The donkey or ass ("Equus africanus asinus") is a domesticated member of the horse family, Equidae. The wild ancestor of the donkey is the African wild ass, "E. africanus". The donkey has been used as a working animal for at least 5000 years. There are more than 40 million donkeys in the world, mostly in underdeveloped countries, where they are used principally as draught or pack animals. Working donkeys are often associated with those living at or below subsistence levels. Small numbers of donkeys are kept for breeding or as pets in developed countries.