There are some amazing theories as to when/where people(s) began grouping, and building "cities". The dawn of civilization as it were.
The accepted idea that Neanderthal man became extinct is a looming question.
It is accepted that 40,000 years ago they vanished. As a kid I was taught they were cave men that ate BrontoBurgers. Today it is more commonly accepted that WE are direct descendants of them.
Tying back into pre-history, there are dozens of examples today of vast cities that spread over hundreds of kilometers potentially dating back over 100,000 years.
While I am not a student or scholar of pre history, I have my own theories...
The main focus (for me) is the ebb, and flow of life on this planet. There have been Numerous extinctions or more precisely "die off-s".
The chicken, and egg problem is nothing compared to whom was-----------------------------------first, and where did they come from...
Think about this... You are a nuclear physicist. Your plane goes down on an island. Are you going to build a fusion powered banana boat or are you going to begin with a hammer?
Compare that to the die off-s through the Earths history. No matter HOW MUCH any civilization knew, it died with them.
I very much like the comment from Mr. Geoff. Knife making was second only to the hammer.+-
Edit:
I can see this thread becoming VERY interesting.