As I asked in a post yesterday, why do we sleep? Researchers have posited several hypotheses for the function of sleep, one of which focuses on sleep as a process of restoration.

The restorative theory states that sleep allows for the body to repair and [replenish] cellular components necessary for biological functions that become depleted throughout an awake day. This is backed by the finding that many functions in the body, such as muscle repair, tissue growth, protein synthesis, and release of many of the important hormones for growth, occur primarily during sleep.¹

Although cellular repair appears to be part of the purpose of sleep, much attention has focused on the various stages of sleep and brain activity, differentiated by their EEG signatures.  A brief description of rapid eye movement (REM) sleep and the deepest of three non-REM stages (N3) is given below.

N3 is also known as slow-wave sleep (SWS). This is considered the deepest stage of sleep…. This is the stage when the body repairs and regrows tissues, builds bone and muscle and strengthens the immune system.

REM is associated with dreaming and is not considered a restful sleep stage. While the EEG [electroencephalogram] is similar to an awake individual, the skeletal muscles are atonic and without movement, except for the eyes and diaphragmatic breathing muscles, which remain active…. The brain is highly active throughout REM sleep, increasing brain metabolism by up to 20%…. Dreams occur during the REM phase of the sleep cycle, in which the body is fully paralyzed.²

Sleep — Not Optional

Weary with toil, I haste me to my bed, / The dear repose for limbs with travel tired.³

Although current understanding of our need for sleep is incomplete, one thing is certain: sleep is not optional. Sleep deprivation results in physical, neurological, and emotional degradations.

Lack of sleep affects our memory and ability to think clearly, and sleep deprivation can lead to neurological dysfunction such as mood swings and hallucinations. Those who do not get enough sleep are at higher risk of developing obesity, [diabetes mellitus], and cardiovascular disease.⁴

With evolutionary assumptions leaving researchers perplexed as to how “sleep evolved,” one scientist has decided to punt the issue and invert the paradigm, suggesting that sleep just happens, but that evolution was necessary to bring about wakefulness.

“I think if it’s alive, it sleeps,” says Paul Shaw, a neuroscientist from Washington University in St. Louis. The earliest life forms were unresponsive until they evolved ways to react to their environment, he suggests, and sleep is a return to the default state. “I think we didn’t evolve sleep, we evolved wakefulness.”⁵

However, if the coordinated physiological and neurological processes necessary to produce sleep seem daunting for natural processes to originate without a Designer, then producing wakefulness, aka consciousness, with its attendant qualities of mind, is completely beyond the reach of any Darwinian mechanism.

Sleep Design

From the perspective of intelligent design, sleep should be associated with at least two levels of design. One is seen in the multiple physiological regulatory networks that transition us from wakefulness to sleep and then return us to wakefulness. The second facet of design would be the connection between sleep and human flourishing. 

Imagine a world without sleep. Predatory animals, such as lions and cheetahs, that normally sleep 12 to 13 hours per day would continually pose a threat, never going “off duty.” For creatures not designed to thrive at night, about half of their existence, while darkness prevails, would produce frustration, confusion, boredom, and peril. 

Newborn infants sleep for up to 16 to 18 hours a day, discontinuously,⁶ during the first two months of their lives. Toddlers sleep 11 to 14 hours per day and take one or two naps per day of 1 to 3 hours. Mothers of newborns would succumb to exhaustion if their children never slept.

Sleep as part of a purposeful design may serve us in multiple additional ways. Sleep provides an extended period of rest for the weary. It gives a respite from emotional and physical pain. It gives our brains a chance to process stimuli, information, and experiences. It saves us from possible boredom during the nighttime periods of darkness — especially in human history prior to the development of electric lighting and technology-based entertainment. Sleep allows us a “time-out” from emotional and social conflicts with family members. It also sets a limit to the amount of harm evil people can perpetrate. 

Sleep seems to be essential for the long-term well-being of all creatures. Animals (including humans) can typically survive longer without any food than without any sleep.⁷

Why is sleeping, in which the conscious mind/brain is asleep, categorically more restful and recuperative to the body than merely lying down and maintaining a state of physical inactivity? One could almost conclude that the way a conscious mind/brain thinks and how it responds to external stimuli is inimical to the sustained well-being of a physical body. Sleep gives respite to the body against the demands of the ever-vigilant mind/brain. This is especially true when the mind/brain is stimulated by thoughts due to fear, anger, jealousy, or other stress-producing emotions.

A tranquil mind gives life to the flesh, but passion makes the bones rot.⁸

Our brains and nervous systems are seldom “tranquil” enough to avoid stressing our bodies and minds. But even with a low-stress lifestyle, regular periods of sleep in which our bodies are relieved of stimuli generated by the brain and nervous system are needed to avoid exhaustion. Sleep seems to be a gift that allows us to live conscious lives in a physical body.

It’s remarkable that we regularly place our consciousness on pause, become nearly insensible to external sensory input, and eventually enter a state of total bodily paralysis. Still more amazing is our daily recovery from such a state. Our utter dependence upon entering this altered state on a diurnal cycle is also perplexing from an evolutionary perspective. As much as for any aspect of our existence, sleeping and waking point to the reality of a transcendent intelligent designer. As the Psalmist put it,

I lay down and slept; / I woke again, for the Lord sustained me.⁹

Not least of all, our need for sleep, the universal experience of the restorative cycle of sleeping and waking, is a constant reminder to us of our mortal dependence. And our awakening serves as a metaphor for the hope of new birth.

Notes

1. Joshua E. Brinkman, Vamsi Reddy, Sandeep Sharma, “Physiology of Sleep” (April 3, 2023).
2. Aakash K. Pate, Vamsi Reddy, Karlie R. Shumway, John F. Araujo, “Physiology, Sleep Stages” (September 7, 2022).
3. Shakespeare’s Sonnet 27, “10 of the Best Poems about Sleep – Interesting Literature.”
4. Aakash K. Pate, Vamsi Reddy, Karlie R. Shumway, John F. Araujo, “Physiology, Sleep Stages” (September 7, 2022).
5. “The Simplest of Slumbers,” Elizabeth Pennisi, Science.
6. Aakash K. Pate, Vamsi Reddy, Karlie R. Shumway, John F. Araujo, “Physiology, Sleep Stages” (September 7, 2022) .
7. Jacob Empson, Sleep and Dreaming, 3rd ed. (New York: Palgrave Publishers, 2002).
8. Proverbs 14:30, RSV.
9. Psalm 3:5, ESV.