Global Extinction
Massive extinctions have taken place for millions of years, so long ago that life had time to start again from zero, leaving behind creatures that were lost forever in the transformations suffered by a young, inexpert and changing.
We are the most efficient agent of a phenomenon which is as old as life itself: the extinction of species. But we are becoming so efficient in our role as destroyers that, as we begin to understand the interdependent mechanisms of life on earth, we are realizing that perhaps our own activities could end up leading our species along the road to extinction.