People were keeping domesticated animals since times older than written history. The first domesticated animal was the dog, but it had little influence on the economy. Everything changed with the domestication of sheep, which occured in Southwest Asia around 10,000 BC, and pigs in China only a thousand years later. Raising animals was beneficial not only because of their nutritious meat, but also because many species could consume food that were inedible for humans (like grass or vermin), and therefore acted as "food processors". There were also other gains from keeping live animals: they were the source of milk, leather, feathers, tendons and other usable materials, and with time were used for transport as well.