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Excellent presentation on the youtube link. What I found interesting is that they had figured out how to dis-aggregate the rock 40 years ago, but did not know how to re-aggregate the rock. This they discovered about 2 years ago. All by using chemical processes from plants and mineral solutions available in the region. The re-aggregation material turns out to be: guano.
And so now they know to soften, mold, and then harden the stone. Using chemistry, with native materials available to the cultures of the time.
There was also some analysis of those cultures based on archeological findings that indicate they may have been growing amounts of crops specifically for this purpose.
The video is rather long - a bit over an hour - goes very deep into the science. Quite good.