[WMarshal]

"I’m guessing that human ability to change the environmental conditions around them (irrigation, air-conditioning, buildings, growing crops, desalination, heating, etc.) gives us a leg up on the other organisms."

I haven't heard of any birds that can fly at 80,000 feet at mach 3 and see the sunrise in the west by outracing the Sun.

[21twelve]

Obviously there are some events that could set back civilization, or even wipe out the human race. A comet striking the earth for example might wipe us out. A huge eruption such as Yellowstone could set us back quite a ways. I’m guessing another glacial ice advance would cause a huge disruption. And combined with the natural events would be the wars that would ensue to fight for the remaining resources.

My bet is on rapid global cooling. (Technically we are still in “the ice age”, and have experienced the longest warm period ever recorded in the glacial ice record.)