Sled dogs have well-known roots in human prehistory. A 12,500-year-old tool found at an arctic site hints at its possible use on sleds. And archaeological surveys on a well-known site on the island of Zhokov in the Siberian Sea discovered dog bones and sled technology indicating that dogs may have been the first canids bred for a specific task.
Dr Sinding and his colleagues dug deeply into the DNA of one of these dogs, using a jawbone from the site dating to 9500 years ago. They also sequenced the genomes of a 33,000-year-old Siberian wolf and 10 modern Greenland sled dogs. They also relied on other canine genomes archived in databases.
They discovered that the Zhokov dog was closest to modern sled dogs, especially Greenland sled dogs, which are a “land breed,” bred for a task and sharing an appearance and demeanor, but not the kind. of breed for which the herd books and records are kept.
The Zhokov dog was not a direct ancestor of modern sled dogs, but he did share a common ancestor with modern sled dogs that was probably around 12,000 years old. This evidence suggests that the type of sled dog, bred to carry loads in severe winters, was established as early as 9,500 years ago.
The researchers also found that sled dogs, both ancient and modern, did not exhibit crossbreeding with wolves, although other modern dog breeds did, and that dog-wolf matings were known in Greenland to the historical period. The results suggest that the hybrids may not have been very useful for pulling sleds.
Next, researchers began to look for different genes in sled dogs from wolves and other dog breeds. They found several that made sense. One is involved in a variety of physiological functions, including calcium transport and temperature sensitivity. They don’t know exactly what this does in sled dogs, but they do know that several similar genes are different in mammoths, cold creatures and elephants, animals of more temperate climates, suggesting some sort of adaptation to arctic life.
Another gene that sets sled dogs apart from other dogs is involved in managing low oxygen conditions. It is also found in a group of humans, nomads of the sea, who have been diving for thousands of years. This could, Dr Sinding said, contribute to suitability for the extreme demands of long sleigh rides.