Why do dogs smile but wolves don't? This has to start with the evolution of dogs 30,000 years ago

Why do dogs smile at you but wolves don't? Many people may answer this: Because the wolf only thinks how to eat you. This is a witty answer that makes no sense. Don't look at a dog's smile so relaxed and comfortable, but behind it is a complex and long evolutionary history.

There is no doubt that dogs are man's best friend. In ancient times, dogs could help humans hunt and even fight. Nowadays, dogs are of great help to humans. They can guide the blind, search and rescue, and detect... In fact, for most people who treat dogs as pets, dogs can help them reduce stress and improve their health.

So the question is, why for thousands of years, only dogs are most likely to establish an intimate relationship with humans (cat: go away, Lao Tzu only regards you as a shit shovel officer)? One of the most plausible explanations in the scientific community is that dogs express emotions in a similar way to humans. If you've ever owned a dog, it's familiar to you, you can understand how a dog feels, and a dog will understand how you feel. Especially: when they are happy, they will smile at you.

Dogs are probably more attuned to human behavior and emotions than any other animal. Not only do dogs respond to human body language, gestures, and verbal commands, but they seem to understand the emotions we express. The ability of dogs to tune their emotions into humans may not be accidental: some scientists believe that this ability to express emotions in a human-like way can be explained by evolution.

Wolves are the ancestors of dogs, and dogs are descendants of wolves, but wolves and dogs are very different in behavior.

The biggest difference between dogs and wolves is that wolves will get rid of the "dumb" characteristics of their cubs and gradually become "fierce" when they become adults, but dogs can remain "dumb and cute" as adults. This feature is called "naive". Some naive traits of adult dogs include a wider skull and shorter snout than wolves, which combine to create a pup-like face. Also, dogs generally have floppy ears, and they also have shorter teeth and smaller jaws. All to make them look cuter.

Not only physical traits, but some naive traits are also manifested in dog behavior. For example, adult dogs wag their tails and show submissive behavior, which is common in wolf pups but not in adult wolves. That is to say, pups and wolves are cute and cute, but wolves discard these traits as adults, but dogs retain them as adults.

In the same way, childishness is also shown in the expressions of adult dogs. One study once looked at the inner eyebrows of dogs, which were created when the dog "raised the middle part of the eyebrows, increasing the apparent size of the eyes relative to the face." By increasing the size of the eyes relative to the face, this action makes the dog look more childish, since most animals' pups have relatively large eyes to face ratios, which makes them more adorable and caring.

Some scientists believe that dogs evolved to have these puppy-like traits because humans may have preferred them. In other words, evolution can help explain differences in behavior between dogs and wolves. Dogs were first differentiated from wolves more than 30,000 years ago, and later with the differentiation of genes, they were finally domesticated by humans. After domestication, dogs are further developed into different types and breeds. It is not known exactly when dogs were domesticated, but it must have been as early as 14,200 years ago, and possibly as early as 36,000 years ago. A major explanation for the evolutionary differences between wolves and dogs is that dogs co-evolved with humans because it benefits their evolutionary fitness. There are two explanations for the occurrence of this phenomenon: symbiotic evolution and co-evolution.

Symbiotic evolution

co-evolution

The theory of symbiotic evolution proposes an evolutionary pathway in which wolves can make better use of human habitats. For example, they might benefit from removing litter left by early humans, or prey on animals that were attracted to early humans' habitats, such as small rodents such as mice.

To maximize opportunities from human habitats, these animals may become less aggressive and docile. Eventually, over time, as humans and dogs developed a strong bond, humans began to domesticate dogs and then keep them as pets. Symbiotic evolution theory holds that dogs evolved by adapting to humans in a way that made it easier for dogs to survive, leading to the naive behavior we see in adult dogs today.

Another similar explanation focuses on how dogs and humans evolved together (ie, co-evolution). This theory puts more emphasis on how humans co-evolved with dogs. This idea begins with the observation that wolves have excellent cooperative behaviors, including cooperatively attacking prey, caring for each other's pups, and providing food for the pups and other pack members.

Wolves have adapted to follow the vast number of migratory animals in Eurasia. Humans evolved from tree-dwelling apes to field-running apes, and may eventually adopt a migratory lifestyle. At this point, humans became more omnivorous as they moved away from food sources previously obtained in the forest, became skilled hunters, and adopted a lifestyle similar to that of wolves, following migratory animals in the grasslands.

It was at this time that humans and wolves made their first contact: following herds of ungulates on the steppe. Wolves preying on cattle help keep the herd healthy because they take away the weakest and sick members of the herd. So humans may have adapted to some extent following wolves to keep healthy herds. It was at this point that humans and wolves became interdependent, in part because they shared similar cooperative behaviors, and eventually dogs separated from wolves to co-exist with humans.

While the two theories differ in how dogs and humans co-evolved, they both emphasize the importance of humans to dog evolution. Thus, they all offer similar explanations for the dog's naive facial expressions: These facial expressions may allow dogs to more successfully exploit resources from human habitats and ultimately survive and reproduce. Since naive traits and rich facial expressions suggest that dogs are docile, humans may prefer to let dogs with naive traits go for food. During the domestication stage, humans may be more inclined to choose dogs with these facial expressions as pets.

Both explanations have their own plausibility, but both fit a similar evolutionary explanation: Humans prefer this behavior. Since humans prefer these specific facial expression behaviors, humans may behave differently to dogs that show facial expressions so that they can breed more successfully. In this way, co-evolution with humans may be partly responsible for naive expression in dogs.

So when your dog smiles at you, you know what a complex and long evolutionary history dogs and humans have gone through.