There is a lot of shit that went on on this ball of rock before we (Modern Man) came along. For what ever reason, T.H.E.Y. or nature decided to wipe the slate clean and start over a few times in the past.
We have seriously fucked shit up here, so our time is coming too. Some deranged asshole will punch the big red button, and we'll incenerate ourselves. In a couple hundred thousand years after all traces of us are gone, the next experiment will begin.
Wash, rinse, repeat.
It's all happened before. It will happen again.
So say we all....