Oldest construction in the world pre-dates all civilizations

What I find interesting is that home sapiens sapiens has existed for atleast 200 000 years yet our oldest constructions aren't older than 12 000 years. Why did it take so long for us to start building? Our bodies didn't change much during this time so we had the capability. Also, why is it that we suddenly start seeing so much activity around 4000 BC [1]?

[1] http://en.wikipedia.org/wiki/List_of_the_oldest_buildings_in...