From pugs to labradoodles to huskies, pets dogs may have genetic differences that makes them more friendly and loyal to humans, scientists say.
Researchers have been comparing dog and wolf DNA to try and identify the genes involved in domestication. They want to understand how a once nocturnal, fearsome wolf-like animal evolved over tens of thousands of years to become beloved members of human families.
Amanda Pendleton, a postdoctoral research fellow at University of Michigan in the US, has been reviewing current domestication research and noticed something peculiar about the DNA of modern dogs: at some places it didn't appear to match DNA from ancient dogs.
"We convinced ourselves that previous studies found many genes not associated with being a dog but with being a breed dog," said Pendleton.
Breed dogs, which mostly arose around 300 years ago, are not fully reflective of the genetic diversity in dogs around the world, she explains.
Three-quarters of the world's dogs are so-called village dogs, who roam, scavenge for food near human populations and are able to mate freely. In order to get a fuller picture of the genetic changes at play in dog evolution, the team looked at 43 village dogs from places such as India, Portugal and Vietnam.
Armed with DNA from village dogs, ancient dogs found at burial sites from around 5,000 years ago, and wolves, they used statistical methods to tease out genetic changes that resulted from humans' first efforts at domestication from those associated with the development of specific breeds.
This new genetic review revealed 246 candidate domestication sites, most of them identified for the first time by their lab.
Upon closer inspection, the researchers noticed that these genes influenced brain function, development and behaviour. Moreover, the genes they found appeared to support what is known as 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 behaviour - 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," said Pendleton.
Many of the genetic sites they identified contained genes that are active in the development and migration of neural crest cells.
One gene in particular stuck out, called RAI1, which was the study's highest ranked gene.
Researchers have been studying the gene's function and role in neurodevelopmental disorders. In humans, changes to the RAI1 gene result in one of two syndromes - Smith-Magensis syndrome if RAI1 is missing or Potocki-Lupski syndrome if RAI1 is duplicated.
In dogs, changes to this gene may help explain why domesticated dogs are awake during the day rather than nocturnal like most wolves. Other genes in dogs have overlap with human syndromes resulting from improper development of neural crest cells, including facial deformities and hypersociability.
These parallels between dogs and humans are what make understanding dog genetics valuable....