Origin of the domestic dog to the domestic dog and modern wolf lineages. The gray wolf is thought to be ancestral to the domestic dog, however its relationship to "C. variabilis", and the genetic contribution of "C. variabilis" to the dog, is the subject of debate. The Zhokhov Island (8,700 YBP) and Aachim (1,700 YBP) canid haplotypes fell within the domestic dog clade, cluster with S805, and also share their haplotypes with – or are one mutation away from – the Tibetan wolf ("C. l. chanco") and the recently-extinct Japanese wolf ("C. l. hodophilax"). This may indicate that these canids retained the genetic signature of
Origin of the domestic dog findings suggest that dogs demonstrating a similar level of performance as 2-year-old children can be explained as a joint outcome of their evolutionary history as well as their socialization in a human environment. Later studies support coevolution in that dogs can discriminate the emotional expressions of human faces, and that most people can tell from a bark whether a dog is alone, being approached by a stranger, playing, or being aggressive, and can tell from a growl how big the dog is. In 2002, a study proposed that immediate human ancestors and wolves may have domesticated each other through a