It's always been known to me, I don't know how, and now is becoming accepted knowledge by the average person that there existed civilizations, countries, societies, people deep in the mists of time past, during and before the last ice age. One theory is that the end of the ice age resulted in the end of that civilization or society. Some time ago I did a post on the discovery of a city off the coast of India. If interested you can look in my archives, the article was posted on Saturday 4/3/10. The underwater archaeological site that could be more than 9,000 years old was discovered about 30 miles west of Surat in the Gulf of Khambhat (Cambay) in northwestern India. Think about it, at least one city that existed maybe 4000 years more or less before the first acknowledged civilization in "known" history was created. There are more of course, discovered and undiscovered. But if there is just one, it indicates if not proves that prevailing theories are at least incomplete, if not wrong.
Many people have asked, ok, if these mythological civilizations and cities and cultures really existed. With their advanced buildings, weapons, transportation, homes and business's, personal effects, etc. Where are they? Did they use electricity? How did they generate it? Did they have cars, trucks, buses, trains, airplanes? Did they use oil, diesel, gasoline? How did they get it? Machinery to manufacture, made of metal? What metal? How did they find it, make it, turn it into macinery, lubricate it, fix it? These and other questions are obvious, but where are the answers? Where are if nothing else remnants? Why are there only stone, stone buildings, stone tools, stone, stone, stone?
Well one answer is that in libraries, for instance the library of Alexandria, there were alleged to be books, in the form of scrolls, tablets, who knows for sure, of history going back thousands of years. How many thousands unfortunately we have no way of knowing now. There were others but Alexandria is said to be the largest number of books of it's time. It's destruction meant nothing to most people of that time, just as the destruction of let's say the Library of Congress would mean nothing to most today. People haven't changed much. But, it was a destruction of more than a library, even more than the books, it was destruction of history.
Another answer, not a great one maybe, but an answer is the program on the History channel called "Life After People". It's a television documentary series where scientists and other experts speculate about what the Earth might be like if humanity no longer existed, as well as the impact humanity's disappearance might have on the environment and the artificial aspects of civilization. Lets take a look at a little:This is what happens 150-300 years after there are no people.