It may be hard to believe, but all dogs, even Chihuahuas, are descended from wolves.
Their ancient ancestors are long extinct, and the closest living relative to today's dog is the gray wolf - a powerful predator that still roams the wild today.
But when exactly did wolves start living near us, and why do so many people around the world love dogs?
How did we get to the dogs we have today?
Dogs are believed to be the first animals domesticated by humans.
Researching ancient dog DNA conducted in 2017 found that they most likely evolved from wolves in just one place in Europe, 20.000 to 40.000 years ago.
It was previously believed that dogs were domesticated from two wolf populations that were thousands of kilometers apart.
But the story of how the first dogs actually became domesticated descendants of wolves is still being researched.
Exists many theories.
For example, one popular theory suggests that humans domesticated wolves by capturing and raising pups, then over generations breeding with individuals that were less aggressive to help them hunt.
According to another well-known theory, wolves practically domesticated themselves.
The wolves that were least afraid approached human settlements in search of food, and at some point people realized that this relationship could be beneficial to them.
Braver wolves had a better chance of surviving and reproducing, and these "tame" traits were passed down through generations due to natural selection.
Watch the video: A scientific explanation of people's love for dogs
Greger Larson, a geneticist and professor of genomics at the University of Oxford, believes it was a coincidence, the moment we realized we could help each other.
"If we say that we domesticated wolves, it implies a certain intention that most relationships in our lives simply do not have."
"And so it sounds like we knew what we were doing, that we had a plan and were smart about it," explains Professor Larson.
He says that at the beginning of the relationship there were mutual benefits, such as more effective hunting.
"I think we probably benefited, because if those wolves saw us as one of their own, they acted like guards, which made everything a little safer."
"And for wolves, that could have meant a more regular source of food," he adds.
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Over thousands of years, people began to selectively breed dogs for certain traits for specific needs, such as hunting and herding.
And their capabilities and applications have changed drastically from the days when they were just guarding caves.
Today, they have numerous roles - from guides for the visually impaired, searchers in rescue services to sniffers of suspicious packages at airports.
This human influence on natural selection is the reason why there are hundreds of different dog breeds today.
Dogs also have a greater range of sizes than any other mammal, points out John Bradshaw, who studies human-animal interactions.
At some point, the dog's role changed from a mere helper to a family member.
Analysis of tombstones in public pet cemeteries in the United Kingdom (UK), conducted by Newcastle University in 2020, revealed major changes in our relationship with pets since 1881, when the first such cemetery opened.
According to research, in the Victorian era (from 1837 to 1901), pets were more often described on tombstones as companions or friends, while later inscriptions show that they were considered by their owners family members.
It has also been noted that the number of inscriptions mentioning animals as family members increased after World War II.
The research also documented a growing belief in the afterlife of pets by mid-20th century.
Irresistibly sweet
It is ideal for puppies to stay with their mother and siblings for between eight and 12 weeks, according to the Cornell University College of Veterinary Medicine in the United States (US).
This is a crucial period for their socialization and development.
And a 2018 study by Arizona State University indicates that dogs are at their cutest around that age.
"It is during this crucial period, when puppies are most vulnerable, when they need their mother and when they are completely incapable of surviving on their own, that they are also the sweetest to humans, who are most likely to pick them up, take them home and start feeding them," says Professor Larson.
Also, a 2019 study showed that dogs have developed muscles around their eyes that allow them to make expressions that are particularly appealing to humans, like that famous "sad puppy dog look."
The study states that this is what helped domesticated dogs bond better with humans.
"Once a puppy learns that people are friendly towards it, its instincts tell it that its best chance for survival is to bond with a human," explains Bradshaw.
Most people are convinced that their dogs love them, and scientists now have evidence that it is attachment to humans that drives many of dogs' behaviors.
Gregory Burns, a neuroscientist and professor of psychology at Emory University in the US, studies the relationship between dogs and humans.
He trained dogs to sit still during functional magnetic resonance imaging (fMRI) so he could observe their brains.
His research found that the part of the brain associated with positive expectations is mostly activated when dogs smell a familiar human.
So, maybe we can't help but love them, but it seems the feeling is mutual.
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Bonus video:
