At the risk of being tangenial, I would to know how the uses of clicks and whistles came to be recognized as part of language.
I've read that among peoples with a high level of congenital deafness, sign language emerged from speech. Thus, these individuals can be largely bilingual, applying spoken or sign language as need be.
I speculate that a society with many, malformed larynges could have created this alternative communication -- that was absorbed into the main language.
My hunch begs the question, where did these inadequately formed organs go?
A simpler explanation is that the vast majority of speakers found the click and whistle to be a hassle.