Sleep Better: What We Can Learn from Our Stone Age Ancestors

We spend around a third of our lives asleep – and yet we know surprisingly little about how our bodies actually want to sleep. Does it really have to be eight hours? Did our ancestors sleep better than we do? And what does evolution tell us about why so many people sleep poorly today?

In fact, research shows that it is not the duration of sleep that has changed the most over the course of human history – but our environment.

Did Stone Age people really sleep better?

If we want to understand how our bodies are meant to sleep, it is worth taking a look at people who still live without electric light and modern sleeping environments.

A study¹ published in the journal Current Biology examined the sleep patterns of three traditional societies: the Hadza in Tanzania, the San in Namibia and the Tsimane in Bolivia. These people live largely without artificial light and are even more attuned to the natural conditions of their environment. The results may come as a surprise to some:

1. Our ancestors did not sleep any longer

The people studied sleep an average of around six to seven hours per night. This is no more than what many people in modern societies sleep today. The widespread belief that people used to sleep significantly longer is not supported by this data.

2. Sleep follows a natural rhythm

Did they go to bed at sunset? Not quite, as on average several hours would pass before they retired for the night. Nevertheless, their sleep was closely linked to the environment:

• In the morning, natural daylight provided a clear signal to wake up.

• During the day, they spent a lot of time outdoors.

• In the evening, the light would automatically dim, preparing the body for the night.

Every day, their bodies received clear signals about when activity and when rest were required.

3. Sleep patterns change with the seasons

The study also showed that people sleep for about an hour longer in winter than in summer. Interestingly, this is mainly because they go to bed earlier during the darker months – not because they stay in bed longer in the mornings. Our bodies are therefore designed to adapt to natural changes in the environment.

4. It is not just light, but also temperature that influences sleep

A particularly fascinating finding: the sleep cycle is not controlled exclusively by light. The researchers observed that sleep duration is closely linked to the night-time cooling of the environment. People sleep during the cooler phase of the night and often wake up when the temperature begins to rise again.

This means that our internal clock is guided not only by whether it is light or dark, but also by changes in our environment.

5. No evidence of ‘split sleep’ or power naps

Some accounts of people in the past claim that they regularly lay awake for several hours at night and took a long break between two sleep phases. The study found no evidence of this. The sleep of indigenous peoples is predominantly continuous. Regular afternoon naps are also very rare.

The most important finding is therefore this: people in the past did not necessarily sleep for longer or in a fundamentally different way, but they slept better because they followed the natural signals from their environment.

The body still carries an ancient clock within it

Our bodies have adapted to this natural rhythm over many thousands of generations. Our internal clock expects clear signals from the environment: brightness during the day, increasing darkness in the evening, and natural changes such as the drop in temperature at night.

The problem is that whilst our genes have hardly changed since the Stone Age, our environment has changed fundamentally. Today, we spend most of the day indoors and often receive significantly less natural daylight than our bodies are originally accustomed to. In the evening, the opposite happens: living rooms are brightly lit, whilst smartphones, tablets and televisions shine light directly into our eyes right up until just before bedtime. As a result, the distinction between day and night becomes blurred for our internal clock.

The body therefore receives conflicting signals. During the day, it often receives too little light to optimally regulate the waking phase. In the evening, on the other hand, it receives too much light to switch to sleep mode in good time. This is precisely why many people find it difficult to feel tired in the evening, even though they feel exhausted at the same time.

The best sleep habits: What we can learn from our ancestors

We don’t have to live like our ancestors to sleep better. But there is one important thing we can learn from them: our bodies function best when they receive clear signals distinguishing day from night.

1. Soak up the light in the morning

The strongest signal for our internal clock is natural daylight. In the morning in particular, light helps to synchronise the day-night rhythm and signals to the body: ‘Now the active phase begins.’ Even a short spell outdoors is significantly more effective than light coming through windows or artificial indoor lighting.

2. Allow darkness in the evening

After sunset, our ancestors automatically found themselves in a darker environment. Today, we often artificially extend the day. So, in the evening, dim the lights and, especially in the hour before going to bed, reduce bright screen light.

3. Stick to a regular routine

The body’s internal clock thrives on predictability. If you get up and go to bed at completely different times every day, you send your body conflicting signals – much like experiencing a mild case of jet lag. A rhythm that is as consistent as possible helps the body’s biological clock.

4. Be active during the day and go outside

Daylight and exercise work together as powerful timekeepers. Getting plenty of light and activity during the day not only promotes alertness, but also creates better conditions for the night.

5. Creating a mindful sleeping environment

A relatively cool sleeping environment and a natural drop in temperature in the evening send the body signals that it recognises from its evolutionary history.

Conclusion

We don’t need to go back to the Stone Age. But it does show us what our bodies have been adapted to for thousands of years: a natural cycle of light, activity and darkness. Our bodies still function today according to the same basic biological principles as they did thousands of years ago.

Give your natural rhythm a chance and try out these tips in your everyday life.