Israeli dogs participate in CA study on canine origin

By JUDY SIEGEL
April 14, 2010 06:00

Middle East seems a probable origin of the domesticated dog, descending from grey wolves.




Middle East seems probable origin of domesticated

Wolf311. (photo credit: AP)

New genetic data collected by California scientists and reported in the advance online edition of the journal Nature have found that modern dogs likely originated from wolves in the Middle East. But although blood samples have been taken for the research from dogs in Israel, Saudi Arabia and Iran, it is not yet clear in what specific area this occurred.

The online publication Science Daily reported this week that the origin of domesticated dogs – derived from gray wolves – used to be attributed to Asia or Europe, but it now seems this is not true.

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“Dogs seem to share more genetic similarity with Middle Eastern gray wolves than with any other wolf population worldwide,” said ecology and evolutionary biology Prof. Robert Wayne of the University of California at Los Angeles, who was a senior author of the Nature paper.

“Genome-wide analysis now directly suggests a Middle East origin for modern dogs,” he said.

“This is the same area where domestic cats and many of our livestock originated and where agriculture first developed,” Wayne added.

Previous genetic research suggested an East Asian origin for dogs, “which was unexpected,” Wayne said, “because there was never a hint in the archeological record that dogs evolved there.”

“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 von Holdt, a UCLA graduate student in Wayne’s lab who studies the genetics of dog domestication.

“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,” she said.

The team studied genetic data from more than 900 dogs from 85 breeds (including all the leading ones) and more than 200 wild gray wolves worldwide, including populations from North America, Europe, the Middle East and East Asia. They used molecular genetic techniques to analyze more than 48,000 genetic markers, far more than any previous study anywhere.

The study is unique in using a particular technology called a single nucleotide polymorphism (SNP) genotyping chip, which examines the nucleotides at 48,000 locations in the genome, Science Daily quoted UCLA Prof. John Novembre as saying.

The team was able to compare dogs looking at not just one small part of the genome, but a very large part of it.

“That gives us the fine-scale resolution to analyze how these breeds are related to one another and how they are related to wolves,” said Wayne.

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, Wayne noted.

“What we found is much more consistent with the archeological record,” he said.

The UCLA-led team members, who were helped by scientists in Israel, China, Australia, Europe and Canada, said they 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.

“Our findings strongly contradict the conclusions based on earlier mitochondrial DNA sequence data,” Wayne said.

They explained that 80 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,” Wayne 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 archeological record date back some 12,000 to 13,000 years, Wayne said. Wolves have been in the Old World for hundreds of thousands of years. The oldest dogs from the archeological 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, he continued.

“We know that dogs from the Middle East were closely associated with humans because they were found in ancient human burial sites,” Wayne noted. “In one case, a puppy is curled up in the arms of a buried human.”

Some very old strains of dogs – with a history dating back more than several thousand years – may be mixed with modern breeds, enhancing their diversity in certain areas such as East Asia, Wayne said, interpreting the higher mitochondrial DNA diversity in that area of the globe.

Short-legged dogs – there are at least 19 such breeds, including dachshunds, corgis and basset hounds – have short legs due to the appearance of just one unique gene, a mutant growth-factor gene, said Wayne, whose recent research has identified genes responsible for short legs, small size, different fur types and different coat patterns and colors.

“It seems that in dogs, unlike other domesticated species, many of these different phenotypes [observable characteristics or traits of an organism] distill to just a handful of genes” that have been mixed with retrievers, herding dogs and sight hounds to create new breeds.

In man, most differences in height and weight involve many genes, each of which has only a small effect; most of the genes account for only about 1 percent or 2% of variability. Even in agricultural plants, most genes have only a small influence on a single trait.

In dogs, however, one gene that is responsible for differences in size accounts for more than 50% percent of the variation in body size, Wayne concluded.


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