Wednesday, April 14, 2010

Middle Eastern Origin of Dogs Argued in New Genome Study

A study of the dog genome published in Nature, the pre-eminent publication in biology, reached some surprising and immediately controversial results. For one, disagreeing with prior studies, the new research concludes that “dog breeds share a higher proportion of multi-locus haplotypes unique to grey wolves from the Middle East….” (vonHoldt et al., Genome-wide SNP and Haplotype Analyses Reveal a Rich History Underying Dog Domestication, Nature, vol. 464(8), April 2010). This takes issue with mitochondrial DNA studies that suggested that canine domestication first occurred in east Asia (see Savolainen et al., Science vol. 298, 1610-1613, 2002).

The new research does accept that interbreeding with local wolf populations “clearly occurred elsewhere in the early history of specific lineages.” The researchers sampled 912 dogs from 85 breeds, as well as taking samples from 225 grey wolves from 11 populations around the world. Certain breeds were found to have demonstrated admixture with wolves, particularly breeds with ancient origins that are highly divergent from other dog breeds. Breeds in this group include, not surprisingly, Akitas, Alaskan malamutes, Siberian huskies, and American Eskimo dogs. However, wolf admixture is also found in basenjis, Afghan hounds, Samoyeds, salukis, Canaan dogs, New Guinea singing dogs, dingoes, Chow chows, and Chinese Shar Peis. Some breeds share more with Chinese wolves, some with European wolves, and some with Middle Eastern wolves. Akitas, for instance, show admixture with Chinese wolves, Staffordshire bull terriers with Northern wolves, and basenjis with Middle Eastern wolves. In some cases, the admixture must have been ancient. Dingoes have been isolated from any wolf population for perhaps 4,000 years.

Towards the end of the paper, the researches say that “some ancient east Asian breeds show affinity with Chinese wolves, which suggests that they were derived from Chinese wolves or admixed with them after domestication." This challenges the assumption that has prevailed for some years that dogs were domesticated only once, and harks back to Darwin and others who suggested that canine domestication may have occurred more than once from different populations of canids. The researchers also note that wolves have changed as a result of dogs. The mutation responsible for black coat color was transferred from dogs to grey wolves.

The researchers found “distinct genetic clusters” even within modern dogs based on phenotype and function, including spaniels, scent hounds, mastiff-like breeds, small terriers, retrievers, herding dogs, and sight hounds. Scent hounds include Basset hounds, beagles, and dachshunds. The research behind this six-page paper (supplementary information of 38 pages) is probably only the beginning of a series of papers one can expect from these 36 authors. That’s right! 36 authors.

Supplemental note. I received a comment arguing that American Eskimo dogs do not belong in the category of ancient breeds that show admixture with wolves. The supplemental information to the paper in Nature lists three somewhat distinct groups of dogs in this category. The first consists of basenjis, Afghan hounds, Samoyeds, Salukis, and Canaan dogs. The second consists of New Guinea singing dogs, dingoes, Chow chows, Shar peis, and Akitas. The third consists of Alaskan malamutes, Siberian huskies and American Eskimo dogs. Looking at Supplemental Figure 1, the research indicates that the first group demonstrates significant gene sharing with Middle Eastern wolves, the second group with Chinese wolves, and the third group with Northern wolves. The Inuit Sled Dog (sometimes confused with the American Eskimo dog) is generally thought of as an ancient breed, but the American Eskimo Dog is described by the American Kennel Club as a member of the Spitz family related to the spitz breeds and the white Pomeranian. See Sue Hamilton, "Replica or the Real Deal," The Fan Hitch 4(3) (May 2002). The Nature article does, however, list "Ancient and spitz breeds" as one category so I have to assume, until I hear from one of the Nature article's authors, that they do in fact mean the American Eskimo dog.

1 comment:

  1. "Breeds in this group include, not surprisingly, Akitas, Alaskan malamutes, Siberian huskies, and American Eskimo dogs."

    AMERICAN Eskimo Dogs are definitely NOT part of this group! Inuit Sled Dogs (formerly known as Eskimo Dogs) are.