Pets are a group of animals kept primarily for companionship, that live in a place of residence with an owner or guardian. Goats and sheep were the first domesticated animals, but cats were the first to be kept as pets around 7000 B.C. Pets are distinguishable from work animals, livestock, and laboratory animals because their primary purpose is to provide companionship or entertainment to their owner. However, though different from work animals, pets can also be therapy animals, providing elderly or ill humans with emotional benefits and support. A wide variety of animals can be pets, the most common being dogs and cats, but rabbits, ferrets, rodents, birds, reptiles, fish, amphibians, and arthropods are all kept as pets, as well.