Evidence suggests that dogs were first trained in East Asia, possibly China, and some of the peoples who entered North America took dogs with them from Asia.
Domestic dogs often display the remnants of counter-shading, a everyday natural camouflage pattern. The habitual theory of countershading is that an bestial that is lit from above will appear decrease on its upper divided and darker on its lower all where it will especially be in its own shade. This is a pattern that predators can learn to watch for. A countershaded animal will have dark coloring on its upper surfaces and light coloring below. This reduces the humdrum visibility of the animal. One reminder of this pattern is that many breeds will have the especial "blaze", stripe, or "star" of Dog Arthritis Treatment white fur on their chest or undersides.