The time scale for evolutionary or genetic change is very long. A characteristic period for the emergence of one advanced species from another is perhaps a hundred thousand years; and very often the difference in behavior between closely relatedspecies-say, lions and tigers-do not seem very great... But today we do not have ten million years to wait for the next advance. We live in a time when our world is changing at an unprecedented rate. While the changes are largely of our own making, they cannot be ignored. We must adjust and adapt andcontrol, or we perish.
Carl Sagan, Dragons of Eden: Speculations on the Evolution of Human Intelligence
human-evolution, intelligence