Every 100 million years or so, an asteroid or comet the size of a mountain smashes into the earth, killing nearly everything that lives. If ever we needed proof of Nature’s indifference to the welfare of complex organisms such as ourselves, there it is. The history of life on this planet has been one of merciless destruction and blind, lurching renewal.

Sam Harris, Mother Nature is Not Our Friend, in response to the Edge Annual Question 2008

http://www.samharris.org/site/full_text/the-edge-annual-question-20081#sthash.IBMyMOQN.dpuf