When did man start building upwards?

This was a reasonable conclusion since the only known hominid fossils were of brainy species–Neanderthals and Homo erectus. That thinking ... In 1871, Charles Darwin offered an explanation in his book The Descent of Man: Hominids needed to walk on two legs to free up their hands. read more

Generally speaking, when it became impossible to spread an urban population out horizontally -- likely due to the importance of surrounding agriculture -- it became imperative to build upward. read more

My own thoughts/explanation: Now I do understand that early man did suffer a lot of hardship - and some 70,000 years ago, there weren't so terrible many of us around. So perhaps we just never got around to building stuff, what with all the hunting and gathering we were doing - not to mention the cave painting. read more