<P> In 2018, a study compared sequences of fossil North American dogs with fossil Siberian dogs and modern dogs . The study indicates that dogs entered North America from Siberia 4,500 years after humans did, were isolated for 9,000 years, and after contact with Europeans these no longer exist because they were replaced with Eurasian dogs . The pre-contact dogs exhibit a unique genetic signature that is also now gone, with their nearest genetic relatives being the arctic breed dogs . </P> <P> In 2017, a study showed that 9,000 YBP the domestic dog was present at what is now Zhokhov Island, arctic north - eastern Siberia, which was connected to the mainland at that time . The dogs were selectively bred as either sled dogs or as hunting dogs, which implies that a sled dog standard and a hunting dog standard existed at that time . The optimal maximum size for a sled dog is 20--25 kg based on thermo - regulation, and the ancient sled dogs were between 16--25 kg . The same standard has been found in the remains of sled dogs from this region 2,000 YBP and in the modern Siberian husky breed standard . Other dogs were more massive at 30 kg and appear to be dogs that had been crossed with wolves and used for polar bear hunting . At death, the heads of the dogs had been carefully separated from their bodies by humans, probably for ceremonial reasons . </P> <P> The study proposes that after having diverged from the common ancestor along with the grey wolf, the evolution of Canis familiaris proceeded in three stages . The first was natural selection based on feeding behavior within the ecological niche that had been formed through human activity . The second was artificial selection based on tamability . The third was directed selection based on forming breeds that possessed qualities to help with specific tasks within the human economy . The process commenced 40,000 - 30,000 YBP with its speed increasing with each stage until domestication became complete . </P>

Where did all the different dog breeds come from