I know, it seems obvious … dogs are not wolves. Dogs have evolved and been bred for over ten thousand years to make them distinct from their wolf ancestors. It’s visible in their anatomy and in their behavior.
Now, research is uncovering the differences in their genetic make-up. According to a study that was published on January 23 in the journal Nature, a surprisingly large part of the variation deals with nutrition.
Scientists in Sweden sequenced DNA from 12 wolves and 60 dogs from 14 breeds. They identified "36 genomic regions that probably represent targets for selection during dog domestication. Nineteen of these regions contain genes important in brain function, eight of which belong to nervous system development pathways and potentially underlie behavioural changes central to dog domestication."
That’s to be expected. The boxer curled at my feet has few behaviors that I would call wolf-like. I don’t think he’d last a week if he were forced to fend for himself in the wild.
What I found most fascinating in this study was the following:
Ten genes with key roles in starch digestion and fat metabolism also show signals of selection. We identify candidate mutations in key genes and provide functional support for an increased starch digestion in dogs relative to wolves. Our results indicate that novel adaptations allowing the early ancestors of modern dogs to thrive on a diet rich in starch, relative to the carnivorous diet of wolves, constituted a crucial step in the early domestication of dogs.
This makes sense when you put it in the context of one of the more popular theories of how dogs became domesticated. The hypothesis goes something like this:
Around the time when many of our ancestors were making the change from a hunter-gatherer lifestyle to agricultural living, wolves sensed an opportunity. Food was abundant around our early farms. Livestock was present and so were rodents and other "vermin." Some enterprising wolves that could stand living in relatively close proximity to people were able to make use of this available food source. Over time, the behavioral and anatomic features that were suited to living near people were selected for, which initiated the transition from wolf to dog.
Meat wasn’t the only type of food available around these farms, however. There was also a lot of grain being produced. The wolf-dogs that could also make good nutritional use of the chunk of bread that was available would be at a competitive advantage over those that couldn’t.
Not only did living in close proximity with and eventually being bred by people alter the appearance and behavior of dogs, it also fundamentally changed their physiologic ability to make effective use of the foods we produce for ourselves.
Dr. Jennifer Coates
The genomic signature of dog domestication reveals adaptation to a starch-rich diet. Axelsson E, Ratnakumar A, Arendt ML, Maqbool K, Webster MT, Perloski M, Liberg O, Arnemo JM, Hedhammar A, Lindblad-Toh K. Nature. 2013 Jan 23.
Image: Doggy Heaven (mashed potatoes) by Laura / via Flickr