The history of slavery spans nearly every culture, nationality and religion and from ancient times to the present day. Slavery was a legally recognized system in which humans were legally considered the property or chattel of another. A slave had few rights and could be bought or sold and made to work for the owner without any choice or pay. As Drescher (2009) argues, "The most crucial and frequently utilized aspect of the condition is a communally recognized right by some individuals to possess, buy, sell, discipline, transport, liberate, or otherwise dispose of the bodies and behaviour of other individuals." In the American colonies and other places, an integral element was frequently the assignment of children of a slave mother to the status of slaves born into slavery. Slavery under this definition does not include other forced labour systems, such as historical forced labor by prisoners, labor camps, or other forms of unfree labor, in which labourers are not legally considered property. Slavery typically requires a shortage of labor and a surplus of land to be viable. While slavery has existed for thousands of years, the social, economic, and legal position of slaves was vastly different in different systems of slavery in different times and places.Slavery can be traced back to the earliest records, such as the Code of Hammurabi (c. 1760 BC), which refers to it as an established institution. Slavery is rare among hunter-gatherer populations, as it is developed as a system of social stratification. Slavery was known in civilizations as old as Sumer, as well as almost every other ancient civilization. The Byzantine-Ottoman wars and the Ottoman wars in Europe resulted in the taking of large numbers of Christian slaves. Similarly, Christians sold Muslim slaves captured in war and also the Islamic World was engaged in slavery. Slavery became common within the British Isles during the Middle Ages. Britain played a prominent role in the Atlantic slave trade, especially after 1600. Slavery was a legal institution in all of the 13 American colonies and Canada (acquired by Britain in 1763). Slavery was endemic in Africa and part of the structure of everyday life. David P. Forsythe wrote: "The fact remained that at the beginning of the nineteenth century an estimated three-quarters of all people alive were trapped in bondage against their will either in some form of slavery or serfdom." Denmark-Norway was the first European country to ban the slave trade. Although slavery is no longer legal anywhere in the world, human trafficking remains an international problem and an estimated 29.8 million persons are living in illegal slavery today. During the Second Sudanese Civil War people were taken into slavery. In Mauritania it is estimated that up to 600,000 men, women and children, or 20% of the population, are currently enslaved, many of them used as bonded labor. Slavery in Mauritania was criminalized in August 2007. Evidence emerged in the late 1990s of systematic slavery in cacao plantations in West Africa; see the chocolate and slavery article.