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
Dog type were described as species by Johann Friedrich Gmelin in 1788, and by Robert Kerr in his English translation of "Systema naturae" ("The Animal Kingdom") in 1792. Today the species Linnaeus named are identifiable as dog types, not species or subspecies. Some, such as "Canis aegyptius", a hairless dog type of Peru, have been documented and registered as breeds (Peruvian Hairless Dog). There are only two categories (subspecies) of domestic dog, "Canis lupus familiaris" and "C. l. dingo", recognized by the International Code of Zoological Nomenclature (ICZN Code). Beginning with the advent of dog shows in the mid-19th century in England,