In one form or another slavery has been practiced since the earliest civilizations. Early hunter-gatherers had no use for slaves They did everything for themselves. Having another pair of hands to help them meant another mouth to feed. Slavery or owning another person made no sense to these people. Once men gathered in cities and towns and there was more than enough food, having a cheap supply of labour made sense. This is when the earliest forms of slavery appeared. The main source of slaves was war. When a town was captured, the men were killed and the women were enslaved to work in the fields or as concubines. Slaves made up only a small percentage of the earliest civilizations. These included China's Yangtze River valley, India's Indus Valley, Egypt's Nile valley and the Tigris and Euphrates valleys in Mesopotamia.