My reading is a bit different. IMHO, the article is not making the assumption you believe it does. Article's logic: * Article assumes common knowledge of a co

My reading is a bit different. IMHO, the article is not making the assumption you believe it does. Article's logic: * Article assumes common knowledge of a collapse, and doesn't bother proving that. * So when did the collapse happen? * Well, the inhabitants were building statues during and right after contact. * So probably afterwards. That 'afterwards' could be right after inhabitants stopped building platforms, but it doesn't have to be for the article's logic to hold! If this is not the case (as you claim), than this just pushes the collapse date forwards from the point they stopped building (after contact). It can't push the date backwards (before contact), because they were building stuff previously (article's actual argument). So if the assumption you mentioned doesn't hold, the article's basic argument - collapse after contact, not as a result of ecological catastrophe - becomes more likely.