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Archive - Mar 19, 2010

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Most Domesticated Dogs Originated in Middle East, Study Suggests

Most domesticated dogs likely originated from gray wolves in the Middle East, with only some possibly originating in Europe or Asia, according to a new genetic analysis by an international team of scientists led by UCLA biologists. The team reported genetic data from 912 dogs from 85 breeds (including all the major ones) and 225 wild gray wolves (the ancestor of domesticated dogs) worldwide, including populations from North America, Europe, the Middle East and East Asia. The scientists used molecular genetic techniques to analyze more than 48,000 genetic markers (SNPs) on a genome-wide basis in the dogs and wolves. The team has not yet pinpointed a specific location of origin in the Middle East. The new research results were published online on March 17, 2010 in Nature. In their work, the researchers found evidence for certain candidate genes that might have been important in the early domestication of dogs. There was evidence of positive selection for two SNPs located near genes associated with memory formation and/or behavioral sensitization in mouse or human studies. There was also evidence of positive selection for a third SNP that is located near the dog counterpart of the gene associated with Williams-Beuren syndrome in humans. This syndrome is characterized by social traits such as exceptional gregariousness. The current results were consistent with earlier analyses suggesting that three groups of ancient breeds (origins >500 years ago) are distinct from modern domestic dogs that are the products of the controlled breeding practices of the Victorian era (circa 1830-1900). These ancient breeds consist of an Asian group (dingo, New Guinea singing dog, chow chow, Akita, and Chinese Shar Pei), a Middle Eastern group (Afghan hound and saluki), and a northern group (Alaskan malamute and Siberian husky).

Molecular Basis of Detecting Noxious Chemicals Has Ancient Origin

Chemical nociception, the detection of painful, tissue-damaging chemicals like those found in wasabi, tear gas, and cigarette smoke, is triggered, in humans, by a protein receptor known as TRPA1, which is found in the nose, mouth, skin, lungs, and GI tract. Studying the chemical sensors of fruit flies, researchers at Brandeis University have discovered that flies use their ortholog of the human TRPA1 sensor for the same purpose. Using a combination of behavioral, physiological, and phylogenetic analyses, the scientists found evidence suggesting that this defensive response to noxious compounds has been present across an immense evolutionary time scale and links humans, insects, and many other organisms back to a common ancestor that lived approximately 500 million years ago, said senior author and biologist Dr. Paul Garrity. The ability to detect such noxious compounds, known as reactive electrophiles—a class of compounds that humans find pungent and irritating--is important for animal survival, prompting them to avoid potentially toxic food or dangerous situations. These receptors give animals an advantage in survival by acting as a biological warning system, as it were. In humans, chemical nociception can cause pain and inflammation. "What the study, spearheaded by Kyeongjin Kang in my lab, shows, is that this chemical sense is nearly as ancient as vision," said Dr. Garrity. "While many aspects of other chemical senses, like taste and smell, have been independently invented multiple times over the course of animal evolution, the chemical sense that detects these reactive compounds is different.