What is your source for claims of trade?
There is no evidence for trade between Europe and Africa going back thousands of years.
Sub-Saharan Africans never developed a written language, this would seem to be a not quite vital, but certainly helpful thing when engaging in trade.
Thousands of years ago there was very little, if any, industry to speak of in sub-Saharan Africa. What was being traded?
Edit:
The poster above referenced black Africans, a distinct population from north Africans, and "cross-continental" trade implying a great distance and regular contact between the African and European races.
While some could argue that it is technically cross-continental as we understand geography today, I don't believe a good faith interpretation(in this discussion) of 'cross-continental trade' includes trade conducted in ancient Mediterranean world.