This video contains a few tidbits that point to technologies in use 12,000 years ago that we would not be able to replicate today.
10,500 BC is the date of the Younger Dryas, Meltwater Pulse 1A a.k.a. The Flood, an apparent cataclysm and at the same time a climatic shift causing the end of the Ice Age and the inundation of huge settled regions by a sea level rise of 100 m over a few years.
Plato gives this date as the date for the sinking of Atlantis. So modern science and ancient philosophers agree that something big happened at that time. Turns out, for the Inkas that date marks the end of an era as well: The end of the Hanan Pacha or First World.
Notworthy: Even though the Inkas lost technological capabilities after that, even the constructions of their “Second World” and “Third World” are still amazingly purposeful and solid.
Video also mentions the Chinese Longyou Caves that I’ve never heard before: Huge underground caverns in sandstone rock, a series of huge chambers not connected to each other, of obviously artificial origin, similar to today’s caverns in rock salt mines. We typically make 30 m high caverns these days to get as much rock salt out as we can, those Longyou caves look similar. 2500 years old and unknown purpose and originators.
Why did those ancients build everything from rock? They didn’t. The rock is just the only material that survived the ages. We don’t know what kind of machinery they used to do the construction; the machines are gone. Just like you don’t find the remains of excavators in the basement of Trump tower.
Correction: corrected dates. Younger Dryas was 10,500 BC or about 12,000 years ago; not 12,000 BC.