— From the book “Why We Sleep”

Imagine the birth of your first child.

At the hospital, the doctor enters the room and says, “Congratulations, it’s a healthy baby boy. We’ve completed all of the preliminary tests and everything looks good.” She smiles reassuringly and starts walking toward the door.

However, before exiting the room she turns around and says, “There is just one thing. From this moment forth, and for the rest of your child’s entire life, he will repeatedly and routinely lapse into a state of apparent coma. It might even resemble death at times. And while his body lies still his mind will often be filled with stunning, bizarre hallucinations. This state will consume one-third of his life and I have absolutely no idea why he’ll do it, or what it is for. Good luck!”

Astonishing, but until very recently, this was reality: doctors and scientists could not give you a consistent or complete answer as to why we sleep.

Consider that we have known the functions of the three other basic drives in life—to eat, to drink, and to reproduce—for many tens if not hundreds of years now. Yet the fourth main biological drive, common across the entire animal kingdom—the drive to sleep—has continued to elude science for millennia.”