Why do humans and other “smallish animals” sometimes cough while asleep, but they never sneeze? It’s one of several “pressing,” yet unanswered, questions among sleep researchers, said Dr. Fredric Neuman, in a tongue-in-cheek post at his “Fighting Fear” blog in the publication Psychology Today on Sept. 4.
Neuman presents an interesting—if bloody—theory. Being a quiet sleeper may have protected early humans from nighttime predators. Imagine a saber-toothed tiger treading silently through the woods when suddenly he hears an ‘achoo’ from a nearby cave.
While sneezes originate in the nose, and you don’t need your nose in order to breathe, coughing is directly related to breathing and the need to breathe “trumps other considerations,” Neuman wrote. “Therefore, sleeping is no cough preventative.”
The fact that we don’t sneeze while asleep may also explain why we sometimes step outside into bright light and sneeze repeatedly—it’s all those pent up sneezes.
If natural selection weeded out the sneezing sleepers, why didn’t it do the same with snorers?
It could be that snorers tend to be older people who are less likely to reproduce and, thus, are less important to the survival of the species. Thus, noisy, older sleepers probably made many tasty meals for those prowling, hungry saber-toothed tigers.
