This is an incredible writeup. I've visited almost all of these sites to inspect the masonry, spent weeks researching, pestered tour guides and museum workers for oral history, and still I learned things in reading this article.

However there is one aspect which I think is incomplete. When you closely inspect the seams of some of the non-layered works like sacsayhuaman, we are talking about 2mm precision along curved, inconsistent lines of two stones. The when you look at the joints up close, they make the joint between flat cinder-blocks look chunky.

The author posits that this was all hand chiseling and eyeballing, or scribe tools. However I believe there would be occasional gaps or inconsistencies, which simply aren't present in any of the pre-colonial precise works.

One thing I discovered in my research of other central American indigenous cultures (inca was a melting pot of culture and technology) was the use of rope or string, sand, and water to finely cut stones and gems. It is pulled like a circular sand paper and I believe this process would have been used, run between both stones being joined at once, in order to achieve the final tolerances through uniformly wearing the proud aspects of the joint on both sides.

Exceptionaly well documented and written article detailing the well known techniques used to build the iconic stone work in south america. I read an earlier account of a researcher who started investigating pre spanish south american quaries, and how there sudden realisation, while sitting down for lunch, that the round stone to there right, was the hammer used to shape the larger stone to there left and the rows of peck marks ending in raw stone, all of those centuries before. Having worked a bit of stone myself, learning to shape, temper stone drills, and test them for utility, it is very easy to understand how basic pragmatism and persistance, in stone, yields large structures that retain that essential message of we are not messing around in this effort, and your opinions can only embellish this. When considering stone articacts of any scale, it is always best to keep in mind that lithic technology pre dates our "species", and our evolutionary track is directly parallel with it, and there is quite litteraly, mountains of evidence for this.And should you so wish, any modest effort to go look, dig, search the ground, known hunting areas or settlement zones, will yield physical evidence that anyone can examine. our development of technology

This is especially timely as I recently listened to the fall of civilizations podcast on the Incas.

A key answer to an ongoing question I didn't know I had is that only the faces of the stones in the walls are joined precisely. The backs have tapers that are filled in.

I recently came across some geopolymer / alkali activated material stuff on YouTube. Fascinating technology - you can in fact print a house or cast "liquid stone" into ceramic. Seems like companies are using it for expanding foam insulation now too.

The "natron hypothesis" seems to make more sense in Egypt where: Natron and granite powder are just laying around, the blocks are all regular rectangular shape, there are murals that seem to describe the process, and they have large high quality artifacts made from diorite which is the hardest thing around.

Of course that doesn't mean it was used everywhere in the ancient world, and this article does a great job discounting it for the Inca.

I'd love to know if there is some detailed microscopy and chemical analysis underway to see if geopolymer use can be proven in Egypt.

We recently visited Peru — Machu Picchu for a week, then Tambopata (the Amazon) for a week. The Amazonians are still proud of the quality of the stone hammers they find and sell to the highlanders; apparently, there's still "old school" stone masons that insist on using "good" Amazonian hammer rocks.

Mike Haduck has a short series (and a bunch of others too)

MACHU PICCHU "A stone masons commentary" https://m.youtube.com/watch?v=njCStq0Hn58

A great article that starts by not discounting the written accounts that are available.

I am reminded that the Maya language decipherment really moved forward once the written account by Diego De Landa was taken seriously.

Thanks for sharing the marvellous article, is all I can say.

Not gonna lie. I was really hoping for advanced alien technology as the foundation for Inca building techniques.

This was a fascinating read; thank you!