Japanese domesticated chickens have been derived from Shamo traditional fighting cocks.

With the aim of elucidating the evolutionary origin of Japanese domesticated chickens, this study evolutionarily analyzed 85 chicken mtDNA sequences. Thirty-four various ornamental chickens, 42 fighting cocks (Shamo), and nine long-crowing chickens (Naganakidori) were included. Of the Shamo, 18 were sampled from Okinawa, while the remaining 24 were collected in other islands around Japan. In addition, three Southeast Asian Junglefowls were used as a reference to determine the common ancestor of Japanese domesticated chickens. A phylogenetic tree was constructed for the 88 mtDNA sequences revealing that the Shamo group from Okinawa clearly diverged from the other Japanese domesticated chickens studied. This strongly suggests that all Japanese domesticated chickens, including the ornamental varieties and Naganakidori, derived from the ancestors of the Shamo in Okinawa. To create novel varieties of ornamental chickens, intensive artificial selection is imposed on ancestral Shamo populations, resulting in profoundly differentiated Japanese domesticated chickens.