Africa changes you forever, like nowhere on earth. Once you have been there, you will never be the same. But how do you begin to describe its magic to someone who has never felt it?  How can you explain the fascination of this vast,  dusty continent, whose oldest roads are elephant paths?  Could it be because Africa is the place of all  our beginnings, the cradle of mankind,  where our species first stood upright  on the savannahs of long ago?