from human participants before and after completing a “stress-inducing” task. Then, dogs trained to recognize smells had to choose between a sample from an unstressed and a stressed person. The dogs correctly identified the stress test 94% of the time.
“This study shows that dogs can distinguish between breath and sweat taken from humans before and after a stress-inducing task,” the study authors wrote, meaning they were able to identify human odors associated with stress.
Dogs even take on their owners’ personalities. A 2019 study published in the Journal of Research in Personality surveyed more than 1,600 dog owners from about 50 different breeds. Owners were asked to rate their dogs’ personalities and answer questions about their dogs’ behavioral histories. The owners were also asked questions about their own personality.
Extroverted owners rated their dogs as more active and playful, while owners of more anxious dogs reported more negative emotions.
And while several studies support the notion that dogs and owners often look alike, that’s mainly because owners tend to choose dog breeds based on the breed’s similarity to themselves.
Research suggests that dogs are hardwired to communicate with and understand humans in unique ways.
“Dogs are very responsive to how we talk to them,” John Bradshaw, an anthropologist and author of The Animals Among Us, previously told Insider. “It fools a lot of owners into thinking they literally understand every word.”
But while they may not understand the words you’re saying, Bradshaw added, dogs are very good at learning to respond to their owner’s tone of voice in certain ways. “It’s almost true that the dog will respond to every word they say,” Bradshaw said.
A 2021 study published in the journal Scientific Reports found that dogs can tell the difference between people’s accidental and intentional actions — or, in other words, when we make mistakes.
The experiment involved 51 dogs who were taught that they would get treats from a human through a gap in a glass partition. Then the researchers looked at how dogs reacted when they were denied food rewards.
In the study, dogs waited much longer to retrieve the treat when the researcher intentionally withheld it than when the researcher dropped it or couldn’t get it through the glass partition. This finding suggests that dogs can distinguish between intentional and unintentional human actions.
“Dogs’ communication skills uniquely position them to fill the niche they occupy alongside humans,” Emily Bray, a canine cognition researcher at the University of Arizona, Tucson, previously told Insider in an email. “Many of the tasks they do for us today and in the past (e.g. herding, hunting, tracking, service dogs) are facilitated by their ability to understand our cues.”
Dog happy to see owner.
Madoka Nakamura
It’s common to see dogs overjoyed to be reunited with their owners.
In a study published in Current Biology in August, researchers recruited 22 dogs and their owners. First, the researchers measured the tear volume in the eyes of dogs during a normal interaction with their owners as a baseline. Then, after they were five to seven hours away from their owner, the researchers measured the tear volume on the surface of the dogs’ eyes each time they were reunited.
