Why do sled dogs pull?
Men have used dogs to pull things since thousands of years. This due to the fact that they were basically the only domesticated animal who could pull an object –like a sled for example. Many ancient civilizations have used them to draw loads, but the most well-known are the Alaskan tribes.
In Alaska for example the indigenous people started to breed different races of dog to get a breed that could pull in an instinctive way. After some trials they decided that the most important aspect was not only to pull, but how fast they go, how long a time could they perform this activity and if they could lead the group.
This is a completely different breed that doesn't stop to look for delicate features, but for strong sturdy ones. That's how we get current days "sled dogs."