The first Fido probably wagged its tail in the Middle East.
The largest-ever genetic family tree of dogs and wolves traces dogs’ domestic origin to the region, an international group of researchers reports online March 17 in Nature. The finding fits with archaeological evidence that dogs were domesticated in the Middle East or Eastern Europe and contradicts earlier genetic data suggesting that man’s best friend originated in China.
That earlier work found more genetic diversity in East Asian dog breeds, indicating that the breeds are older and probably represent the earliest domesticated dogs. Although the statistics used in the new analysis aren’t perfect, the study probably gets closer to the truth in unearthing dogs’ origins, some researchers say.
“Nothing ever seals the deal, but this is pretty strong evidence for dog domestication in the Near East cultural region,” says Carlos Driscoll, a geneticist at the National Cancer Institute at Frederick, Md., who was not involved in the new study. “Combined with the fact that all the earliest archaeological evidence points to the region, I think it will be a while before anything more solid comes up.”
Previous research examined genetic material inherited through the mother. That material, mitochondrial DNA, is often used as a molecular “clock” to gauge prehistoric changes in a species, such as domestication. The new work analyzes dogs’ entire genetic makeup to trace both maternal and paternal heritage and discover which parts of the genome contribute to various characteristics.
In the new study, scientists analyzed 48,000 DNA markers, called SNPs, scattered across the genomes of 85 dog breeds as well as gray wolves from 11 different populations around the world. SNPs, or single nucleotide polymorphisms, are letters — also known as DNA bases — in the genetic instruction book that can vary between individuals. When considering spelling changes across the entire genome, East Asian dog breeds are not more genetically diverse than other breeds, the team found.
Modern dog breeds, those that first appeared in the Victorian era, have more genetic kinship with Middle Eastern wolves than with other wolf populations, indicating that dogs probably stem from wolf forebears in that part of the world. Only Akitas, Chinese Shar Pei, chow chow and dingo — all ancient Asian breeds that persist today — hybridized with Chinese wolves. But the interbreeding between the Asian dog breeds and wolves probably happened after dogs were initially domesticated in the Middle East, says Beth Shapiro, an evolutionary biologist at Pennsylvania State University in University Park who was not associated with the new study.
“It makes sense to me that the earliest domestic dogs would breed with wolves when the distribution of the two overlapped, which is what probably happened in East Asia,” she says.
But wolves and dogs have interbred surprisingly rarely, the new study shows. Ancient breeds of dogs — those that first appeared more than 500 years ago and are still kept as pets — have genetic signatures indicating interbreeding with wolves, but modern dogs seem to be all dog.
“We know that wolves and dogs interbreed; I think most people would have expected to see more evidence of such in the dog genome,” Shapiro says. “That said, the strict rules that have been in place since Victorian times to maintain the purity of the various dog breeds are likely to play a key role in making sure that wolf DNA doesn’t make it into the domestic dog lineage.”
Researchers still can’t pinpoint the moment when wolves turned into domestic dogs, says Robert Wayne, an evolutionary biologist at UCLA and one of the leaders of the new study.
“It was probably a pretty fluid interchange for hundreds or thousands of years between protodogs and wolves,” he says.
By peering into dogs’ genetic heritage, the new study also reveals some long-held secrets of breeders. Breeds of dogs that share common jobs, such as herding or tracking or hunting, also share common ancestors, the researchers found.
“We thought there were lots of ways to build a sight hound, or herding dog or terrier,” Wayne says. But the new analysis reveals that breeders used only a few genetic building blocks to achieve their results.