For serious discussion of the controversies, approaches and enigmas surrounding the origins and development of the human species and of human civilization. (NB: for more ‘out there’ posts we point you in the direction of the ‘Paranormal & Supernatural
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Altitude is not problem, because after adaption people can lives with low oxygen. Moving stones is simple. One inch manilla rope can withstand 4 tonnes, and one man can pull 100 kg. Without special engineering techniques you need 25 ropes and 1000 muscular men to move a 100 tonnes block. But art is more difficult and Tiwanaku is a good example; they cut and moved large blocks, but their art was undeveloped.