Interestingly from the population statistics alone it is possible to make an argument about the total likely future number of humans that will live. There is debate about whether the reasoning is correct, but it is at least suggestive. See http://en.wikipedia.org/wiki/Doomsday_argument for more.
- "this Civilization thing just keeps collapsing all the time", even a casual glance at history demonstrates that civilizations crash and disappear quite frequently, for a fascinating book on this I would strongly recommend "Collapse" by Jared Diamond http://www.amazon.com/Collapse-Societies-Choose-Fail-Succeed...
- There are still hunter gatherers e.g. the Bushmen of the Kalahari - although whether their lifestyle can survive is open to question: http://www.survivalinternational.org/news/411
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