Why do people sleep? And other unanswered questions

BIRDS DO IT. Bees do it. People do it, though often less than they would like to. Owls do it in the daytime. Even Caenorhabditis elegans, a primitive roundworm made up of a few thousand cells, does something that looks an awful lot like it. Sleep is an ancient, universal experience.

But partly because it is so commonplace, for a long time sleep was a subject that scientists had not woken up to. It is only in the past half-century or so that it has attracted the attention of dedicated researchers. A new book from Kenneth Miller, a science journalist, sets out to chronicle the field’s short but fascinating history.