The Evolution of Sled-Dogs
Was it artificial or natural selection?
Posted July 24, 2020
How did sled-dogs evolve?
In a recent June issue of one of the two most prestigious scientific journals, (i.e. Science,) a group of 35 researchers published an article arguing that "Arctic-adapted dogs emerged at the Pleistocene–Holocene transition"—thus moving the hypothesized origin of sled dogs from approximately 2,000 years ago back to at least 9,500 years. This is an enormous finding resting on a number of excavations in Siberia.
Mikkel-Holger S. Sinding, who is now a post-doc at the Trinity College Dublin, is the lead author of this study. He wrote in his "Behind the paper" article on Nature:
"In the vast and cold East Siberian Sea, raises an island only 30 sq. miles, hidden away from most of the world and in some sense hidden in time. Undisturbed, frozen and preserved. Here, archaeological excavation found a great Mesolithic settlement, where unique preservation gave unprecedented detail to an ancient way of life—people here had obsidian tools from 1,500 km away, they hunted reindeer and polar bear, they had the first sledges ever found, and vastly more dogs than any earlier site have ever documented."
These results challenged received wisdom among scientists. That humans and dogs shared a close and important relationship for survival in these regions is now uncontested:
You can easily imagine people using the many dogs and sledges to travel long distance travel for trade, hunting and transportation of resources, which makes these dogs the first “practical” sled dogs. This brings the intriguing question—how are these dogs related to modern dogs? And that was the main question of our study. We generated the pale-genome of a 9,500-year-old dog from the Zhokhov site and the jaw-dropping finding was that compared to other dogs and wolves, the majority of Zhokhov dog ancestry is more closely related to modern sled dogs, moving the establishment of the modern sled dog genealogy from an assumed 2,000 years ago to beyond 9,500 years.
Zhokhov Island was connected to the mainland 9,500 years ago and appears to have served as a processing center for reindeer and polar bear carcasses. Occupants of the village are believed to have used dog sleds to hunt and haul them. Some paleo-archaeologists have argued that the dogs were being bred by humans in or near the settlement while others have suggested that the humans were selecting dogs from a larger group that matched their desire, for example, for strong, big dogs to haul heavy loads or smaller, quicker ones to bay and harass bears while the human hunter killed it. — Mark Derr
Distinguishing whether humans actively selected for particular traits or whether surviving dogs simply were better adapted to their environment is here no easy task. Because of the harsh climate, it is likely that there was nothing resembling an "active breeding program." Life in these regions is brutal and short — with both humans and dogs simply undergoing evolutionary change due to a blind environmental filtration. Dogs that were not adept to their "sled-pulling lives" might simply have died on the way from one location to the next. No active interference (artificial selection) from humans may have been necessary to advance the eventual adaptions of sled-dogs. Similar to polar bears, sled-dogs received advantageous mutations that allowed them to live on a fat-rich diet without the associated health risks. This is unlikely to have been selected for by humans.
Human culture in the Artic like-wise co-evolved. As Sinding et al. argue: "dog sledding would have been highly advantageous—if not necessary" for the lives of Arctic human populations. It is, therefore, unfortunate that the modern availability of snowmobiles pushes them as Mark points out to extinction (see also here).
Sinding, M. H. S., Gopalakrishnan, S., Ramos-Madrigal, J., de Manuel, M., Pitulko, V. V., Kuderna, L., ... & Castruita, J. A. S. (2020). Arctic-adapted dogs emerged at the Pleistocene–Holocene transition. Science, 368(6498), 1495-1499.
Sonne, C., Langebæk, R., Dietz, R., Andersen-Ranberg, E., Houser, G., Hansen, A. J., ... & Meldgaard, M. (2018). Greenland sled dogs at risk of extinction. Science, 360(6393), 1080-1080. Chicago