Starchy genes made dog into Man's best friend, study reports

Jan 23, 2013 by Barbara Bronson Gray, Healthday Reporter
Why some wolves became dogs
Key genetic changes allowed certain canines to eat starchy scraps left by humans, study shows.

The question of how some wolves evolved into the trusty dogs that work on farms, lead the blind and curl up on pillows in bedrooms has remained largely unanswered. Until now.

An international team of researchers used complex genetic analysis and an understanding of archeology, ecology, biochemistry and agricultural science to discover that adaptations that allowed dogs to thrive on starch-rich diets was central to the domestication of canines.

"I think the domestication of dogs is especially interesting because we have such a special relationship with dogs; they stand out in terms of being domesticated animals, as they become part of our families," explained study author Erik Axelsson, an assistant professor at Uppsala University, in Sweden.

The transition from wolf to dog was relatively simple. In early agricultural settlements, "humans began to gather their trash into small waste dumps, which might have attracted wolves because the waste dumps provided a relatively constant supply of food," Axelsson explained. "That sort of nutrition must have been the leftover remains—of what they ate, which included starch."

To be an efficient scavenger, a wolf had to have an effective method of digesting starch, he said. "Some wolves were slightly better than others at digesting starch and had an advantage. A natural selection process created animals that we later called dogs."

Axelsson said it's actually easy to envision how it might have happened. To be able to effectively grab food out of the waste dump, dogs had to be comfortable around people. "Imagine a shy wolf running away every time it saw a human," he noted.

As for when the evolution of wolves into dogs may have occurred, Axelsson said it's hard to give a well-defined time. He said both archeological and genetic data suggests it could have happened anywhere from 6,000 to 30,000 years ago.

While the evidence isn't conclusive, Axelsson noted that the genetic data combined with the researchers' collective understanding of archeology and other fields fits their conclusion: dogs' increased ability to thrive on starchy food, as opposed to the meat-rich diets of wolves, represents an important step in domestication. The research was published in the Jan. 23 issue of the journal Nature.

To understand the genetic changes associated with the transition from wolves to dogs, the researchers compared whole-genome sequences of domesticated dogs with those of wolves. Genomes are a full set of chromosomes representing all the inheritable traits of a single organism.

From 3.8 million genetic variants, the researchers identified 36 targeted genetic regions that likely played a role in the domestication of dogs. Eight of these regions had genes related to nervous system pathways and 10 had genes involved in starch digestion.

Axelsson explained how the researchers know when they've identified something critical through the genetic analysis: "When a mutation occurs, it will arise in one individual and if the mutation confers a good trait—in this case being able to digest starch—then in a relatively short time period, everyone will carry that mutation. Usually there are lots of other mutations, too, but nearby that mutation for the good trait, there won't be any other mutations or genetic variations in that region."

So, "When all dogs look similar on the genetic level, then you have a signal, or a sign, that selection is happening," Axelsson said.

The researchers said that the study results show how coping with an increasingly starch-rich diet when humans began to grow their own food caused similar adaptive responses in dog and human.

While this may all sound quite academic, Dr. Amber Andersen, a veterinarian at Point Vicente Animal Hospital in Palos Verdes, Calif., said the research provides practical guidance about what your beloved dog should be eating.

"There has always been this argument that dogs are meant to eat meat, but now I can feel even more confident telling my clients that dogs have adapted to eat starches and can eat them in kibble, for example, unless there's a specific allergy or a chronic medical condition where we're concerned about starch digestion," Andersen said.

Andersen added that the study also points to the importance of understanding that people and their dogs and other pets inhabit a common environment, including the home, the backyard and the community. "Since the very beginning, there's been this shared environment," Anderson noted.

Explore further: Danish museum discovers unique gift from Charles Darwin

More information: To learn more about the history of dogs, go to the Archaeological Institute of America.

Paper: dx.doi.org/10.1038/nature11837

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Kron
1.7 / 5 (12) Jan 23, 2013
In front of an untrained, non-domesticated dog place a bowl of kibble and a plate of meat. See which the dog is naturally inclined towards.

Dogs evolved from subservient beta wolves. The dominant alpha wolves run their wolf packs. The beta wolves were beaten in combat and ran from the pack. Their need for companionship led them to explore relationships with humans. Out of fear of being beaten again, and cast from their new homes, the sub wolves listened and followed the instructions of their human masters.

Life at it's very core is about adaptation. Any animal with time can adapt to a new food source. The change in food supply did not cause evolution of wolves into dogs. The evolution was a result of natural selection. The wolves that lived amongst humans were a kinder, gentler, more subservient breed. They didn't become gentle and kind because of the type of food they ate as the study suggests.

This study funded by dog food producers perhaps?
Kron
1.4 / 5 (10) Jan 23, 2013
I know two types of vegans, all were meat eaters before their lifestyle change.
1. Aggressive vegan, dominant type. These people were naturally aggressive before their dietary change and have stayed that way after the change.
2. Passive vegan, submissive type. They've also kept their passive nature following their dietary change.
The diet does not change the nature of the beast.
dogbert
1.4 / 5 (9) Jan 23, 2013
The article supposes that domestication came after man began to live in cities -- that is to say as well, after man began to farm.

This is certainly possible. It is also possible that dogs found an association with man to be beneficial before man decided to farm.
Pediopal
1.7 / 5 (11) Jan 23, 2013
Of course the veterinarians are happy they can tell their clients they can feed kibble. Veterinarians sell dog food at very high mark-up. Raw diet including meat and bones do not hurt dogs. One of the reasons dogs has allergies, epilepsy, and other chronic ailments are because they CANNOT digest grain. Dog food companies FUND veterinary schools and promote their products all the way through veterinary school. Wolves and domestic dog DNA is almost indistinguishable and trying to make people believe dogs can thrive on starchy food is ridiculous.
Czcibor
1 / 5 (7) Jan 24, 2013
Very interesting observation, however I think that this conclusion is a bit too far going, at least from data presented in article:
"Axelsson said it's actually easy to envision how it might have happened. To be able to effectively grab food out of the waste dump, dogs had to be comfortable around people."

Domestication could have happened a while earlier. When people moved towards farming, their animals simply had to change their diet with them. This process led to long term accumulation of DNA changes, that lasted for thousand years.

(Or maybe a desperate scientist had to say that as simple as possible, with an interesting story because that was what a journalist expected)
PJS
not rated yet Jan 24, 2013
One of the reasons dogs has allergies, epilepsy, and other chronic ailments are because they CANNOT digest grain.


Allergies are entirely an effect of the immune system, and have nothing to do with digestibility...