In recent decades researchers have discovered a great deal about the various stages of sleep and especially about the extraordinary and subtle physiological changes that accompany them. REM sleep, for example, also called dreaming sleep, is manifested by the paralysis of all the voluntary muscles in the body with the exception of the eye muscles and those that control breathing. Obvious signs of sexual arousal also occur during REM sleep. The importance of sleep to memory and to appetite control has been uncovered. However, sleep researchers are still haunted by three difficult questions:
A possible answer: There is an obvious survival benefit for human beings and other smallish animals to make as little noise as possible when sleeping. (Imagine a saber-tooth tiger treading silently through the woods when suddenly he hears a sneeze from a nearby cave.) Therefore, these creatures do not sneeze while sleeping. So, how come they can cough, sometimes waking themselves up? (I have seen this myself.) I have a theory to propose: The nose is the seat of the sneeze; and you don’t have to breathe through the nose. But you still have to breathe. Breathing is very important and trumps other considerations.
In other words: In many conditions (bronchitis, pneumonia, aspiration, drowning, etc.) coughing is more urgent, and more important for survival, than the need to avoid attracting the attention of a saber-toothed tiger that might be strolling by, especially since there are no longer any saber-toothed tigers around. (I do not think drowning while asleep, however, was much more of a threat back then, than it is now, unless one were to fall asleep in the bathtub; and, of course, there were no bathtubs in those days.) In these circumstances, and others, coughing is important, whether or not you are asleep. Sneezing, however, which is a function of some trouble in the nose, can be suppressed safely. (Although sometimes with difficult by certain individuals who are capable of a string of sneezes when sitting in a classroom.) I think the fact that some people sneeze when exiting a dark place, such as a cave, into the sunlight is explained by similar torturous reasoning: (all that pent-up sneezing from not sneezing while asleep.)
Snoring, which is just as noisy as sneezing, tends to appear as people get older, when they are less likely to reproduce. Therefore, their survival is less important for the course of evolution. (Not to put too fine a point on it, if a saber-toothed tiger ate a noisy, but elderly person, there would not be too much of a loss.)
The answer, I think, may have to do with sex. With the exception of certain eccentric individuals, most people have sex in a more or less flat state (prone or supine, usually one prone and the other supine)—as opposed to horses who have sex standing up. Not by coincidence, horses also sleep standing up. (Other creatures such as fish can have sex at a distance, in any old position, as long as they are more or less in the same neighborhood.)
Human beings tend to have sex directly before or directly after sleeping. Therefore, since sex is a more or less horizontal affair, so is sleep. Sex is very important. After survival, sex is the next most important thing.
Sex and sleep as a communal affair
Unlike other animals, even some pack animals, human beings have evolved to spend a lot of time with each other. In contrast, look at lions. The females hang out together, but the males head off by themselves to do whatever it is they need to do. They have no interest in exclusively male activities, like humans do with their sports leagues and all night poker games. In prehistoric times, there was a survival advantage for human beings to do things in a group. There was even an advantage in all the females giving birth at the same time. For that reason women who live together (think dormitory or cave) tend to menstruate (and ovulate) at the same time. This is because of how they smell. (In no sense am I speaking in derogatory terms.) Women somehow pick up olfactory clues as to when they are supposed to menstruate. I think they should be congratulated rather than denigrated for smelling in such a incisive manner. (I am using the word “smell” in both senses of the word.)
Because of the presence of saber-toothed tigers, there was in prehistoric times an advantage in everyone going to sleep at the same time. Even those formidable creatures hesitated to attack a whole community of human beings bunched together in a cave and making noises and throwing rocks.) Therefore, in those many years before speech evolved, there had to be a signal that it was time to go to bed. This was yawning. (In those days before speech, human beings communicated with guttural sounds and gestures, such as sticking out their tongues and wagging their fingers in their ears, or spitting.) This is the reason why yawning is contagious. The head guys would yawn, and then everyone else would yawn and know that it was bedtime. Sex in those days was like a big party. Couples having sex privately were considered weird and such delicacy did not become fashionable for another hundred thousand years, when huts and walls were invented.
It is known that among fire-fighters there is a high percentage of bed-wetters. (I mean former bed-wetters. Most bed-wetters are children, although I know one man who did not stop until his wedding night. Which makes you stop and think, doesn’t it?) Some theorists have opined that bed-wetting might have been an early adaptation to out of control fires back when they all lived in a cave. I think this is absurd. You would have to be sleeping in the middle of the fire for bed-wetting to have any effect. Still, the association seems to be real. This kind of fact is mother’s milk to psychoanalysts and their ilk. They could write a whole library on this sort of thing; and probably they should. It would get their minds off all the problems associated with toilet training. (For more about bed-wetting in the military, see my novel “Maneuvers.”)
If the association between fire-fighting and enuresis has persisted until the present time, it suggests that there is a fire-fighting/enuresis gene, which would explain why so many firemen have followed their fathers into the profession. There may be hidden evidence for a caste of fire-fighters, similar to the “Cohens,” who were the male descendants of Aaron and who were hereditary Hebrew priests. (Actually, there are no longer any Hebrew priests, and yet there are still a lot of “Cohens,” which suggests that fire-fighting might be a more stable business.)(I think I may be getting a little mixed-up here.)
In any case, these are the troubling thoughts that keep sleep-researchers up at night.(c) Fredric Neuman 2013 FollowDr. Neuman's blog at fredricneumanmd.com/blog