My guess? Man is his worst enemy. First species with the ability to
annihilate himself. No natural limitations on breading, nuclear
weapons... can even putz with DNA and deliver it in a virus.
Think the particle accelerator might create a black hole, and it all
abruptly ends. Sure beats freezing to death as the government says the
natural gas is needed for war or the egalitarians. Sort of like Russia
in the early 1900's.
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Government isn't the solution to the bad economy, it is the problem.