Makes you kinda glad we were kicked out, eh?
Regarding the statement that "Clicks are difficult to pronounce fluently and with a single exception no click languages are known outside Africa." ~ clicks really aren't difficult to pronounce ~ there's also a cheek sucking sound that's pretty easy, and one where you do that while opening the mouth.
While in college ages back I had the opportunity to test the various hypotheses regarding these sounds with native speakers of several of these languages who'd come from Angola.
I said the sounds exactly correctly, as I'd done since childhood. In fact, with a little bit of instruction from the Angola guys I was able to merge the "clicks" and "smacks" with other sounds to say words.
I think writers who say such things about "click languages" simply haven't ever tried it themselves.
Actually, it's kind of like we are MADE to make those particular sounds. The only mystery is why such a large part of humanity dropped them!