Whether he's little and fluffy or gargantuan and sleek, your dog is your pal. He shares your home (and maybe even your bed). He's a member of your family. But dogs were once wolf-like, wild animals. How did they evolve into man's best friend?
There's been a lot of research about canine domestication, but when Amanda Pendleton, Ph.D., a postdoctoral research fellow in the Michigan Medicine Department of Human Genetics, was reviewing some current studies, she noticed something unusual. In some places, the DNA of modern dogs doesn't seem to match DNA from ancient dogs.
Pendleton and her colleagues are working to understand the dog genome to answer questions in genome biology, evolution and disease. Their latest work is published in the journal BMC Biology.
"We convinced ourselves that previous studies found many genes not associated with being a dog but with being a breed dog," says Pendleton in a statement.
Breed dogs began to exist about 300 years ago. Pendleton says they don't fully reflect the genetic diversity found in dogs around the world. Instead, three-quarters of the world's dogs are what are known as village dogs. They roam free, mate freely and scavenge for food from nearby human populations.
To get a clear idea of the true genetic changes in canine evolution, Pendleton and her team studied 43 village dogs from areas such as Portugal, India and Vietnam.
They compared DNA from those village dogs to wolf DNA and that of ancient dogs found in burial sites from about 5,000 years ago. Using statistical models, they isolated genetic changes due to early efforts at domestication.
What these genes do
Once the researchers pinpointed the genes they believed were involved with domestication, they also discovered what those genes did. They found that these specific genes influenced brain function, development and behavior. They also appeared to support something called the neural crest hypothesis of domestication.
"The neural crest hypothesis posits that the phenotypes we see in domesticated animals over and over again — floppy ears, changes to the jaw, coloration, tame behavior — can be explained by genetic changes that act in a certain type of cell during development called neural crest cells, which are incredibly important and contribute to all kinds of adult tissues," explains Pendleton.
One gene in particular, RAI1, stood out. Earlier studies suggest it's involved in circadian rhythm and sleep. The researchers theorize that in dogs, changes in this gene may help explain why domesticated dogs are now awake during the day rather than nocturnal like most of their wolf-like ancestors.