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Health

The dog as pig

Gene ExpressionBy Razib KhanSeptember 9, 2009 2:21 AM

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There's been some buzz over a recent paper, mtDNA Data Indicates a Single Origin for Dogs South of Yangtze River, less than 16,300 Years Ago, from Numerous Wolves. This is tracing the maternal lineage, and suggests that that lineage is most diverse in southern China (just as human lineages tend to exhibit the most diversity in Africa). Here's the abstract:

...We therefore analysed entire mitochondrial genomes for 169 dogs to obtain maximal phylogenetic resolution, and the CR for 1,543 dogs across the Old World for a comprehensive picture of geographical diversity. Hereby, a detailed picture of the origins of the dog can for the first time be suggested. We obtained evidence that the dog has a single origin in time and space, and an estimation of the time of origin, number of founders and approximate region, which also gives potential clues about the human culture involved. The analyses showed that dogs universally share a common homogenous gene pool containing 10 major haplogroups. However, the full range of genetic diversity, all 10 haplogroups, was found only in south-eastern Asia south of Yangtze River, and diversity decreased following a gradient across Eurasia, through 7 haplogroups in Central China, and 5 in North China and Southwest Asia, down to only 4 haplogroups in Europe. The mean sequence distance to ancestral haplotypes indicates an origin 5,400-16,300 years ago from at least 51 female wolf founders. These results indicate that the domestic dog originated in southern China less than 16,300 years ago, from several hundred wolves. The place and time coincide approximately with the origin of rice agriculture, suggesting that the dogs may have originated among sedentary hunter-gatherers or early farmers, and the numerous founders indicate that wolf taming was an important culture trait.

The more interesting (from a Western perspective salacious) is the speculation that domestication was driven by the utilization of dogs as potential food rather than helpmates:

Finally, it is worth noting that, in contrast to most other parts of the world, dogs have been used as food on a large scale in southern East Asia, from ancient times until today (Higham, Kijngam and Manly 1980; Simoons 1991; Ren 1995). It may therefore be speculated that the wolf was domesticated for its use as a source of food rather than for hunting, guarding or companionship as mostly suggested, perhaps under influence of a European non-dog eating perspective. In nature, wolves (in contrast to the omnivorous dogs) are practically strict carnivores (Thorne 1995), and feeding meat to a meat animal may seem an illogical expense. However, wolves are able to obtain all necessary nutrients from vegetable material (Thorne 1995) and Italian wolves, whose habitats have been severely encroached by human settlement, are estimated to obtain 60-70% of their food from garbage dumps, including a large proportion of vegetable substances, e.g. spaghetti (Boitani 1982). Possibly, the transition in behaviour from carnivore to omnivore was an early step in the domestication process, perhaps in an initial "self-domestication" process (Crockford 2000) in which wolves approached human camp sites in search for food left-overs.

Nick Wade in The New York Times runs with that angle, In Taming Dogs, Humans May Have Sought a Meal, but he has an interesting quote from other researchers:

A team of American researchers is examining the genetics of dogs and wolves with a so-called dog chip, a device that is programmed to recognize thousands of different sites on the dog and wolf genome, not just the mitochondrial DNA studied by Dr. Savolainen. The data have not yet been published, but some of it "doesn't agree completely" with an East Asian origin of dogs, Dr. O'Brien said.

I believe that the genetics of both cows and pigs show evidence of hybridization between various strains. Wolfs and dogs can still interbreed, so it wouldn't be surprising if we see this as dogs expanded from one region to many. Cite: Molecular Biology and Evolution, doi:10.1093/molbev/msp195

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