Sleepy heads

Why do people sleep? And other unanswered questions

A new book, “Mapping the Darkness”, explores the active world of sleep research

Mapping the Darkness. By Kenneth Miller. Hachette Books; 432 pages; $32.50. Oneworld Publications; £18.99

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…