The Evolution of Sleep: Why We Sleep for 8 Hours and Our Ancestors Didn’t
Introduction
So, why do we insist on sleeping for 8 hours when our ancestors didn’t? The concept of sleep has been a subject of extensive research and ongoing debate. Science is continually redefining our understanding of sleep, making it a dynamic and evolving field. This article delves into the historical and biological aspects of sleep, exploring why the human body was initially designed for less sleep and how societal changes have influenced our current sleep patterns.
Why Eight Hours of Sleep?
While the notion of 8 hours of sleep seems like a fixed standard, it is not carved in stone. In reality, the average sleep duration is around 7.5 to 8 hours. However, the requirement for 8 hours of sleep is not universal. Some individuals thrive on less than 7 hours, while others may need more than 8 hours. This variability is reflective of the diverse sleeping patterns observed across different mammals, with some creatures requiring as little as 2 hours of sleep and others up to 20 hours daily.
Evolution of Sleep Patterns
Our ancestors didn’t need 8 hours of sleep, not because there was some special quality in humans but because the environment and lifestyle required less sleep. Early humans spent their days gathering, hunting, and working, often without the luxury of artificial light. It was only with the advent of the industrial revolution that the concept of an 8–9 hour workday emerged, necessitating a consistent 8 hours of sleep.
Some experts believe that the human body evolved to require 8 consecutive hours of sleep, though this is contradicted by historical and contemporary examples. For instance, infants sleep almost the entire day, while teenagers naturally stay up later into the night, often sleeping in during mornings. Even in adulthood, sleep patterns can be highly varied, shifting between longer naps and more fragmented sleep.
The Role of Shifts in Sleep Patterns
People in their late 20s to 50s often experience natural sleep shifts, with 3 to 4 hours of sleep followed by an hour or two awake before sleeping again until sunrise. This pattern also applies to older adults, who often go to bed early and wake up early. Thus, the idea of 8 straight hours of sleep is neither realistic nor natural for any age group.
The amount of sleep appears to vary not just by age but also by season. In mid-latitudes, the duration of nighttime hours can range from about 12 hours in winter to 6 or 7 hours in summer. Generally, humans tend to go to bed about 2 to 3 hours after dark and wake around sunrise, or an hour after. At the equator, the night hours remain constant year-round, often averaging around 7 to 8 hours per night. This suggests that the 7 to 8-hour figure may be a generalized projection from our ancestral times.
Fire and Early Human Behavior
Even before the invention of fire, early humans would naturally stay up for some time after dark, engaging in activities like campfire storytelling, music, and dancing. Evidence suggests that this phenomenon has been occurring for at least one million years, proving that eight hours of sleep is not an insurmountable requirement for human beings.
Conclusion
Understanding our sleep patterns requires delving into the complexities of evolution and modern life. While the average person might still aim for 8 hours of sleep, the actual requirement can vary greatly based on individual needs, environmental factors, and lifestyle choices. The historical and biological evidence shows that the need for 8 hours of sleep is not a universal constant but rather a dynamic evolution influenced by various factors.