Quoting John Cowan <jcowan@...>:
> Andreas Johansson scripsit:
>
> > I don't understand why independent innovation should be so unlikely?
> Surely
> > there's plenty of cases where unrelated languages have acquired
> more-or-less
> > exotic sounds independently?
>
> The mystery of clicks is that nobody can figure out how they could have
> resulted
> from a reasonable sound-change in some other language.
Ah. The article in question apparently thought they came from lexicalization of
originally extraphonemomic sounds used in hunting; if that's reasonable
assumption, it may have occured more than once.
Andreas