The main types of dog coat patterns we’re familiar with today date back up to 2 million years and may even outdate wolves, according to new research.
Like snowflakes, no two dogs are the same – they vary in shape, size, temperament, and personality. Dog coat patterns are also unique to each individual and are far more evolutionarily complex than you might think.
“While we think about all this variation in coat color among dogs, some of it happened long before ‘dogs’ were dogs,” Professor Danika Bannasch, co-first author of the study, published in Nature Evolution and Ecology, said in a statement. “The genetics turn out to be a lot more interesting because they tell us something about canid evolution.”
Bannasch and colleagues investigated variation in the agouti-signaling protein (ASIP) gene – a gene that determines coat coloring in other mammals by controlling the production of yellow pigment.
As well as yellow pigment, wolves and dogs make a black pigment, and it’s the unique amalgamation of the two that gives each dog its distinct coat color pattern. In fact, just two mutations in the ASIP gene give rise to five different color patterns: dominant yellow, shaded yellow, agouti (bands of different colored pigments on a single hair), black saddle, and black back.
Further research into the dominant yellow coloring revealed that it was far older than expected and has been around since long before dogs were domesticated 30,000 years ago. Studying the genetics of ancient wolves and dogs, the researchers confirmed the genes responsible were about two million years old and therefore weren’t inherited from modern gray wolves.
“[Dominant yellow] didn’t come from modern wolves. It had been around for much longer,” Bannasch said.
Instead, the ASIP DNA pattern of yellow dogs “probably originated from an extinct canid that diverged from grey wolves more than 2?million years ago,” the authors write.
The ASIP genetic makeup of yellow dogs is almost identical to that of Arctic white wolves, a finding which co-first author Chris Kaelin said the team were “initially surprised” at. The team believes this could be explained by the process of natural selection – having a lighter coat would have been advantageous to a canid ancestor living in an arctic environment, hence the coat pattern has persisted in the population.
Meanwhile, the study also found an example of the black back pattern in a dog sample from 9,500 years ago, suggesting that variation in dog coat colors, mediated by the ASIP gene, was present in the early days of dog domestication.
“Our results show how introgression, demographic history and the genetic legacy of extinct canids played key roles in shaping diversity in dogs and modern grey wolves,” the authors conclude.