Sleep consumes time we could spend foraging and it exposes us to predators. It’s a waste and a risk. So why do humans sleep? Why didn’t nature design us for continual activity and vigilance?
In the October 18, 2013 Science, researchers offer an answer: sleep enables house cleaning. Studies of mice show that sleep sweeps the brain of toxic metabolic waste products.
Ergo, at the day’s end we can say to our loved ones: Good night. Sleep tidy.