The history of successful industries has always been a story of cheap labor. Clearly, if you can get people to work for very little, your business will be more profitable. Even in more recent times, you can track the movement of industry -textiles and tuna canning are two striking examples- to the places where the work can be done more cheaply.
But imagine the profits if your laborers work for nothing. In other words, if you use slaves as the European colonial powers of the 16th to the 19th centuries did. Those countries that had colonized the Americas became dependent on slave labor for their survival. Colonial officials believed that the land they had "discovered" in the Americas was useless without sufficient labor to exploit it. However, since there were not sufficient European or Native American workers, large numbers of African people were captured and transported to the Americas to work.
The trans-Saharan slave trade had long supplied slaves from central Africa to work on sugar plantations in the Mediterranean. Having proved themselves competent workers in Europe, enslaved Africans became the labor force of choice in colonial America.
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