Dogs and humans have been found to co-exist since more than 25,000 years ago, long before agricultural societies developed. Dogsledding has been a prerequisite for transport in polar environments and still is in rural communities in Alaska, Northern Canada and Greenland and for modern day survey operations in northeastern Greenland. The dogs represents an important part of the culture that probably dates back to when indigenous populations in present day Siberia started using dog sledges ca. 3000 years ago. Humans and their dogs formed a team where both depended on each other.
Dogs have been bred for the ability of pulling sledges by selecting for traits as strength and the desire to run for long distances. Interestingly, sled dogs maintain the most original wolf traits compared to other dog breeds. It also seems that dog domestication occurred earlier in hunter-gatherer societies (like the ancient dog sled cultures in Siberia) than in the agricultural societies. This is based on the finding of a high copy number of the amylase gene in all domesticated dog breeds, except for the Husky and Dingo as well as the wolf. The increase in copy number of the amylase gene is thought to have occurred when agricultural societies spread and dogs adapted with an increased ability to digest agricultural waste rich in starch.
Sled dog behavior consists of a strong hierarchy and pack structure similar to wolf, which is useful when human and dogs are relying on each other in the wilderness. The ability to pick up the scent of predators and prey are crucial for survival. Still today, dogs are considered more reliable than more modern alternatives for transport in remote polar areas. An example being that military surveys are carried out by dog sledding in North East Greenland during winter, as the risk of running out of fuel or having breakdowns is too great a risk in such remote areas. Here dogs are much more reliable and the best method for transport.
More information on the subject can be found in the references below:
Genome Sequencing Highlights the Dynamic Early History of Dogs.
Freedman AH, Gronau I, Schweizer RM, Ortega-Del Vecchyo D, Han E, et al. (2014) Genome Sequencing Highlights the Dynamic Early History of Dogs. PLoS Genet 10(1): e1004016. doi: 10.1371/journal.pgen.1004016.