Do we know that they were black? North Africa had been in the Roman Empire quite a while and had been previously settled by Greeks and Phoenicians. Even the aborginals had probably settled the area from the Levant rather than directly from sub-Saharan Africa (of course this is no guarantee that they weren't black). If Roman Legionaries had really settled in *significant numbers* then wouldn't it be more noticable in our genes (and I don't mean superficial features like hair or skin colouring)?