“…human vanity cherishes the absurd notion that our species is the final goal of evolution.”
Richard Dawkins, The Blind Watchmaker (1986)
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Sleep was a mystery to our distant ancestors. This is understandable. After all, until the nineteenth century, we knew very little about the brain. The sleep world you suddenly disappeared into every night had to be something supernatural. Some of this magic has disappeared with greater insight into the workings of our brain, but despite this, there are still many unanswered questions.
The way primordial humans slept may fit our current times better than you might expect. If we want to comprehend our own sleep, we need to look at the way our bodies have evolved over many thousands of years. Modern humans, Homo sapiens, evolved from older lineages between 230,000 and 300,000 years ago.
That is very long ago, especially considering the fact that humans have only been living in cities for less than 10,000 years, that widespread use of electricity dates from the late nineteenth century, and that we have only had computers at home since the late 1970s. Our brains have had to adapt very much to these developments in a relatively short time. Our living conditions have changed dramatically, but the evolution of our bodies and minds is not moving as fast.
If we want to comprehend our own sleep, we need to look at the way our bodies have evolved over many thousands of years.In the field of sleep studies, learning from history is also interesting. Interpreting archaeological finds and observing contemporary hunter-gatherer societies helps us understand how primordial humans slept. Although details on the circadian rhythm (the physical, mental and behavioral changes an organism experiences over a 24-hour cycle) of our ancestors cannot be gleaned through archaeological findings, researchers have studied the lives of contemporary hunter-gatherers to get an idea of our day and night rhythms in the distant past. This has received some criticism, for example from Matthew Wolf-Meyer, anthropology professor at Rensselaer Polytechnic Institute, New York State. He states that because of modern social influences and other factors, no contemporary group can precisely be compared to people from an earlier evolutionary period. On the other hand, in his 2010 monograph The Hadza: Hunter-Gatherers of Tanzania, Frank Marlowe, another professor of anthropology, while accepting that the Hadza are not “living fossils,” says it is amazing that they have preserved so much of their ancestral ways of life, with little changing since they were first officially described in 1911.
The closest, therefore, we can get to getting a glimpse of sleep in the past is by studying a group with living conditions and a lifestyle that is far less influenced by modern-day technology, artificial lighting, and temperature regulation than our own. These circumstances are much more comparable to those in which primordial humans lived.
Bunk beds
The prehistoric period, by definition, is the period from which no “legible” written sources exist. In other words, the historical record seems as illegible as my own prehistoric handwriting. The prehistoric period began 3-5 million years ago and ended around 3300 BCE. When you think of that period, an image of a cave dweller may come to mind—a man holding a club in his hand, trying to fend off a saber-toothed tiger. At least, that is the first thing that comes to my mind. When I see pictures of a prehistoric human, I always get the feeling that the artist must have hated prehistoric people and thought little of their intelligence. The cave dwellers often look somewhat silly, making it almost impossible to imagine that they discovered fire or invented the wheel. I personally think primal humans were much smarter than these depictions.
Primal humans lived as hunter-gatherers, usually traveling from place to place. They lived in groups and hunted wild animals. They also collected things like nuts, seeds, plants, material for clothing, and wood for making fires. Today you go to the store for vegetables or a piece of meat, and on a lazy day you can have a ready-made meal delivered to your home. In prehistoric times, people of course had no access to such luxuries. After a day of hunting and gathering, it was important to rest well.
So, what did the “bedroom” look like in prehistoric times? Although primordial man slept on the ground, it was not always that way. Their ancestors resided in nests in trees. There was an obvious reason for this. High up in the trees, they were protected from predators. One sleep phenomenon in modern man may be a relic of those times. You may recognize it: you are nodding off and suddenly you are jolted awake with a falling sensation. Immediately you are awake! Pretty embarrassing when you are in class, an important but boring meeting, or on the train. We also call those muscle contractions hypnic jerks. Why does this phenomenon occur? It was probably important for survival. After all, if you are a tree-nesting inhabitant who falls asleep in an unfavorable place at high altitude, you could easily drop out of a jungle tree. As your body’s muscles contract for a moment, you are startled awake and are able to check that you are in a safe place.
From the time primitive humans started using fire, it became less necessary to spend our nights in trees, as lighting campfires at night kept predators at bay. There was a significant advantage to sleeping on the ground. Primal man got a more stable night’s rest than in the dangerous heights, which probably led to deeper and less interrupted slumber. That improvement had a positive effect on the brain in general. Our current cognitive intelligence might even be the result of the transition from tree sleep to ground sleep.
The earliest bed that has been discovered dates from around 200,000 years ago. What did it look like? Well, it was of course not a box spring with padded headboard and lovely quilt. It was rather less comfortable and consisted of grass, branches and leaves, and it was located in a cave. You might think that such a place was no fun to doze off in at all, but there is more. Next to the influence of changing weather circumstances, strong variations in temperature and the possible presence of dangers, insects terrorized primal man at night. How do we know? Insect-repellent plants covered the prehistoric bed! If you are an artist who portrays our primeval relatives, if you happen to read this, and if you then decide to draw a primeval man with a silly look in his eyes, I demand that you erase your drawing immediately! They were actually very resourceful types, our ancestors. That insecticide, by the way, was not the only extraordinary finding. Archaeologists found ashes in the various layers of the bed. Primal humans had rather unconventional methods of changing their beds and chasing away insects. They regularly set fire to their beds after sleeping on them. This probably had an effect not only on the creatures that were already crawling around in their bed, but also on any new intruders. Most crawling insects cannot move properly through fine powder because it blocks their breathing and causes dehydration. (I can totally see how the bed-burning ritual would translate to our present day. Imagine if everyone set fire to their bed after sleeping in it once. Then every morning you’d be standing with your trailer at the dump with rows of cars behind you.
It’s a good thing we have other ways of changing our beds these days. We have washing machines now and our beds thankfully no longer smell of burnt branches, but of wild honey or fresh lavender.)
Interestingly, primal humans also had other uses for their beds than dozing off on them. The bed was also a workplace for manufacturing stone tools used for hunting, for cleaning animal hides, and for food preparation. We can deduce this from stone shards found at the sleeping place. Imagine sawing through a series of wooden planks on a newly made bed and then trying to fall asleep in between the sawdust and tools. Say goodbye to a nice night’s rest! In addition to stone shards, grains of red and orange ochre covered the beds. Primal man probably used these for decorating their bodies or for coloring objects.
Did cave dwellers simply have sex in their beds? We do not know exactly, but to answer these questions, researchers have studied the habits of modern hunter-gatherers, whose living conditions have remained pretty much the same for thousands of years. The Aka tribe was one of the groups in which sexual activity was examined. They live in the tropical forest region of the Central African Republic. The Aka are primarily net-hunting foragers who don’t live in caves, but in camps on the ground. The studies show that while some men are polygamous, the vast majority are monogamous. Because in modern hunter-gatherers polygamy is only seen in a very small part of the population, it is likely that sex in prehistoric peoples was between two steady partners.
Sexual activity in most tribes, such as the Aka, is typically covert. This means that the place where people sleep in groups is not the same as the place where they would have sex, because other tribe members would see the lovers in the act. For example, some of the Aka foragers in the study explained that they had sex in the forest, away from the rest of the tribe, while others had sex in their huts. A reason for not having sex in the open might be to reduce shame, but also jealousy and mating competition. From research into contemporary tribes such as the Aka, we might conclude that prehistoric peoples used their beds for rest and for work but less commonly for sex.
Sleep, eat, move, repeat
Prehistoric man is regularly an inspiration for new insights into health and wellness. One well-known example is the “Paleolithic diet.” Primal man is thought to have lived on a range of meat, fish, vegetables, fruits and nuts; according to the adherents of the Paleo diet, these are still the best sources of nutrition for modern man. There are, of course, proponents and opponents, but there is evidence that certain tenets of the Paleo diet constitute sound nutritional advice. How did this primordial diet influence sleep?
Hundreds of thousands of years ago, humans learned how to cook with fire. They began to use stone tools for different purposes and to access food more easily. Researchers such as anthropologist Katharine Milton suggest that primitive man ate both vegetables and meat; others claim that more vegetables were eaten than lean meat, and others that fish was the most important staple. Modern hunter-gatherer tribes now generally eat around 30 per cent animal-based food and 70 per cent vegetables (in extremely cold areas, such as the Arctic, however, they feed almost exclusively on animals).
Around 10,000 years ago, our diet started to change. It was the beginning of the agricultural era and people began to eat more grains, legumes, dairy products and vegetable oils. In the modern era, another big transition to other food resources occurred. The industrial period that started around 1760 brought in more efficient farming methods, increased access to certain food sources, and ultimately opened the way to new food preservation techniques, with products such as canned meats, condensed soup and white bread becoming available.
In 2003, anthropologist Clark Spencer Larsen from the Ohio State University in Columbus claimed that the transition from our Paleolithic diet to the diet of the agricultural era led to a mismatch between our bodies’ needs and the type of food we ate. Evidence for this hypothesis comes from research that suggests that hunter-gatherers had a lower risk of age-related and chronic disease than agricultural workers. Possibly this has to do with the fact that people in the agricultural period started to eat a smaller range of food types, which contained fewer absorbable nutrients.
Critics state that this effect had more to do with the fact that prehistoric hunter-gatherers perished early, so they did not reach an age in which chronic disease would develop. Evidence for the exact state of health of prehistoric humans is scarce. However, we can compare modern hunter-gatherers with people from industrialized societies. Research shows that when comparing young hunter-gatherers with young people from industrialized countries, the former show lower rates of obesity, hypertension and insulin resistance. It might have to do with the combination of food that is more compatible with our Paleolithic DNA but also with the hunter-gatherers’ activity levels, which are often much higher than those of populations in industrialized societies.
My image of cave dwellers changed a little…somehow it was a relief that they might have not been that different from modern humans after all.So, if there were health benefits of the Paleolithic diet, how could it have influenced the way people sleep? One of the characteristics of the diet is that it is high in protein, which might have had a positive influence on the cave dwellers’ night’s rest. More specifically, high-protein meals such as in the Paleo diet show good effects on sleep, while poor sleepers get their energy more from carbohydrates and fats. In addition, the original Paleolithic diet contained relatively few sugars, and scientific research shows that low-sugar diets might still have a positive effect on sleep in modern humans.
Contemporary hunter-gatherers have a very different activity pattern compared to people in industrialized societies: on average, males take between 18-19,000 steps per day and females around 11,000 steps. In contrast, in the United States, the average adult takes around 5,000 steps per day—a big difference from how it used to be.
From this, we might conclude that primordial man was way more active than we are nowadays, which must have had a positive effect on overall health and sleep. Research suggests that low levels of physical activity are another evolutionary mismatch: in other words, we are moving too little to stay healthy, but that is not completely new! In 2021, Daniel Lieberman and colleagues stated that people who were more active in the prehistoric age survived better through the evolutional process of natural selection because they were better able to provide for and take care of offspring. This in turn led to the selection of people who were better able to repair and maintain the body after physical activity, which might have decreased their risk of chronic disease. The “active grandparent hypothesis” is another term for this theory. Put differently, trying to find more food led to more exercise, which led to greater need for recovery, which promoted sleep.
Nowadays access to food is easy for most people and we have all the resources within reach. The result is that there is less need for physical activity for direct survival, leading to an increase of inactivity. This inactivity can result in less need for recovery and for sleep. Our current lifestyles probably do not promote health and sleep as much as those we once had.
In short, living in the prehistoric age was probably more in line with the health needs and sleep needs of our bodies. Cave dwellers had to move more because they had to hunt for food and constantly find new food resources. Additionally, what they ate was better for sleep than many of the processed and sugar-rich foods we eat nowadays.
This almost sounds as if we all have to live like cave dwellers again because they had such positive health-promoting behavior. However, research shows that they sometimes also indulged in unhealthy behaviors. I was quite surprised to find that they drank alcohol, and used nicotine and other stimulants. The earliest evidence of the use of nicotine dates from more than 12,000 years ago. Excavations at the Wishbone site in Salt Lake Desert in Utah exposed charred seeds of a tobacco plant in a small fireplace. It is unclear exactly how the hunter-gatherers used the plant material. Perhaps they smoked tobacco, but it might also be that they chewed it then spat it out. It seems that the cave dwellers also drank a kind of primordial wine. Cave archaeologists found alcohol in storage jars in an excavation site in China. In Henan province, a beverage of rice, honey and fruit dates from 7,000 BCE. These drinks were likely of social, religious and medical significance.
A few millennia later, around 5,000 years ago, there was already beer in China. Archaeologists analyzing pottery vessels found evidence of ingredients such as barley and broomcorn millet. This indicates that the people of ancient China not only brewed beer, but also used specialized tools for the task. In addition, research shows that cave dwellers would have sometimes been high on drugs. Analysis of Bronze Age human hair found on the island of Menorca shows that they used the alkaloids ephedrine, atropine and scopolamine. These psychoactive substances can induce realistic hallucinations, disorientation and alteration of sensorial perception, and were probably used to help people reach other states of mind, connecting them differently or more intensely to nature, each other, or gods in ritual ceremonies.
I must say my image of cave dwellers changed a little after examining this research; somehow it was a relief that they might have not been that different from modern humans after all. Of course, the use of alcohol, alkaloid-bearing plants and nicotine would not have been very sleep-promoting, but they must have had many other things on their minds than trying to sleep well—maybe they did not even really try, because probably lying awake was not really something to worry about. In fact, modern hunter-gatherers do not even have a word for bad sleep, because they usually do not perceive a sleep problem as we would.
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From How to Sleep Like a Caveman: Ancient Wisdom for a Better Night’s Rest by Dr. Merijn van de Laar. Copyright © 2025 by Merijn van de Laar. Adapted with permission of Mariner Books, a division of HarperCollins Publishers.
