One of the main reasons given for the success of homo sapiens over other species of humans is that we were able to share expertise between tribes and communities. We also had larger communities that led to a more diverse collection of skills. Shortly after, specialisation occurred. Kind of like: "you are a good axe maker, I'm a good spear maker. Let's make what we are good at and swap them as needed".

Unfortunately nowadays "specialisation" has become a means to keep products and manufacturing processes to one's self rather than for the mutual benefit of the society or group. I agree that those who invent products should have an exclusive right to make them for a period until they have recouped their investments such as research etc, plus a profit on their inventions. Today, however, it has gone too far and is impeding progress rather than encouraging it. Everlasting copyrights and patents have become the bane of our modern world.

One of the reasons given for the demise of other human species was exclusivity. They usually lived in small family groups and shared very little with their neighbours. So they stagnated and did not progress in the same way that we did during the Paleolithic age. During the Mesolithic and Neolithic ages, we obviously progressed far more quickly than has been previously recognised.

The above link is a pretty-much tongue-in-cheek look at how humans did progress far quicker than conventional anthropological archaeology recognises today. Perhaps one reason we are so incredulous at the achievements of stone-age man is that we are assuming that our selfish and insular behaviour today has always been the norm. Maybe our "modern society", developed over a couple of thousand years as opposed to tens, perhaps scores of thousands of years, is actually an aberration rather than the norm.

It is increasingly more difficult to deny that there are "missing episodes" in the reported history of mankind, going back tens of thousands of years and these huge engineering projects required a great deal of co-operation not only in the societies that built them but also with neighbouring communities. This is evidenced by the amount of imported materials used in the constructions - materials from areas that were contemporaneously inhabited by other peoples.

Certainly, they could not have been achieved (given the timescale and the tools available to them) whilst at the same time spending huge resources on military conquests, wars and bickering with their neighbours or by keeping their individual skills and techniques to themselves.