[nradov]

What is the extraordinary claim? If we look at the evidence from a neutral perspective with no preconceived notions, the evidence for a newer construction date doesn't seem particularly stronger than an older one. Modern Homo sapiens has been around at least 160,000 years so they could have potentially been building structures at any time after that. We really don't know how long it took humans to develop basic masonry and only a tiny fraction of the artifacts from the deep past have ever been found.

I fail to see how Bayesian priors have any relevance here. And numbers were assign are going to be largely guesses not based on real hard evidence.