One concept is the Fossil evidence, and I suppose another would be the cyclic orbits of heavenly bodies, such as Astroids and comets. Actually, we are in the middle of one of the greatest mass extinctions in the Earth's history. Even as far as the Weather goes, it is about two thousand years past time for a big freeze. Over the past 2.5 million years, the norm has been colder, so what Human kind has been experiencing is abnormal. It could begin to change at any time, even within our lifetime. We have grown fat and happy, so to speak, in two thousand years. global warming is not being caused by us Humans, that is a profit generated agenda, purely speaking. but any number of factors effect our existence, so there are of course more concepts than laid out here.
But he only needed two Please Register or Log in to view the hidden image! But I should also have mentioned humanity, you're right Please Register or Log in to view the hidden image!
Hehe.. I was thinking something similar, but heh.. Please Register or Log in to view the hidden image!