Currently, we do not have a specific reason for our Civilization existence, but by modern research, it has been proved that ECONOMICS and SCIENTIFIC TECHNOLOGY can be the reason why our Civilization still exists. Olden generation didn't have an access to that. That was why, many Civilizations like Maya Civilization does not exist today.
Since we have technology at your hands, we have better knowledge about how to cope with the natural environment. For instance, consider there is a flood. We know we have to run away to save our lives and leave behind anything is there, as lives are more important. Whereas, the olden civilizations thought that if they don't have things like food, water, dress, ornaments etc. then they can't live. THIS IS THE MAJOR DIFFERENCE BETWEEN THEM AND US.
Also, we have money to trade and get things. While older people had to sell most of their possessions for a single things. Therefore, unluckily, they perished and we exist now.
Hope it helps you...
(by Benjemin)