re: #66 KGxvi

something would have shown up in the archeological record by now.

Hard to see any civilization arising without going through an extractive period. We have extracted huge amounts of minerals and dispersed them around the world, obviously destroying the natural deposits found in the Earth. In particular, large banded iron deposits laid down in Precambrian times, which serve as the major deposits used in mining iron ore, have not shown any incident of earlier mining. They are easily extractable so any earlier civilizaton should have mined them, leavoing a lot less for us.

And rarer mineral deposits (ie gold) do not appear to have been touched by any earlier civilizations before humans found them. So, if there were earlier civilizations, they had to arise without really using much of the Earth’s natural resources. IMHO.