It is generally accepted that slavery or serfdom was gradually disappearing from Europe during the late Middle Ages, even though Christian and infidel continued to enslave one another. Whether this be true or not, a new and more terrible form of human servitude arose as a consequence of the expansion of European powers overseas. In this sense, the Dark Continent was as much a discovery as America. The Portuguese, whose descendants today bear marked Negroid characteristics, found a new source of wealth—new to the Portuguese at least —as they pushed the frontiers of maritime exploration farther south along the unknown coast of Africa. Around the middle of the fifteenth century, it is said, the intrepid Lusitanians, as the Romans once called them, shipped the first boatload of Senegalese blacks to Lisbon.