It sort of depends on what you mean by "advanced". A civilization that simply had pottery 50K years ago, would be considered "advanced" and a major major break

It sort of depends on what you mean by "advanced". A civilization that simply had pottery 50K years ago, would be considered "advanced" and a major major breakthrough. If it did only happen on an island which is today submerged, then probably we will never discover it without major investments to look (which are poor investments since the probability is low). ...and hence, the author's main insight is that low-probability discoveries should be incentivized by prediction markets such that those who believe in the status quo can safely buy their positions - and that anyone who can upend the status quo is richly rewarded. I think that, conceptually, has merit.