Scientists generally agree that dogs genetically diverged from wolves between 20,000 and 40,000 years ago. However, the circumstances from which dogs became domesticated are disputed. Until this past July, geneticists and archaeologists believed that dogs were domesticated on two separate occasions: one domestication evolved into Eastern breeds and the other into Western breeds of dogs. However, recent genetic evidence suggests dogs were domesticated only once, and that the East/West split occurred after domestication.
In July of 2017, a study was published which studied several dogs’ genomes (genomes are the map of all of an organism’s genes). This genetic evidence lead the researchers to believe that there was a single domestication event. “We really don’t know where dogs were domesticated and as far as we can tell it happened once,” Pontus Skoglund, geneticist at Harvard Medical School in Boston, Massachusetts. “The researchers estimate that dogs and wolves diverged genetically between 36,900 and 41,500 years ago, and that eastern and western dogs split 17,500–23,900 years ago. Because domestication had to have happened between those events, the team puts it somewhere from 20,000 to 40,000 years ago.” (Nature.com)
One earlier theory suggested that dogs may have begin to evolve alongside farms, developing the ability to digest grain. This theory indicates that wolves who could digest the grain stored on the farms were later domesticated by the farmers. However, the genetic evidence from the dog genomes studied this year suggests that they evolved the ability to digest grain after domestication. The ability to digest grain is marked by the number of copies of the AMY2B gene. The researchers found that dogs who lived thousands of years after domestication still did not have the genetic markers for the ability to digest grain, strongly suggesting that the previous theory (that wolves became able to digest grain, and were then domesticated by farmers) to be untrue.
Archaeologists still believe that dogs were domesticated twice, due to archaeological evidence. In time, I am confident more research will be conducted, and a clearer picture drawn so that scientists can pin down what truly happened thousands of years ago. However, one thing is clear–dog has been man’s best friend for a very long time.
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