Though traces of the practice of sledding date more than 6,000 years ago, the Inuit tribes tamed wolves and built sleighs out of whalebone to move around the year 1000. Sled dogs are all descended from wolves, from which they retain essential features for such practice. They live in packs organized through social hierarchy and are hardy and resistant to cold. A quick team usually has eight to twelve dogs, while a more peaceful ride requires four.