Dogs and humans. We’ve been together a long, long time. In fact, some scientists say we’ve been hanging around with each other for over 15,000 years. Now that’s a real friendship!

When you look at all the different dog breeds, especially the huge variation in size, from a tiny Chihuahua to a towering Great Dane, it’s hard to believe they are the same species. But all dogs have a common history.

Dogs are members of the biological family Canidae, which is why they are also called canines. The canids are a subset of a bigger group known as Carnivora. According to the fossil record, the canids peeled away from this larger group some 40 million years ago.

Beginning about 15 million years ago, it appears they then divided into three subgroups: animals that were wolf-like, animals that were fox-like and another group known as the South American canids which includes such animals as the crab-eating fox and the maned wolf. The wolf-like group includes wolves of course, but also jackals and coyotes who are all related.

Some scientists, like Charles Darwin, who observed the staggering variety of dog shapes and sizes, thought that different modern dog breeds may have descended from different groups of wild canids. DNA analysis paints a different picture however. All modern dogs are descended from just one group…the wolves.

But scientists are not at all clear about how this descent happened and there are a lot of conflicting theories around but one of the most interesting goes like this: people had contact with wolves who hung around their villages looking for food. Naturally the “tamer” wolves became more accepted and apt to get food, while the more wary ones did not.

Gradually this village pressure on wolves to be tamer selected for those wolves whose genetic makeup reflected just that. But linked to the genes for more tameness and socialness were genes that affected the wolves’ appearance in terms of coat color and who were smaller. 

But here’s the most interesting idea of all. One theory says that some wolves gradually became dogs because of their long association with humans. But this new idea (that natural selection pushed wolves into evolving into dogs) means that dogs are their own animal…and were not just “created” by people. This statement from How Stuff Works sums it up perfectly

“Dogs…are truly their own species, shaped by the same process that created coyotes and other canids that have split from each other on the family tree. Perhaps by viewing dogs as deformed or substandard wolves created by people, we fundamentally misunderstand and underestimate them as the unique species that they are.”

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