A new study of the genomes of domestic dogs and wolf populations has determined that the domestic dog most likely originated in the Middle East. The finding strongly contradicts earlier mitochondrial DNA studies that put the origins of the domestication in East Asia. In comparing the various genomes of different populations of wolves and dogs, researchers at the University of California, Los Angeles, concluded that dog genomes and Middle Eastern wolf genomes contain the greatest similarity.
The research team, led by Dr. Robert K. Wayne and Bridgett M. vonHoldt, used a genome-wide methodology to determine which populations of wolves were most closely related to dogs. SNP or “snip” chips (devices similar to computer chips than can “read” the DNA down to a single nucleotide polymorphism), looked at 48,000 different locations in the dog genome. SNP chips have been used to scan humans for susceptibility to disease, such as cancer predisposition. In this study, the chips mark regions of common variation within the DNA, allowing researchers to make more accurate comparisons across populations.
It turns out that dogs have more similarities at these 48,000 different locations with Middle Eastern wolves than with other populations of wolves. The findings strongly suggest that today’s domestic dog descends from ancestors in the Middle East.
The original mitochondrial DNA studies looked at only one part of the genome, which is inherited from the female ancestors. Such studies found greater variance in the mitochondrial DNA of East Asian dogs, and since organisms have greater genetic variation at their point of origin, it was then thought that dogs were originally domesticated in Southern China. Because mitochondrial DNA is but a small part of the genome, inferences gleaned from its study may not be as valid as those from a genome-wide study.
Now we know that Middle Eastern wolves likely were among the first populations of wolf to encounter humans; thus it is from these populations that our oldest friend evolved. Researchers also looked for signatures of selection in the genes, and one of the notable genes identified has a human counterpart — implicated in Williams syndrome — which is expressed as extreme friendliness disorder in humans.