Dogs: Characteristics, Breeding Key Points and Frequently Asked Questions

Dog (scientific name: Canis lupus familiaris), commonly known as dog, also known as domestic dog, is a subspecies evolved from the gray wolf (Canis lupus lupus) after long-term domestication by late Homo sapiens. It is also the canine mammal with the largest population and the richest polymorphism in the world. Dogs are the earliest creatures domesticated by humans, during the Last Glacial Maximum about 26,000 to 19,700 years ago, before the Neolithic Revolution. Through tens of thousands of years of artificial selection, humans have developed hundreds of dog breeds (breeds) of different shapes according to different needs. For example, the height ranges from a Chihuahua with a height of only 15.2 cm (6.0 inches) to an Irish Wolfhound with a height of 76 cm (30 inches). The coat color also comes in various colors such as white, black, gray, yellow, brown, etc. Most of these dog breeds appeared in the past few hundred years. The lifespan of a dog can exceed twenty years at most, with the average lifespan being more than ten years, which is similar to the average lifespan of a cat. Barring accidents, small dogs live longer on average. Although wild gray wolves and many domestic dogs are very different in size, shape, and behavior, there is no real reproductive isolation between the two, and they can mate to produce fertile wolfdogs. DNA analysis shows that dogs are not only a subspecies of wolves, but also hybrid descendants of different wolf subspecies from various places. The ancestors of modern dogs diverged from the ancestors of today’s gray wolves in the late Pleistocene, about 20,000 to 40,000 years ago. After that, some groups gradually lowered their vigilance and hostility towards humans due to frequent contact with human tribes in their activity areas, and formed a mutually beneficial symbiotic relationship (for example, wolves can scavenge leftover food abandoned by humans, while humans can use the territorial awareness and alarm barking of wolves near camps to defend against intrusion by large predators such as cave lions and bears). Current research suggests that the earliest domestication of dogs began with the ancient Eurasians in Siberia, and then spread westward and southward to other parts of Eurasia. Earlier humans may have also tried to tame wolves into dogs, but these ancient dogs have become extinct. For example, specimens found in Belgium about 36,000 years ago and in the Altai Mountains about 33,000 years ago show that domestication events have been interrupted. These earlier ancient dogs did not leave any living descendants. A 2016 study showed that modern dogs were domesticated at least twice. About 14,000 years ago, a small number of domestic dogs that were domesticated in Asia followed humans eastward across the Bering Land Bridge and entered North America. Then, about 3,500 years ago, they entered the Australian continent with the cross-sea migration of the Austronesian peoples. After that, they became wild and became dingoes, which gradually spread across Australia and became the top predator. This means that all modern domestic dogs, as well as the Newgrange Tomb Dog, can trace their ancestry back to Asia. Genetic testing has revealed that many genotypes of Paleolithic European dogs are not found in modern European dogs.