"So we started with mud bricks that were used in the enclosures during the 2nd Dynasty. They did not have stone [working, hard metal] tools so... they used mud bricks. Then... the invention of the first limestone bricks by agglomeration. The technology improved into bigger and bigger... limestone blocks, and then suddenly, 800 years later, they had tools to cut the stone. No! They returned to pyramids made of mud brick. So this is something is not capable of explaining. It is something that ic technology is capable of explaining, essentially because here we had a stop of the use of this technology to make stone."