Why was Northern Africa isolated from the rest of the continent

The Sahara becomes the almost impenetrable barrier which throughout recorded history has separated the Mediterranean coast and north Africa from the rest of the continent. Hope this help ever thought I'm not a history  I'm a math guy!

Explanation:

china unilaterally claims the entire south china sea as sovereign territory, then builds artificial islands to bolster its claim. it suddenly activates an air defense identification zone over the east china sea, and threatens to down any aircraft that does not report its position. it builds roads into indian territory, then redraws the maps to show that it is actually chinese territory. the people's republic under president xi jinping is quickly becoming the bully of asia.

assuming that by westerners you mean americans. that they were mean and controlling and abusive to its peasants.

explanation: