The Evolution of Human Sleep

Human sleep didn’t evolve around an 8-hour schedule.

Our early ancestors likely slept differently than we do today. As humans transitioned from sleeping in trees to sleeping safely on the ground around social groups and campfires, deeper and more REM-rich sleep emerged, supporting memory, learning, creativity, and problem-solving.

For much of history, people practiced “first sleep” and “second sleep,” waking naturally during the night before returning to rest. Historical accounts suggest this pattern was once considered completely normal.

Industrialization Changed Everything

The modern concept of a continuous 8-hour sleep period is relatively new. The Industrial Revolution, artificial lighting, and factory work schedules extended waking hours and gradually disconnected people from natural light-dark cycles.

The clock began to dictate sleep patterns more than the rising and setting of the sun, fundamentally changing how humans slept.

The Modern Evolutionary Mismatch

Our biology has changed very little over the past few thousand years, but our environment has changed dramatically. Human circadian rhythms remain deeply connected to daylight, darkness, movement, food availability, and seasonal changes. Yet many people now spend their days indoors and their evenings exposed to artificial light, screens, ultra-processed foods, chronic stress, and sedentary lifestyles.

Many of today’s sleep challenges may be the result of an evolutionary mismatch between ancient biology and modern living.

The Takeaway: Biology First

If you want better sleep, start by aligning your lifestyle with human biology:

• Get outside and expose your eyes to natural morning light within the first hour of waking.

• Move your body daily. Walking, strength training, and physical activity help regulate circadian rhythms and improve sleep quality.

• Prioritize nutrient-dense whole foods and avoid heavy meals, excess alcohol, and ultra-processed foods late in the evening.

• Stay hydrated throughout the day.

• Reduce artificial light exposure after sunset, especially from phones, tablets, and televisions.

• Maintain consistent sleep and wake times whenever possible.

• Keep your bedroom as dark as possible. Human eyelids are surprisingly thin and can transmit up to 5% of ambient light, enough to suppress melatonin production, disrupt circadian rhythms, and interfere with deep, restorative sleep. Darkness is a biological signal that tells the brain it is time to recover.

Sleep is not a standalone behavior. It is the result of how we eat, move, recover, and interact with our environment throughout the day.

Lifestyle is Medicine. Biology First.

Coach Gerald J Joseph
Coach Brittany L Wilson