Origin of the domestic dog as the Tibetan people. A population genetic analysis then showed a significant convergence between humans and dogs in Tibet. Like the Tibetan people, Tibetan mastiffs appear to have derived these benefits partially from the EPAS1 gene, acquired through introgression. In 2015, a study found that when dogs and their owners interact, extended eye contact (mutual gaze) increases oxytocin levels in both the dog and its owner. As oxytocin is known for its role in maternal bonding, it is considered likely that this effect has supported the coevolution of human-dog bonding. One observer has stated, "The dog could have arisen only
EDGE species have few close relatives and have been evolving independently for many millions of years. Others like the domestic dog originated only recently and have many close relatives. Species uniqueness’ can be measured as an 'Evolutionary Distinctiveness' (ED) score, using a phylogeny, or evolutionary tree. ED scores are calculated relative to a clade of species descended from a common ancestor. The three clades for which the EDGE of Existence Programme has calculated scores are all classes, namely mammals, amphibians, and corals. The phylogenetic tree has the most recent common ancestor at the root, all the current species as the leaves, and