 Analyses of the mitochondrial DNA of 1576 dogs worldwide revealed that one Kishu and one Siberian husky possessed the same haplotype as a Japanese wolf, indicating past cross-breeding.A more-refined study of Japanese wolf mitochondrial DNA showed that they could be further divided into two separate groups, and that the sequences from one Kishu, one Siberian husky and one Shiba Inu could also be divided into the two groups.These dogs correspond to clade F of the mDNA phylogenetic tree among worldwide dogs, with clade F haplogroup dogs originating from a rare admixture between male dogs and more than one female ancestor of Japanese wolves, which have contributed to the dog gene pool.