People have been living underground

Unbelievable? Wild? A bit strange? Since the beginning of time people have been living underground. All history books speak about cavemen. The 17th-century philosopher Thomas Hobbes had a very brutal image of these people and of the human being far away from civilization and called this kind of living “poor, nasty, brutish and short”.
After thousands and thousands of years things have changed a little… 
Today’s earth shelter dwellings are a more friendly and elegant return to nature: comfortable and eco. I wonder what Thomas Hobbes would say about these….