There are good reasons for any species to think darkly of its own extinction. Ninety-nine percent of the species that have lived on Earth have gone extinct, including more than five tool-using hominids. A quick glance at the fossil record could frighten you into thinking that Earth is growing more dangerous with time. If you carve the planet’s history into nine ages, each spanning five hundred million years, only in the ninth do you find mass extinctions, events that kill off more than two thirds of all species.
But this is deceptive. Earth has always had her hazards; it’s just that for us to see them, she had to fill her fossil beds with variety, so that we could detect discontinuities across time. The tree of life had to fill out before it could be pruned.”