A new family tree of dogs that represents 161 breeds helps shed more light on the evolutionary history of man's best friend. Analysis also traces what could be the living descendants of an ancient canine that was domesticated in the New World before Christopher Columbus's arrival.
In a new study, scientists looked at the DNA of 1,346 dogs to produce one of the most diverse maps that trace the relationship between dog breeds. It reveals the types of dog that people crossed to produce modern breeds.
The genetic map showed that dogs that were bred for similar functions do not necessarily have the same origins. The analysis likewise suggests of the living breeds that have descended from an ancient type of dog that may have arrived in America thousands of years before the historical discovery of Christopher Columbus of the New World.
New World Dogs
Scientists have earlier reported archeological evidence of domestic dogs that arrived in America as early as when people crossed the Bering land bridge that linked Alaska and Siberia. The so-called New World dogs, however, disappeared when dogs from Asia and Europe arrived.
Researchers have attempted to look for the genetic legacy of these ancient dogs in the genomes of modern American breeds but up until now found little evidence. The new study offers the first living evidence of the ancient New World dog in modern breeds.
The new canine family tree revealed that two South American breeds, the xoloitzcuintli and the Peruvian hairless dog, are clustered together, suggesting that these animals may share genes not present in any of the other breeds involved in the analysis.
Study researcher Heidi Parker, from the National Human Genome Research Institute in Bethesda, Maryland, think that these genes may have originated from dogs that were already in the Americas before Columbus's arrival.
"What we noticed is that there are groups of American dogs that separated somewhat from the European breeds," Parker said. "We've been looking for some kind of signature of the New World Dog, and these dogs have New World Dogs hidden in their genome."
Diversification Of Dogs
The clades showed dogs with similar traits. Boxers, Boston terriers, and bulldogs, which were all bred for their strength, are found in one clade. Herders such as corgis and sheepdogs fall into another clade, and another clade consists of hunters such as spaniels and retrievers.
Researchers of the study think that dog breeds went through two major periods of diversification. The first occurred thousands of years ago when dogs were selected for their skills, and the second, which happened a few hundred years ago, bred the animals for their physical traits.
"Combining genetic distance, migration, and genome-wide haplotype sharing analyses, we uncover geographic patterns of development and independent origins of common traits," researchers wrote in their study. "Our analyses reveal the hybrid history of breeds and elucidate the effects of immigration, revealing for the first time a suggestion of New World dog within some modern breeds."
The research was published in the journal Cell Report on April 25.