Origin of the domestic dog or the result of natural introgression as the dog expanded across Eurasia. In 2018, a study found a small amount of dog ancestry in 62% of Eurasian wolf specimens looked at, that hybridization had occurred across a wide number of timescales and not just recently, however in contrast there was almost no admixture detected in the North American specimens. There was introgression of the male dog into the wolf, but also one hybrid detected which was the result of a male wolf crossed with a female dog. Wolves have maintained their phenotype differences from the dog, which indicates low-frequency hybridization.
Karakachan dog working purebred livestock guarding Karakachan dogs are found in Bulgaria and the United States. The Karakachan was officially approved as a Bulgarian old native breed in 2005. The Karakachan dog may be a descendant of ancient Balkan domestic dogs, possibly since the time of the Thracians. In ancient Thracian treasures, figures were found of big, longhaired guardian dogs with curled tails. The Karakachan dog is part of the origin of the Bulgarian Shepherd dog, with which it should not be confused. Bulgarian Shepherd dog is new construction result of mixing of Karakachan dogs with some big Eurasian breeds - Caucasian