The collar above, the first known Dog collar, dates back to about 4000 BC. Science tells us through mitochondrial DNA (the circular DNA chains passed on maternally within the mitochondria of your cells, not the standard DNA chain sequences) that the first five female dogs separated from the Silver Wolf genome about 100,000 years ago. Our first evidence of human interaction with them comes from Cave drawings.
That means that at the point we were just learning to use tools for writing and communicating images, Dogs were a regular part of Human life and evolution. Indeed, I remember reading an article in Archaeology Today, the paper mag version, that suggested that humans actually learned cooperative hunting techniques from wolves and canines, thus posing the question: what came first… Dogs or human civilization?
In every ancient society they are present, and are easily seen as domesticated by the collars. Note in the cast of the dog lost in the eruption of Mt Vesuvius, in 79 B.C., that destroyed Pompeii, a collar can easily be seen around the poor pups neck. I would imagine, sadly, that his owner was not far from him at the other end of that leash. As with the dog owners who died with their dogs in New Orleans during Katrina, it would seem Pompeii had similar dog owners who would rather die than leave their pet behind.
How and why Dogs and modern Humans spread so quickly across the globe remains a mystery. There is one thing that is completely clear… we did it together.