The pace of change

"Two billion years ago, our ancestors were microbes; a half-billion years ago, fish, a hundred million years ago, something like mice; then million years ago, arboreal apes; and a million years ago, proto-humans puzzling out the taming of fire. Our evolutionary lineage is marked by mastery of change. In our time, the pace is quickening."— Carl Sagan, Pale Blue Dot: A Vision of the Human Future in Space