The pack of our ancestors caused genetic adaptations in wolves. The animals evolved from carnivores to starch-eating dogs. From a wild animal to a faithful four-legged friend who guides the blind and who can lie in bed with us.
When comparing the DNA of 60 dogs of 14 different breeds with that of 12 wolves, Swedish, Norwegian and American researchers made some interesting discoveries. The results are in Nature this week.
Dogs were probably the first pets. Even before livestock such as sheep, pig and cow walked around our house. But there's still a lot of debate about how the dog emerged from the wolf, when that happened, and where first. Did people take wolf pups for hunting or for guarding their homes? Or is it because man left his nomadic existence behind and exchanged it for a life in one place? According to the Swedish, Norwegian and American researchers, domestication has been accelerated because the ancestor of our current dog learned to digest starch. They link these adaptations to the rise of agriculture some 11,000 years ago. With the rise of agriculture, wolves may have come to the wastelands of settled people to scavenge the dirt. The constant stream of waste was interesting for wolves to keep coming back. In previous research, another group of researchers has stated that dogs split off from wolves about 10,000 years ago and that this must have happened in Southeast Asia or the Middle East.
The research team, led by Erik Axelsson, identified 36 specific genetic regions from 3.8 million genetic variations of the dogs and wolves studied that likely played a role in dog domestication. Nineteen of those regions contain genes important for brain function, eight of which are related to the development of the nervous system. The genes in those brain regions may be responsible for the altered behavior that dogs have towards wolves, such as the decrease in aggressiveness. In addition, the researchers selected ten genes that play an important role in starch digestion and fat metabolism.
The latter genes in particular have played an important role in evolution, according to the researchers. Many crops were grown by farming. And they contain starch. If you wanted to benefit as a wolf from the free food, you had to be able to handle the starch. So there was a selection pressure on the genes that could digest starch.
The researchers found in the genome of the dogs many more copies of the genes responsible for the steps that the digestive system has to take to break down starch than in the wolves studied.
With the advent of agriculture, wolves found themselves in a new environment, where it was crucial to be able to digest starch. But the DNA of our ancestors also had to undergo a number of similar adjustments in order to cope with the starch. The evolution of humans and dogs paralleled the adaptation to a starchy diet. Perhaps the dog genome has even more to tell us about our own evolution.
The researchers conclude that the domestication of the dog occurred sometime between 7,000 and 30,000 years ago. In their article, they mention the discovery of the remains of a 33,000-year-old canine wolf in the Altai Mountains of Siberia. Since that was before the Last Glacial Maximum (26,500 to 19,000–20,000 years ago), it may be that domestication had already started then, but was interrupted by the advancing ice. They also mention the finding of 11,000-12,000 year old fossil dogs in the graves of people in Israel.
UPDATE (March 2013):
The wolf that roamed the Altai Mountains of Siberia 33,000 years ago was more closely related to the modern dog than to the wolf today. Researchers report this March 6, 2013 in the journal PLoS One. That is yet another indication that the dog became a pet very early. The dog may have had a lat relationship with humans in the intervening years. Sometimes they hung out, and sometimes they left and ran wild, only to come back years later.