Try to stop thinking for five seconds. Ready?…steady…GO! Okay, now you’re just reading this and not-stopping-your-thinking! So why can’t we stop thinking? Well, this is the handiwork of our old friend, evolution. A long time ago moment-to-moment readiness was necessary for survival. In those days people had to worry about things like lion attacks, leopard attacks, monkeys stealing berries, scorpions, falling rocks, drowning, giant snakes, and so on. This required a brain that was constantly working.
by Prabir Mehta, Science Museum of Virginia