My understanding is Buettner is a story teller who doesn't know much about science. His 'findings' are then often portrayed as having some scientific basis but really are much more comparable to 'case studies' in business school-- there's potentially some insight but there's a huge dose of arbitrariness (and lack of rigor) introduced by the author.
In addition to survivorship bias and random variation issues (esp with isolated population's genetic) my understanding is there are arguably many more 'blue zones' than 5; but Buettner chose those 5 as they fit a narrative he wanted to give. E.g IIRC there is a town in Sweden that has very high rate of 90 plus years olds and centenarians, etc. but their dietary (and perhaps climate) pattern didn't fit the story Buettner wanted to tell so he left it out.
In addition to survivorship bias and random variation issues (esp with isolated population's genetic) my understanding is there are arguably many more 'blue zones' than 5; but Buettner chose those 5 as they fit a narrative he wanted to give. E.g IIRC there is a town in Sweden that has very high rate of 90 plus years olds and centenarians, etc. but their dietary (and perhaps climate) pattern didn't fit the story Buettner wanted to tell so he left it out.