The study reports genetic data from more than 900 dogs from 85 breeds and more than 200 wild gray wolves (the ancestor of domestic dogs) worldwide, including populations from North America, Europe, the Middle East and East Asia. Researchers used molecular genetic techniques to analyze more than 48,000 genetic markers.
The data include samples from Israel, Saudi Arabia and Iran — but they have not pinpointed a specific location in the Middle East where dogs originated.
"Dogs seem to share more genetic similarity with Middle Eastern gray wolves than with any other wolf population worldwide," said Robert Wayne, UCLA professor of ecology and evolutionary biology.
"Genome-wide analysis now directly suggests a Middle East origin for modern dogs. We have found that a dominant proportion of modern dogs' ancestry derives from Middle Eastern wolves, and this finding is consistent with the hypothesis that dogs originated in the Middle East."
"We were able to study a broader sampling of wolves globally than has ever been done before, including Middle Eastern wolves," said the paper's lead author, Bridgett vonHoldt. "In our analysis of the entire genome, we found that dogs share more unique markers with Middle Eastern wolves than with East Asian wolves. We used a genome-wide approach, which avoids the bias of single genome region."
"This study is unique in using a particular technology called a single nucleotide polymorphism, or SNP, genotyping chip; these chips interrogate the nucleotides at 48,000 locations in the genome," said John Novembre, UCLA assistant professor of ecology and evolutionary biology.
"We are able to compare dogs looking at not just one small part of the genome, but at 48,000 different locations. That gives us the fine-scale resolution to analyze how these breeds are related to one another and how they are related to wolves."
Previous genetic research had suggested an East Asian origin based on the higher diversity of mitochondrial sequences in East Asia and China than anywhere else in the world. However, that research was based on only one sequence, a small part of the mitochondrial genome.
"That research made extrapolations about how the domestic dog has evolved from examination of one region in the mitochondrial genome," Wayne said. "This new Nature paper is a much more comprehensive analysis because we have analyzed 48,000 markers distributed throughout the nuclear genome to try to conclude where the most likely ancestral population is.
Furthermore, the findings of the current study are much more consistent with the archaeological record. "We found strong kinship to Middle Eastern gray wolves and, to some extent, European gray wolves — but much less so to any wolves from East Asia.
Eighty percent of dog breeds are modern breeds that evolved in the last few hundred years. But some dog breeds have ancient histories that go back thousands of years.
"We sampled both groups, the modern explosion of dog breeds and some of the ancient lineages," he said. "Our data were aimed at resolving questions about the origin of domestic dogs, the evolution of dog breeds, and the history of dog breeds and relationships to their closest wild progenitor, the gray wolf."
The first dogs that appeared in the Middle Eastern archaeological record date back some 12,000 to 13,000 years. Wolves have been in the Old World for hundreds of thousands of years. The oldest dogs from the archaeological record come from Europe and Western Russia. A dog from Belgium dates back 31,000 years, and a group of dogs from Western Russia is approximately 15,000 years old.
There is one small set of East Asian breeds that does not indicate a strong Middle East origin, showing instead a high level of genetic sharing with Chinese wolves. This finding suggests there was some intermixing between East Asian dog breeds and East Asian wolves; the data do not make clear how long ago this occurred.
Citation: vonHoldt et al., 'Genome-wide SNP and haplotype analyses reveal a rich history underlying dog domestication', Nature, March 2010; doi:10.1038/nature08837
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