Out of Asia: The Origin of Dogs

Scientists agree that domestic dogs evolved from wolves (Canis lupus, Figure 1), but disagree on when and where that domestication event took place. Archaeological evidence suggests that humans domesticated wolves 10-15,000 years ago in Eastern Europe and/or the Middle East. This evidence is based on canid remains that look like domestic dogs found in association with human remains. In contrast, mitochondrial DNA and autosomal single nucleotide polymorphism (SNP) data from a large sample of dogs from around the world point to Asia south of the Yangtze River as the center of domestication.

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Figure 1. A wolf (Canis lupus). (From David Rooney/Flickr)

Now an international team of scientists led by Dr. Peter Savolainen from the KTH-Royal Institute of Technology in Sweden may have a more definitive answer. Using dog Y-chromosome DNA samples from 151 dogs from around the world, 12 wolves and 2 coyotes, the team believes that wolves were domesticated in Asia south of the Yangtze River (Figure 2). The genetic data also reveal that there were additional, but relatively minor, genetic contributions from wolves at other locations subsequent to the original domestication event, which indicated that dogs may have subsequently hybridized with wolves.

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Figure 2. (A) Insert - most parsimonious phylogenetic tree of dog haplotypes. Circles represent dog haplotypes, squares are wolf haplotyles and hexagons are coyote haplotypes (black dots are hypothetical intermediates). Circle size is proportional to the frequency of the haplotype among dogs. Colors represent distinct haplogroups. (B) Distribution map of dog Y chromosome haplotypes. Graphs show number of individuals carrying each haplogroup. (From Ding et al., 2011)


The researchers found 28 haplotypes distributed in five haplogroups. Haplotypes are combinations of alleles at adjacent or nearby locations on a chromosome that are transmitted together. The Y chromosome is of particular interest here because unlike other chromosomes, the Y chromosome does not come in pairs. This means that unlike autosomal haplotypes, a male shares essentially the same Y chromosome as his father, making these haplotypes especially useful for tracing lineages.

The haplotype data reveal that roughly 50% of all dog gene pools are shared. Only in Asia south of the Yangtze River is the full range of genetic diversity apparent. This implies that dog gene pools from all other regions of the world likely derive from this region of East Asia. For example, if wolves were also domesticated independently in Europe or the Middle East one would expect to see high genetic diversity in dogs from those locations as well. Instead the genetic diversity was very low in Europe. As the authors state, ”this offers strong evidence that domestication of wolf occurred primarily and possibly exclusively,” in Asia south of the Yangtze River.

The Y chromosome data from the present study along with mtDNA from previous studies also suggest that a relatively large number of wolves, probably several dozen to several hundred, were domesticated. Such repeated domestication suggests that taming wolves was a cultural trait shared by human populations from this region.


References

Ding, Z., Oskarsson, M., Ardalan, A., Angleby, H., Dahlgren, L., Tepeli, C., Kirkness, E., Savolainen, P., & Zhang, Y. (2011). Origins of domestic dog in Southern East Asia is supported by analysis of Y-chromosome DNA Heredity DOI: 10.1038/hdy.2011.114