And how do you shape the harder stone. With even harder stone? And your link is all speculation. They can't say that they had a more advanced technology. So they made guesses. And where are the tools. If they existed, they would have found some by now. In fact, the tools should have survived better than the things they made with them. Also, in order to make precise cuts in stone, you need some sort of device to hold the tool in exactly the same spot. Wood, copper or bronze would all wear out.
Also, you seem to think that basically stone age people were more intelligent than we think. You know who else is intelligent? Modern humans. I heard a person who's job it was to actually cut stone talking on TV once. Speaking of some of the things at Pumapunku, he said that not even we could make such cuts.
I also heard of an explorer or conqueror around the time that South America was first discovered. He sent a letter back to Europe speaking of the Inca walls. He said that they were more grand than anything to be found in Europe. The engineering is mind blowing. How could they have made such cuts in stones that could weigh tens or hundreds of tons and do it so that they would fit perfectly together. It isn't as though they could have kept taking them apart and working them a little more until they fit perfectly together. They must have had help. Here is just one example.
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