Dogs really did come from wolves

A new study of dog genetics reveals numerous genes involved in starch metabolism, compared with wolves. It backs an idea that some dogs emerged from wolves that were able to scavenge and digest the food waste of early farmers, the team tells Nature journal. No-one knows precisely when or how our ancestors became so intimately connected with dogs, but the archaeological evidence indicates it was many thousands of years ago. One suggestion is that the modern mutt emerged from ancient hunter-gatherers' use of wolves as hunting companions or guards. But another opinion holds that domestication started with wolves that stole our food leftovers and eventually came to live permanently around humans as a result. "This second hypothesis says that when we settled down, and in conjunction with the development of agriculture, we produced waste dumps around our settlements; and suddenly there was this new food resource, a new niche, for wolves to make use of, and the wolf that was best able to make use of it became the ancestor of the dog," explained Erik Axelsson from Uppsala University.

The Swedish-US team scanned the DNA sequences of the two types of canid for regions of major difference. These would be locations likely to contain genes important in the rise of the domesticated dog. Axelsson's group identified 36 such regions, carrying a little over a hundred genes. The analysis detected the presence of two major functional categories - genes involved in brain development and starch metabolism. In the case of the latter, it seems dogs have many more genes that encode the enzymes needed to break down starch, something that would have been advantageous in an ancestor scavenging on the discarded wheat and other crop products of early farmers. Domestication may have forced dogs into a permanent state of puppyhood . "Wolves also have these genes but they don't use them as efficiently as dogs," said Dr Axelsson. "When we look at the wolf genome, we only see one copy of the gene [for the amylase enzyme] on each chromosome. When we look at the dog genome, we see a range from two to 15 copies; and on average a dog carries seven copies more than the wolf.  "That means the dog is a lot more efficient at making use of the nutrition in starch than the wolf."

As far as the brain development genes are concerned, these probably reflect some of the behavioral differences we now see in the two canids. The dog is a much more docile creature, the likely consequence of early humans preferentially working with animals they found easier to tame.

"Previous experiments have indicated that when you select for a reduction in aggressiveness, you obviously get a tamer animal but you also get an animal that retains juvenile characteristics much longer during development, sometimes into adulthood," said Dr Axelsson. This might go some way to explaining the oft-repeated observation that dogs are permanently stuck in a kind of puppyhood.

http://www.bbc.co.uk/news/science-environment-21142870