their country for use as slaves. However, it would not begin on a grand scale until Christopher Columbus's voyages to the Americas and the subsequent demand for cheap colonial labour. In 1510, the Spanish Crown initiated Spain's involvement in the Atlantic slave trade, and it was followed over the next centuries by other European states. By 1650, the slave trade was in full force at a number of sites along the coast of West Africa, and over the coming centuries would result in severely reduced growth for the region's population and economy. The expanding slave trade produced significant populations of West Africans living in the New World, recently colonised by Europeans. The oldest known remains of African slaves in the Americas were found in Mexico in early 2006 and are thought to date from the late-16th to mid-17th centuries. As the demand for slaves increased, some African rulers sought to supply the demand by constant war against their neighbours, resulting in fresh captives. States such as Dahomey (in modern-day Benin) and the Bambara Empire (in modern-day Mali) based much of their economy on the exchange of slaves for European goods, particularly firearms that they then employed to capture more slaves. During the colonial era, the Dutch colonial authorities in West Africa were active in recruiting African slaves into the Royal Netherlands East Indies Army (known as Belanda Hitam), as it was believed that Black Africans were more immune than Europeans to the tropical diseases present in the Dutch East Indies. Recruitment changed format after the Atlantic slave trade was abolished by European and American governments in the 19th century. For instance, 1831 was the first year when only volunteers were accepted for the Royal Netherlands East Indies Army. Slavery in the Americas persisted in some capacity even after the end of the Atlantic slave trade, with the last country to abolish the institution being Brazil in 1888. Today, descendants of West Africans make up large and important segments of the population in Brazil, the Caribbean, the United States, and throughout the New World. A modern genetic research study of African-Americans in several major US cities concluded that their common ancestry originated most prominently in western Africa, consistent with prior genetic studies and the history of the slave trade. Colonial period In 1725, the cattle-herding Fulanis of Fouta Djallon launched the first major reformist jihad of the region, overthrowing the local