Daytime Sleep: Why Humans Avoid Napping In The Sun

Sleep is a vital process that accounts for one-third of the average human lifespan. Despite this, the biological purpose of sleep remains a mystery. However, it is known that sleep is essential for the proper functioning of the brain and body, with a lack of sleep leading to impaired concentration, memory, and emotional regulation.

The human sleep cycle is regulated by two main processes: circadian rhythms and the sleep drive. Circadian rhythms are 24-hour cycles that are controlled by a biological clock in the brain, which responds to light cues and regulates the production of the hormone melatonin. The sleep drive, on the other hand, is the body's desire for sleep, which intensifies the longer one stays awake.

This paragraph introduces the topic of why humans don't sleep during the day, highlighting the importance of sleep and providing an overview of the biological processes that regulate the sleep cycle.

Humans are predators, not prey

Our vision is pretty good compared to most animals, especially our depth perception, which is a result of our ancestors' tree-dwelling habits. We also have a good sense of balance and proprioception, as well as touch sensitivity, particularly at the tips of our fingers.

However, our eyes are not well-adapted for night vision. We are crepuscular, like orangutans, and our biology is geared towards being active in the morning and evening, with a rest or nap in the middle of the day. Our eyes are well-adapted to delineating color when there is sufficient light, which is useful for scavenging.

Humans are also social and cooperative. We live in large groups and protect each other. We are also intelligent and have been using tools for millions of years. We set traps and hunt in groups, which makes us very successful predators.

Our sleep patterns are regulated by our circadian rhythms, which are controlled by a biological clock located in the brain. This clock responds to light cues, increasing the production of the hormone melatonin at night, and switching it off when it senses light. This is why people with total blindness often have trouble sleeping.

The two main processes that regulate sleep are circadian rhythms and sleep drive. Sleep drive is like hunger—the longer you are awake, the more your body craves sleep. However, unlike with hunger, when your body is exhausted, it can put you to sleep even if you are in a meeting or behind the wheel of a car.

In addition to helping our bodies recover and heal, sleep is vital for brain function. A healthy amount of sleep is necessary for "brain plasticity," or the brain's ability to adapt to new input. Without enough sleep, we become unable to process and remember what we have learned during the day. Sleep may also promote the removal of waste products from brain cells, which seems to occur less efficiently when the brain is awake.

In conclusion, while humans are not prey, our sleep patterns and daily activities are influenced by our biology, specifically our circadian rhythms and sleep drive, as well as our need to recover, heal, and maintain proper brain function.

Our vision is pretty good compared to most animals

Humans are diurnal, meaning they are active during the day and sleep at night. This is partly due to our visual system, which is less well-adapted for night vision compared to nocturnal animals. However, human vision is pretty good compared to most animals.

The human eye is one of the most complex structures in nature. It can take in a million simultaneous impressions and differentiate between eight million colours. On a clear, moonless night, a human can detect a match being struck 50 miles away. While some animals, such as eagles, have sharper eyesight, and others, such as cats, have superior night vision, humans have excellent depth perception. This is likely due to our ancestors' arboreal lifestyle, which involved climbing trees and throwing objects.

In addition to depth perception, humans have good balance and proprioception, which are also linked to our ancestors' tree-dwelling habits. We also have sensitive touch, especially at our fingertips. These factors, along with our visual system, contribute to our overall sense perception, which is quite strong compared to other animals.

Our visual system is particularly important to our daily lives, as we rely heavily on our sense of sight. This is one reason why we are diurnal; we are most active during the time when we can see best. Being active during the day also aligns with our need to gather food, which is more easily accomplished with sufficient light.

While humans are well-adapted to a diurnal lifestyle, there is still variation within our species. Some individuals are "night owls", preferring to be active in the evening or at night. Additionally, humans have the ability to adapt their sleep patterns to their circumstances. For example, people can work night shifts or take naps during the day if needed. Ultimately, our sleep patterns are influenced by both our biological makeup and our social and environmental factors.

We rely heavily on our sense of vision

Humans are heavily reliant on their sense of vision, which is far more effective during the day than at night. This is due to our eyes not being well-adapted for night vision, unlike nocturnal animals. However, human vision is adept at delineating colour when there is sufficient light, which is useful for scavenging.

Human vision is also excellent at perceiving depth, which is a skill that makes sense given our ancestors' propensity for climbing trees and throwing objects. This depth perception is a key factor in our ability to hunt and gather.

Our sense of vision is so important that our brains devote a significant amount of resources to it, even during sleep. The thalamus, for example, sends and receives information from the senses to the cerebral cortex. During REM sleep, the thalamus remains active, sending the cortex images, sounds, and other sensations that fill our dreams.

The human brain is also highly active during sleep, reorganising and cataloguing memories and learned information. This process is akin to a librarian sorting and shelving books at the end of the day, making it easier to access and use learned information.

In addition to our reliance on vision, humans are also a diurnal species, meaning we are naturally active during the day and sleep at night. This is due to our evolutionary history, as sleeping at night allowed early humans to simultaneously avoid predators, conserve energy, and meet their need for rest.

Overall, our strong dependence on vision, coupled with our diurnal nature, means that we are most active during the day when our sense of sight is most effective.

Our bodies crave sleep like they hunger for food

Sleep is an essential part of our daily routine, with humans spending about a third of their lives asleep. Our bodies crave sleep, much like they hunger for food. Throughout the day, our desire for sleep builds, and when it reaches a certain point, we need to sleep.

This is because sleep is vital for our bodies and minds to recharge, allowing us to feel refreshed and alert when we wake up. It helps the body remain healthy and fight off diseases. Without enough sleep, our brains cannot function properly, impairing our ability to concentrate, think clearly, and process memories.

Sleep also plays a crucial role in various physical and psychological functions. It helps with learning and memory consolidation, emotional regulation, judgment and decision-making, problem-solving, energy conservation, growth and healing, and immunity.

The biological patterns that enable humans to live according to the 24-hour day-night cycle are called circadian rhythms. These rhythms work alongside the sleep drive, which is our desire for sleep that intensifies the longer we stay awake. Circadian rhythms, including the sleep-wake cycle, are influenced by environmental cues, such as light and darkness.

During sleep, our bodies "power down," and most body systems, including the brain, become less active. This reduced activity allows our bodies to heal injuries and repair any issues that occurred during the day. Sleep also enables the brain to reorganize and catalog memories and learned information, making it easier to access and retrieve them.

In summary, our bodies crave sleep like they hunger for food because sleep is essential for our physical and mental well-being. It helps us maintain optimal health, enhances our cognitive abilities, and ensures we have the energy needed to function effectively throughout the day.

Our genes may play a role in our sleep patterns

Our genes may play a significant role in influencing our sleep patterns and determining how much sleep we need. Scientists have identified several genes involved with sleep and sleep disorders, including genes that control the activity of neurons, and "clock" genes such as Per, tim, and Cry, which influence our circadian rhythms and the timing of sleep.

For instance, Johns Hopkins sleep expert and neurologist Mark Wu, M.D., Ph.D., and his team recently identified a gene involved in the circadian regulation of sleep timing. They found that when this gene, called "wide awake," was removed from fruit flies, the flies experienced difficulties falling and staying asleep. A similar sleep gene exists in both humans and mice, and scientists are continuing to study it to better understand how processes within our cells impact our ability to sleep.

Additionally, some people may inherit the trait of being a "short sleeper" from a parent, indicating that variations in sleep requirements could be genetic. Further research will help provide a clearer understanding of inherited sleep patterns and the risks of circadian and sleep disorders.

Frequently asked questions