1) Why some languages, for example, Polynesian, have so few consonants, while Caucasian have dozen of them? Could we infer that older Human languages have few or many phonemes?
2) Is there any study about growing or reduction of phoneme diverstiy along the evolution of language? Why and how can phonemes be "created"? A people can "add" phonemes to its lanaguage, or additional sounds always came from adstratal or superstratal source?
3) Why it seems that Western IE proto-languages had no palatals?
4) Is there any study about distribution of particular phonemes across the world? For example, rounded vowels (ö/ü) or uvular R?
Thanks,
Joao S. Lopes