Göbekli Tepe – Stone age mountain sanctuary
en.wikipedia.org
en.wikipedia.org
The mind seemed to grow giddy by looking so far back into the abyss of time
This theory, which is the inversion of the conventional theory that the invention of agriculture led to complex society as you describe, is covered in a 2008 Smithsonian article [1] and the Interpretation section [2] of the submitted wikipedia article.
[1] http://www.smithsonianmag.com/history/gobekli-tepe-the-world...
[2] http://en.wikipedia.org/wiki/G%C3%B6bekli_Tepe#Interpretatio...
It also blows my mind that a farmer found it, can't wait until technology can scan the ground and look for human-like construction in a massive scale.