Based on what? His statistics that shows extremely high variance? I bet he would be laughed out of any statistics department trying to extrapolate the linear model that he demonstrates. And let's not forget, that Navajo traveled a significantly longer distance from Africa than Hawaiian did, why does Navajo though have about 33 some consonants while Hawaiian only has 8?
Speaking as a statistics PhD, I can say that the correlation he finds between distance and phoneme diversity is pretty robust -- real data from complex systems is always going to be noisy. The model used could probably be improved (eg using a definition of distance that better reflected migration routes) but that would require making a lot more assumptions.
And let's not forget, that Navajo traveled a significantly longer distance from Africa than Hawaiian did, why does Navajo though have about 33 some consonants while Hawaiian only has 8?
Cherry-picking extreme cases does not prove that a trend does not exist. But, as argued in the paper, the Austronesian languages could be expected to see a very strong founder effect because of the island-hopping style of migration. This has been studied extensively and there is genetic and cultural evidence to suggest founder effects.
No, I am not arguing this, and I'm fairly confident that the assertion made by the paper is true, that Proto-World existed and it was spoken in Africa. However, we totally lack enough evidence to suggest that this is known... right now it's just something that we imagine is a really good hunch.
This is evidence that supports the hypothesis. It doesn't prove it, by any means, but it is consistent with the hypothesis.
This paper is the first application of the "founder effect" on phonology... but it requires that a founding population have missing phonemes when they found a new population. The likelihood of this occurring is only in rare phonemes, and even then super unlikely because even rare phonemes are reasonably common given the size of vocabularies.
There are better explanations for why phonemic diversity decreases and "founder effect" is a fairly bad theory. Hawaiian has 8 consonants while Maori has 10, but Hawaiian has heavy allophonic matching between "t" and "k", and "w" with "v", both of which suggest that there was a consonant shift in the Hawaiian/Maori proto-language that caused a phonemic collision in Hawaiian.
We don't need the claim that "Hawaiian when it left didn't bring over any of the words that had 'k' or 'wh' in them"...
You may well be right that it is not a strict founder effect in action here in the sense that there weren't some phonemes that go left off the boat, as it were. But it is quite possible that there was some other cultural force in effect as new colony established themselves causing the same bottle-necking that is seen with a strict founder effect.
I think linguists often get lost in the complexity of the individual systems they study (often to a very impressive level) and are unable to step back with a study like this and see a broader trend. Indeed, a very broad and quite weak trend like this probably doesn't really tell a linguist much if they are interested in relationships between languages of the past few thousand years because it has very little predictive power. But I see it as quite a nice use of statistical reasoning in that it ignores a lot of the details, simplifying the data down to a point where it is easy to work with but still contains some signal that can reasonably be interpreted.
Your argument for the founder effect works for words, but not necessarily for phonemes. In order for a phoneme to be dropped by founder effect, the phoneme would have to occur in none of the words that the founders brought over. The idea of a phoneme rare enough in a vocabulary large enough for use by a small colony seems unlikely...
Plus, the Scandanavian languages lost the interdental fricative, while the colony of Iceland kept the interdental fricative... poor standing for your "founder effect" notion...
Founder effects can occur with large groups, too. Think of two towns that speak the same language but have some noticeable variation between the two, for example, in one town they use the voiceless dental plosive, the other they use both the interdental fricative and the voiceless dental plosive. If these towns become isolated from each other evolving distinct languages, one will have fewer phonemes than the other. This is the founder effect.
other then the occasional sporting event
This is crucial --- cable would have nothing if it weren't for sports.