The broader issue regarding sleep disruption is identified as sleep fragmentation. We don’t’ just wake up once in the middle of the night; rather, we wake up many times and might even find ourselves sleeping “fitfully.” Our night seems to be an ongoing dance between wakefulness and sleep. This might mean that we are spending most of our night in stage one, stage two and REM sleep. It might also mean that we are spending a large amount of time in the pre-sleep and post-sleep states of sleep limbo that are called hypnagogic (pre) and hypnopompic (post). These intermediate states are often filled with very loose (disorganized) thinking, vague images (such as our legs and feet seemingly to grow larger or smaller, our arms appearing to become numb), and/or a swirling of various feelings.
In general, these fragmented sleep conditions are judged to be negative and quite unhealthy. But this isn’t the conclusions reached by all sleep specialists. Some of these experts point out that deep, uninterrupted sleep was not common among our ancient relatives. When our ancestors were living on the Savannah in Africa, it was important to remain alert to some extent in monitoring one’s environment. So that a great night of sleep is not being interrupted by a lion who is eating us!
We either needed to be aware in some way of the potential dangers surrounding us on the Savannah or we needed to belong to a tribe in which one or more members remained fully awake during portions of the night, serving as watch guards—keeping alert to potential dangers from other tribes or human-eating animals. It is interesting to note that some animals can actually sleep half of their brain, while remaining awake with the other half. Unfortunately, humans have not been blessed with this capacity. Instead, we either need to remain somewhat wakeful or be the member of a well-organized tribe with an effective watch guard system in place.
