All dogs have a coat pattern that is thousands of years old and inherited from a now extinct relative of dogs and wolves, scientists have revealed.
The different variations in dogs’ coats are one of their most distinctive characteristics and tracing where they come from has determined why some dogs appear more yellow in colour.
Researchers at the University of California, Davis, have discovered that the genetic mutations behind the different patterns are much older than expected.
Co-author and Professor Danika Bannasch, who has a passion for raising and training dogs, said: “While we think about all this variation in coat colour among dogs, some of it happened long before ‘dogs’ were dogs.
“The genetics turn out to be a lot more interesting because they tell us something about canid evolution.”
Wolves and dogs can have two different types of colour pigment, a black one called eumelanin and a yellow, pheomelanin.
Regulating the production of these two pigments at exactly the right place and time on the body is what gives rise to different colour patterns.
The researchers examined five different dog coat patterns, which were renamed dominant yellow, shaded yellow, agouti, black saddle and black back.
No single genetic mutation could account for all five of these variations, the researchers found.
Rather, dogs needed mutations in two areas of the ASIP gene to get different yellow coat patterns.
This gene is shared with arctic white wolves and are much older than anticipated. It originated in an extinct canine species which diverged from a common ancestor of both dogs and wolves around two million years ago, the researchers found.
Professor Bannasch said: “It didn’t come from modern wolves. It had been around for much longer.”
The genetics of ancient wolves and dogs were tested to confirm the dominant yellow colour had been around for two million years, long before dogs first became domesticated some 30,000 years ago.
The black back pattern was found in a dog sample dating back 9,500 years, which suggests rich variations already existed in canine companions.
Lighter coat patterns were likely to have been advantageous for canines who lived during glaciation periods 1.5 to 2 million years ago, the researchers say.
Natural selection would have then made sure the pattern persisted among the population which eventually gave rise to dogs and wolves.
Co-author Dr Chris Kaelin at the Institute for Biotechnology in Huntsville, Alabama said: “We were initially surprised to discover that white wolves and yellow dogs have an almost identical ASIP DNA configuration.
“But we were even more surprised when it turned out that a specific DNA configuration is more than two million years old, prior to the emergence of modern wolves as a species.”
The findings were published in the journal Nature Evolution and Ecology.
