I assume much of Polynesia, especially places like Hawaii, New Zealand and Easter Island, would have been populated by the descendants of just a handful of pioneer settlers who sailed there from faraway islands just over 1000 years ago, which would surely have resulted in a population of very low genetic diversity barely more than that of the inhabitants of, say, Tristan da Cunha or Pitcairn Island (or, at the very most, Iceland). If they do however have a relatively high genetic diversity, how would that have been maintained? On the flipside, if they do indeed have low genetic diversity, is there a high incidence of diseases related to inbreeding like those seen in places like Tristan da Cunha?
Apologies for the long post, I'm trying to ask several questions in one go in as concise a manner as possible.
hi, since this question is mostly about genetics and genetically-related medical issues, it would be worth x-posting to /r/AskScience to see what geneticists have to say
I'll refer you to the wonderfull study by the late prof Oliver Sacks: "The Island of the colorblind".
It focusses on the genetic inheritance of the island of Pingelap, where a particularly hard-hitting typhoon in 1775 severaly depopulated the island, leaving behind a mere 20 survivors. One of these was a high status individual, the local ruler, Nanmwarki Mwanenihsed. Genetic analysis shows he is the likely bearer of a recessive allele for total color blindness (achromatopsia - or "Maskun" in Pingelapese), an otherwhise quite rare condition. Inbreeding, as well as the recessive beeing linked to high social status, allowed the prevalence of the condition to progress up to about 10% on the island. Nowhere else on the planet does the incidence of achromatopsia come even close to such levels.
The condition is more severe than other types of color blindness, in that is comes with an incapacity to deal with bright lights such as that of the sun. Achromats tend to stay inside during the daytime and avoid the sun altogether as it occasions great discomfort. Their night vision, on the other hand, is superlative.