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:

legislative branch:

one of the three branches of government divided between the senate and the house of representatives.

- creates or makes laws

- power to override a veto

executive branch:

one of the three branches of government, headed by the president.

- enforces or carries out laws

- power to veto a bill sent to it by congress

judicial branch:

one of the three branches of government, headed by the chief justice of the supreme court.

- interprets laws

- power to declare laws or actions by the government unconstitutional

straight down to hell mate