Friday, June 18, 2021

Sled dogs did not descend from wolves

Greenland sled dogs, a fluffy, curly-tailed canine native to the harsh Arctic tundra, could be the oldest dog breed. The sled dog branch of the family tree, which includes various types of huskies and malamutes, broke off from the rest of the dogs around 9,500 years ago, versus something like a labradoodle, which only became a breed in 1989.

Scientists know that dogs likely evolved from Eurasian wolves, but exactly when or where that transformation took place is a matter of great mystery. To better understand the genetics of sled dogs and their place in the world, scientists sequenced the genome of a dog from Siberia’s Zhokhov archaeological site, dating to around 9,500 years ago.

They found today’s sled dogs and the Zhokhov dog descended from the same branch. That’s a huge finding because it provides the “first firm date for diversification in dogs”—in itself an important clue in the mystery of dog domestication.

The analysis, which compared genes between ancient and modern dog sled dogs with those of other breeds, also revealed all sorts of fascinating and unique adaptations to Arctic life, such as the ability to thrive on a high-fat diet.

One of the biggest differences between a brown bear and a polar bear is that the polar bear has a specific genetic adaptation for eating lots of blubber. And scientists saw almost precisely the same solution in [sled] dogs. This makes logical sense, as the Inuit and Thule peoples of the Arctic and their working dogs have survived for thousands of years by hunting blubber-rich marine mammals, like seals and whales.

The scientists also compared the Zhokhov dog’s DNA with an even more ancient canid — a Siberian Pleistocene wolf that lived about 33,000 years ago. Together with genomes from modern wolves and domesticated dogs, the team revealed that, remarkably, sled dogs haven’t interbred with gray wolves in the past 9,500 years, unlike other breeds. This is especially strange, given that indigenous peoples have documented dog-wolf pairings. The fact that traces of wolf genetics don’t show up in the Greenland sled dogs’ genome suggests that either hybrids didn’t survive well, or that there was some reason humans did not breed them.

The research also showed that sled dog genomes contain mutations related to their cold environments, such as running and pulling sleds in low-oxygen conditions. Another mutation allows sled dogs to highly regulate body temperatures.

Curiously, such traits are still present in today’s pooches, which provides useful guidance for pet owners — particularly those with purebreds.


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