The history we most often hear in school is only a tiny sliver of the true story of this planet.  I have no special knowledge of the past, but as a thoughtful analytical person it is clear that most of the real history remains in the shadows.  Given the bits and pieces that have been either recently discovered or re-discovered, some common threads seem to emerge.

I propose serious consideration of the following:

1. Civilization
   1. A number of different hominid groups have developed sophisticated civilizations.  Given that hominid history is millions of years old, it seems presumptuous to assume that any evidence of culture or technology found prior to 40,000 years ago must imply human participation.  We are the last surviving hominid group (probably) but we were certainly not the first.
2. Ice ages have defined major cycles of civilizations.
   1. Civilization has risen and fallen in a number of catastrophic cycles before the end of the last ice age.
   2. Major ice ages concentrate hominid populations in equatorial regions and dramatically shrink the population and under minds civilization.
   5. Then the destructive thawing and climate change process causes yet another traumatic displacement and washes away much of the structures remnants had managed to build.
   7. Humans predominantly settle near bodies of water. So by definition, our ancient civilizations would be lost under the water when ice ages are over.
   8. Decay, adaptive reuse, deliberate destruction and the dynamic transformation of our planetary surface through catastrophe and geological processes tend to erase all but the most monolithic traces of past civilizations.
3. Proof of ancient civilization have been lost
   1. both underwater
   3. under existing cities
   4. decay over tens and hundreds of thousands of years
   5. deliberate destruction
4. Geology
   1. What circumstances could have allowed Antarctica to be ice free?  http://www.nature.com/nature/journal/v458/n7236/full/nature07867.html