As early as 7,400 years ago, Siberian dogs had evolved to be much smaller than wolves, making them more dependent on humans for food, including marine mammals and fish trapped under the ice, a new study showed Friday.
University of Alberta’s Robert Losey, who led the study published in Science Advances, said the findings helped explain the growth of early dog populations as people used them for hunting, herding and sledding.
“The long-term changes in dog diets have really been oversimplified,” he told AFP, explaining that work to date has focused on just two main ideas for explaining how dogs transitioned from wolves, a process that happened before started about 40,000 years ago.
The first of these was that during the Ice Age, friendlier wolves would approach human camps in search of meat, eventually becoming isolated from their wild counterparts, and then purposely bred into dogs.
The second was that some dogs evolved a better ability to digest starch after the Agricultural Revolution, which is why some modern dog breeds have more copies of the AMY2B gene, which makes pancreatic amylase.
To study the diets of ancient dogs more closely, Losey and colleagues analyzed the remains of about 200 ancient dogs dating back 11,000 years and a similar number of ancient wolves.
“We had to go to collections all over Siberia, we analyzed these bones, took samples of the collagen and analyzed the protein in labs,” he said.
Based on the remains, the team made statistical estimates for body sizes.
They also used a technique called stable isotope analysis to create nutritional estimates.
They discovered that by 7,000 to 8,000 years ago, dogs “were already pretty small, which means they just couldn’t do the things that most wolves did,” Losey said.
This in turn led to a greater reliance on humans for food and a reliance on small prey and scavengers rather than prey larger than themselves that wolves hunt.
“We see that dogs have a marine diet, which means they eat fish, shellfish, seals and sea lions, which they can’t easily get themselves,” he said.
It was noted that old dogs ate fish “in areas of Siberia where the lakes and rivers are frozen seven to eight months a year.”
Wolves of that time and now hunted in packs and mainly ate different species of deer.
– Advantages and Challenges –
These new diets brought both benefits and challenges to dogs.
“Benefit because they could access people’s things, and that’s often simple meals, but it came with the cost of all these new diseases and problems, like malnutrition,” Losey said.
While the new bacteria and parasites they were exposed to may have helped some adapt, some dog populations may not have survived.
Most of America’s first dogs died out for reasons unclear, and were replaced by European dogs — although colonization is not believed to be to blame.
The dogs that survived acquired more diverse gut microbiomes, which helped them digest more of the carbohydrates associated with living with humans.
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