How do historians know that the people in the kingdoms of ghana, mali, and songhai had common ancestors who migrated to east africa by about 500 b. c.e?
a)they all had genetic characteristics that linked them to the ancient egyptian people
b)they all spoke closely related languages that originally came from the bantu people
c)they all practiced the same religion that originated in the western part of africa
d)they all had tribal connections that identified them with groups from ethiopia