I don't know much about it, but I've heard about how Europe, Asia and the Middle East have all been ruled by one person at one point. I figure Northern Africa has been captured at least at one point and Southern Africa due to the trade routes. But up until the slave trade was Western, Central or Eastern Africa ever ruled by one person? If so could you tell if they came from another continent or were from African. Also how did those peoples ways of living change after that? Did they continue on as usual or were they introduced to new customs and technology?
I'm not sure where you heard those first few anecdotes, but they are certainly incorrect. Going by typical modern conceptions of the continents, Asia and Europe have never been ruled by a single person. In Asia, the closest would be the Mongol Empire, which did not include most of the southern portion. Likewise the closest in Europe is the Roman empire, which did not control the northern portions. While single empires have controlled the Middle East, it is not a comparable geographical area.