I just finished reading the non-fiction book THE SIESTA AND THE MIDNIGHT SUN. Author Jessa Gamble sent me a copy because she had interviewed me for the book in connection with BEGGARS IN SPAIN. This is not, however, a book about SF; it's a well-written overview of the research connected with circadian rhythms, including sleep. Since I researched BEGGARS 20 years ago (and where does`all that time go?), much more has been discovered about sleep. Not, however, why we must do it. That remains unanswered.
The book is full of fascinating information about how all living things are governed by circadian rhythms, even in the absence of the light that triggers such rhythms in nature. Much of Gamble's research was carried out above the Arctic Circle, where night lasts six months. Humans often have a very hard time with this, unless genetically adapted to it over millennia (as the Inuit are, for instance). Some of the interesting things I learned about circadian rhythms:
If you remove crabs far from the ocean and put them in pens with sloping floors, they will still move up and down the slopes according to the tides on their home beach.
Cell division is circadian, even the out-of-control division of cancer cells. Certain lymphomas divide their cells between 9:00 and 10:00 at night. In contrast, the cells of the gut lining divide twenty-three times as much at 7:00 a.m. than they do in the evening. These sorts of finding have implications for the new field of chronotherapy: timing medical tests and treatment to take advantage of circadian rhythms. The book says that a British study showed that colon-cancer patients could tolerate up to 40% greater dosage of meds using chronotherapy -- and with fewer side effects.
People cannot last for more than a month or so on polyphasic sleep, which involves only short naps spread throughout 24 hours. But they do very well with biphasic sleep: a longish sleep starting late at night and a siesta in the afternoon. This was a successful program for traditional Mediterranean societies, plus Winston Churchill.
Herbivores sleep less than carnivores, which explains my dog.
I thoroughly enjoyed this book. Also -- I feel another story coming on.