Dogs diverged from wolves some 100,000 years ago and wolf-human association also started around this time. It is plausible that this association was first initiated by the wolves. Already by this time humans were probably among the most successful hunters of the age. It could have all begun when a propensity for scavenging behaviour led some wolves to take advantage of first following behind human hunting parties and later to ”hanging-out” by human campfires. Intentional and selective breeding of dogs by humans probably started around 50 – 60,000 years ago. By 33,000 years ago dogs were being buried together with their human partners.
Now a new paper looking at the genetic differences between wolves and dogs suggests that ancestral dogs – unlike wolves – had the ability to absorb starchy diets rich in carbohydrates. Scavenging behaviour around hunter-gatherer humans who had already adapted to including grains and grasses in their diet would then be consistent with the start of this genetic trait being selected for among the animals which became fully domesticated much later. True farming started much later at the end of the last ice-age and probably no earlier that 12 – 15,000 years ago. Though the change must have started earlier much of the genetic adaptations in favour of starchy diets may have only happened after this time.
The genomic signature of dog domestication reveals adaptation to a starch-rich diet, Erik Axelsson, Abhirami Ratnakumar, Maja-Louise Arendt, Khurram Maqbool, Matthew T. Webster, Michele Perloski, Olof Liberg, Jon M. Arnemo, Åke Hedhammar & Kerstin Lindblad-Toh, Nature (2013) doi:10.1038/nature11837
Summary: The domestication of dogs was an important episode in the development of human civilization. The precise timing and location of this event is debated and little is known about the genetic changes that accompanied the transformation of ancient wolves into domestic dogs. Here we conduct whole-genome resequencing of dogs and wolves to identify 3.8 million genetic variants used to identify 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. 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
The researchers determined the genetic makeup of groups of dogs and compared the results to those from wolves, concentrating on parts of the genetic instruction book that differ between the two species. As they had expected, the researchers uncovered differences in many genes relating to the brain. But the search also revealed lots of genes involved in starch digestion and metabolism, and in the use of fats. Dogs, the team found, have more copies than wolves do of the AMY2B gene, which produces an enzyme that breaks starch into easily digestible sugars.
Other genetic variants seem to contribute to dogs’ increased ability to convert a sugar called maltose to glucose, the sugar that cells prefer to burn for energy. Yet other genetic changes improve dogs’ ability to move glucose into their cells. Combined, the tweaks alter dogs’ metabolism so they can get more energy out of a carbohydrate-rich diet than wolves can, the researchers conclude. The scientists confirmed the effect of the genetic variants by identifying biochemical differences in starch metabolism in blood and tissue samples from dogs and wolves.