Why We Sleep


Several years ago, a friend of mine recommended Matthew Walker's Why We Sleep. My friend pointed out a very curious set of paragraphs in the first chapter that I want to quote below:

Astonishingly, but until very recently, this was reality: doctors and scientists could not give you a consistent or complete answer as to why we sleep. Consider that we have known the functions of the three other basic drives in life—to eat, to drink, and to reproduce—for many tens if not hundreds of years now. Yet the fourth main biological drive, common across the entire animal kingdom—the drive to sleep—has continued to elude science for millennia.

Addressing the question of why we sleep from an evolutionary perspective only compounds the mystery. No matter what vantage point you take, sleep would appear to be the most foolish of biological phenomena. When you are asleep, you cannot gather food. You cannot socialize. You cannot find a mate and reproduce. You cannot nurture or protect your offspring. Worsse still, sleep leaves you vulnerable to predation. Sleep is surely one of the most puzzling of all human behaviors.

On any one of these grounds—never mind all of them in combination—there ought to have been a strong evolutionary pressure to prevent the emergence of sleep or anything remotely like it. As one sleep scientist has said, "If sleep does not serve an absolutely vital function, then it is the biggest mistake the evolutionary process has ever made."

Yet sleep has persisted. Heroically so. Indeed, every species studied to date sleeps. This simple fact establishes that sleep evolved with—or very soon after—life itself on our planet. Moreover, the subsequent perseverance of sleep throughout evolution means there must be tremendous benefits that far outweigh all of the obvious hazards and detriments. Matthew Walker, Why We Sleep.

Matthew Walker makes a fantastic observation in the last quoted paragraph. He identifies that in order for sleep to be so pervasive across the animal kingdom, sleep must have shown up either at the same time as the creation of the animal kingdom, or shortly thereafter.

From a creationist perspective, the mystery of ubiquitous sleep is easily solved. Avian and aquatic life was created on Day 5 (Genesis 1:20-23). Terrestrial life was created on Day 6 (Genesis 1:24-31). At the close of the daylight hours of Day 6, "the heavens and the earth were finished, and all the host of them. And on the seventh day God ended his work which he had made; and he rested on the seventh day from all his work which he had made. And God blessed the seventh day, and sanctified it: because that in it he had rested from all his work which God created and made." (Genesis 2:1-3).

Not only did God rest on the Seventh-day, but God also punctuated each day of creation with a night, a time for animal life to rest from the day.1

Matthew Walker further observes that, despite the evolutionary pressures against it, sleep continues to persist in all animal life. Again, the creationist perspective easily solves the conundrum. Rest in the Bible is frequently a landmark pointing to the faithfulness of God. The weekly Sabbath rest especially highlights God's role as creator. "But the seventh day is the sabbath of the Lord thy God: in it thou shalt not do any work, thou, nor thy son, nor thy daughter, thy manservant, nor thy maidservant, nor thy cattle, nor thy stranger that is within thy gates: For in six days the LORD made heaven and earth, the sea, and all that in them is, and rested the seventh day: wherefore the LORD blessed the sabbath day, and hallowed it." (Exodus 20:10-11).

The ubiquitous need for rest is a benevolent God's autograph on creation. I would venture that if there were no God, and that life originated through millions of years of unguided evolutionary processes, nature would have found a way to overcome sleep. Yet here we are, sleeping today. To me, this is a powerful argument for the existence of a God that provides for us. We do not need to worry about what we will eat, what we will drink, who we will marry, and the things that would threaten our lives. God cares for all these things, and promises to provide for us, which allows us to rest.

Speak thou also unto the children of Israel, saying, Verily my sabbaths ye shall keep: for it is a sign between me and you throughout your generations; that ye may know that I am the Lord that doth sanctify you. Exodus 31:13

Moreover also I gave them my sabbaths, to be a sign between me and them, that they might know that I am the Lord that sanctify them. Ezekiel 20:12

And hallow my sabbaths; and they shall be a sign between me and you, that you may know that I am the Lord your God. Ezekiel 20:20

God has not left us without evidence. While God desires that our relationship be based on faith and trust, He has left us ample evidence in natural creation (e.g., biology), that we can know of His existence and benevolence by human observation of nature.

Because that which may be known of God is manifest in them; for God hath shewed it unto them [all mankind]. For the invisible things of Him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead; so that they are without excuse: Romans 1:19-20


  1. Most animal life is diurnal, but of course the nocturnal life rests during the day.