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Since their emergence over 200,000 years ago, modern humans have established homes and communities all over the planet.
But they didn't do it alone.
Whatever corner of the globe you find homo sapiens in today, you're likely to find another species nearby: canis lupus familiaris.
Whether they're herding, hunting, sledding, or slouching, the sheer variety of domestic dogs is staggering.
But what makes the story of man's best friend so surprising is that they all evolved from a creature often seen as one of our oldest rivals: canis lupus, or the gray wolf.
When our Paleolithic ancestors first settled Eurasia roughly 100,000 years ago, wolves were one of their main rivals at the top of the food chain.
Able to exert over 300 lbs. of pressure in one bone-crushing bite and sniff out prey more than a mile away, these formidable predators didn't have much competition.
Much like human hunter-gatherers, they lived and hunted in complex social groups consisting of a few nuclear families, and used their social skills to cooperatively take down larger creatures.
Using these group tactics, they operated as effective persistence hunters, relying not on outrunning their prey, but pursuing it to the point of exhaustion.
But when pitted against the similar strengths of their invasive new neighbors, wolves found themselves at a crossroads.
For most packs, these burgeoning bipeds represented a serious threat to their territory.
But for some wolves, especially those without a pack, human camps offered new opportunities.
Wolves that showed less aggression towards humans could come closer to their encampments, feeding on leftovers.
And as these more docile scavengers outlasted their aggressive brethren, their genetic traits were passed on, gradually breeding tamer wolves in areas near human populations.
Over time humans found a multitude of uses for these docile wolves.
They helped to track and hunt prey, and might have served as sentinels to guard camps and warn of approaching enemies.
Their similar social structure made it easy to integrate with human families and learn to understand their commands.
Eventually they moved from the fringes of our communities into our homes, becoming humanity's first domesticated animal.
The earliest of these Proto-Dogs or Wolf-Dogs, seem to have appeared around 33,000 years ago, and would not have looked all that different from their wild cousins.
They were primarily distinguished by their smaller size and a shorter snout full of comparatively smaller teeth.
But as human cultures and occupations became more diverse and specialized, so did our friends: short stocky dogs to herd livestock by nipping their heels; elongated dogs to flush badgers and foxes out of burrows; thin and sleek dogs for racing; and large, muscular dogs for guard duty.
With the emergence of kennel clubs and dog shows during England's Victorian era, these dog types were standardized into breeds, with many new ones bred purely for appearance.
Sadly, while all dog breeds are the product of artificial selection, some are healthier than others.
Many of these aesthetic characteristics come with congenital health problems, such as difficulty breathing or being prone to spinal injuries.
Humanity's longest experiment in controlled evolution has had other side effects as well.
Generations of selection for tameness have favored more juvenile and submissive traits that were pleasing to humans.
This phenomenon of selecting traits associated with youth is known as neoteny, and can be seen in many domestic animals.
Thousands of years of co-evolution may even have bonded us chemically.
Not only can canines understand our emotions and body language, but when dogs and humans interact, both our bodies release oxytocin, a hormone commonly associated with feelings of love and protectiveness.
It might be difficult to fathom how every Pomeranian, Chihuahua, and Poodle are descended from fierce wolves.
But the diversity of breeds today is the result of a relationship that precedes cities, agriculture, and even the disappearance of our Neanderthal cousins.
And it's heartening to know that given enough time, even our most dangerous rivals can become our fiercest friends.
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A brief history of dogs - David Ian Howe

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shuting1215 2019 年 5 月 6 日 に公開
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