Short answers, pulled from the story.
Dogs were the first species to be domesticated, over 14,000 years ago, before the development of agriculture. Genetic studies suggest the domestication process may have begun over 25,000 years ago, with a 2021 review placing it in Siberia around 23,000 years ago.
The earliest remains conclusively identified as a domesticated dog were found at Bonn-Oberkassel, Germany, dated to 14,223 years ago. The dog was buried alongside a man and a woman, all sprayed with red hematite powder, and had survived canine distemper as a puppy.
There are around 450 official dog breeds, the most of any mammal. Most breeds descend from small numbers of founders within the last 200 years, and dogs began diversifying in the Victorian era when humans took control of their natural selection.
Dogs have roughly forty times more smell-sensitive receptors than humans, ranging from about 125 million to nearly 300 million in breeds such as bloodhounds. Smell is the most prominent sense of the species, while the dog brain is dominated by a large olfactory cortex.
A Border Collie named Chaser learned the names of over 1,000 words, and another named Rico knew the labels of over 200 items and inferred new names by exclusion learning. Dogs have about twice the neurons in their cerebral cortexes as cats, suggesting roughly twice the intelligence.
The estimated global dog population in 2020 ran between 700 million and 1 billion, making the dog the most widely abundant large carnivoran in the human environment. Only about 20 percent live in developed countries, while around three-quarters live as feral, village, or community dogs.
Dogs earned the nickname man's best friend because of their long association with humans and their influence on human society. They perform many roles including hunting, herding, protection, companionship, therapy, and assisting police, the military, and people with disabilities.