Why do some species survive for a long time, he wonders, whereas others die out much sooner? And why has the rate of extinction-low throughout most of Earth’s history-spiked upward cataclysmically on just a few occasions?
"You can’t step into the same river twice, for other waters are continually flowing on." To most people it comes across as a nice metaphor, a bit of philosophic poetry. To me it is that and more.