DWE, you obviously never studied history. Here's the explanation:
Black tribal leaders gathered up black people and either sold them to a black slave trader or sold them directly to potential slave owners. White leaders also gathered up white folks, Yellow leaders also gathered up yellow people, Brown leaders also gathered up brown people and they all sold them either directly or indirectly into slavery. U. S. history teachers at all levels of education fail to teach that slavery was NEVER confined solely to black people being enslaved. Again all peoples of of all colors at some point in history have been enslaved by their same colored brethren. Now go to the library (or as dummies would say, liberry) and learn the facts! Now Go!