I remember watching a documentary on the History Channel <oh about what seems like a 1,000 years ago to me>, they were explaining how long ago the Sahara was actually very fertile, a tropical paradise kind of like the Florida Everglades.  This goes in conjunction with my thoery that these areas including the Sahara were affected by a massive war.  The war began 5-6 hundred million years ago, <sh*t wish I had access to my notes>, it broke out once more 30-40 million years ago and broke out a third time around the time of King Arthur...the war drags on now but is entering it's conclusion.  These desert areas (like the Sahara and the Gobi) were once fertile but these guys used weapons of mass destruction 100 times more powerful than the stuff we got, stuff we could only dream of.  Thta's why these areas are blighted areas due to the affects of the weapons that were used, they will never be the same!?^_^