> It seems like we've been pretty smart for a long long time. There are civilizations all over the globe that rose, fell, and died, and we will never ever know of them. The idea of 'civilization' is ancient, it seems.
I've wondered about that a lot, actually. If homo sapiens have been around for ~200k years (according to wikipedia), what were we doing for the first 185k years? What changed ~15k years ago that we started building cities, constructing tools, etc., and why did it take 185k years to happen?
On a larger time frame, how many species have lived and died and had every trace of their existence crushed and melted down by plate tectonics?
It's fascinating to think about, and a little sad that we'll never know the answer.