Grey's Anatomy, Season 4

Meredith:
[voiceover] We like to think that we are rational beings; humane, conscientious, civilized, thoughtful. But when things fall apart, even just a little, it becomes clear we're no better than animals. We have opposable thumbs, we think, we walk erect, we speak, we dream, but deep down we're all still rooting around in the primordial ooze; biting, clawing, scratching out an existence in the cold, dark world like the rest of the tree-toads and sloths.