Fiber is a thread-like material that can be found in natural or artificial forms. Natural fibers are derived from various animals, plants and can also be produced by insects. These fibers have been used since prehistoric times and are currently being produced today. The most commonly used natural fibers are linen, wool, silk and cotton. They have been woven together to create fabrics for clothing and other items. A natural protein fiber, called wool, was discovered before 10,000 BC and woven into fabrics by 1900 BC. Wool comes predominantly from sheep, but is also found in other animals such as llamas, alpacas, camels, and goats. Northern European tribes spun wool using a crude spindle, which was a stick with a ring of stone or clay attached to the end to produce yarn. They also turned wool into cloth by weaving the thread in a crisscross style. Some humans 8,000 years ago had domesticated sheep specifically for wool production and other uses. By 4,000 BC the city of Babylon, also known as the "Land of Wool", had bought and sold woolen fabrics important to their society. Over the years spinning and weaving machines were constantly improved such as the Jenny spinning mill built in 1767 with many spindles placed side by side allowing it to drive 120 spindles at once. Wool weaving became more machine-based rather than traditional hand weaving (“History of Wool,” n.d.). To create wool fiber, there is a process of cutting the animal's hair which is usually done manually by a shearing specialist. After cutting, the sheared wool is cleaned and brushed to manually straighten the fiber strands. The wool is then fed into a card where it passes through numerous bristle rollers and is spun. The carding process separates the wool into small pieces and cools it into coils at the end of the machine. Soon the wool is spun into thread and woven into cloth. Before this mechanical process, many women known as spinsters took on the task of manually turning wool into cloth. Wool is commonly used to create cool-weather sweaters and coats (“History of Fibers,” n.d.). The fiber repels water well and the fabric feels dry in humid or wet weather conditions. One disadvantage of wearing wool is that it attracts moths and roaches that feed on the fabric.