A few years ago, a disturbing realization came upon me and it was:
Homo sapiens is the only diurnal species that carries out normal daytime activities after sunset.
The discord created by this realization led me to understanding the health implications of altering our environment to suit our ever-changing comfort levels; and also to making changes in our lives to realign ourselves with natural cycles. In this blog post I will write about this journey. The only environmental factor I take into consideration here is light.
According to archaeological records, Homo sapiens started walking the earth nearly 200,000 years ago. We are still biologically the same as those initial men and women. But ever since the advent of artificial lighting, human race doesn't experience natural light and darkness the way it did for thousands of years.
Thoughts and questions such as these bothered me deeply -- Artificial lighting is hardly a century old technology. What is a century or a few in geological time scales? Not even an insignificant blip! How can our evolutionary needs for light and darkness change in that short amount of time? Won't human body's mechanisms, that have evolved to take in natural light and darkness as their cues, go awry because of our modern ways of living? Natural light and darkness are free for everyone. But still how many actually meet the human body's requirement for these? I moaned for the terrible loss of natural light and darkness from most people's lives.
First, some science: The color components of visible light include violet, blue, green, yellow, orange and red. White light is a mixture of all these lights. So is the visible light component of sunlight. The blue component of the visible light spectrum is known to wake us up and keep us on our toes by secreting a hormone called cortisol. Following the natural cycle of the sun, as the day wanes so should cortisol production. As the sun sets, in response to darkness a hormone called melatonin gets secreted. This hormone plays a key role in regulating our sleep. This beautiful dance between cortisol and melatonin maintains the day-night cycle and circadian rhythms.
Sleep-wake cycle from Dr. Eliza Klearman's website:
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Now let us see how modern ways of living cause disruptions to this optimal cycle. Most of our houses are not built to let much sunlight in. Most people don't get exposed to sunlight in the early morning hours. Also because of being indoors at work or school, there is never enough exposure to sunlight during the day. But there is plenty of exposure to light in the evening hours when our bodies (evolutionarily) can't handle it. Now with the devices we suddenly have bright blue light in our lives in the evening when there used to be moonlight or darkness, just a few decades ago. This delays (may also inhibit) the onset of melatonin production and causes sleep disruption among many other problems.
A little bit of anatomy: Human eye has two kinds of photoreceptor cells -- rods and cones. Rods are responsible for vision at low light levels and cones function when there is bright light.
Human settlements now have well-lit homes, roads, public transport and indoor spaces. I was curious to know what happens to rod cells when there is no dim light at all for many years. I couldn't find any pat answer online. My guess is that the rod cells lose their efficacy since they haven't been used. I have seen the difference in night vision between city folks (used to a lot of artificial lights in the evening) and village folks. In the absence of a bright light in the night, the former can't navigate even in their own apartments; a dim light or darkness just doesn't work for them. Village folks on the other hand are undeterred by darkness outdoors and are confident about their unaided night vision.
All this understanding helped us realize that many conscious choices had to be made to realign ourselves to our evolutionary needs. We now live on a farm where we are outdoor a lot during the morning hours, soaking in a lot of sunlight. In the evening hours we have only warm-yellow LED lights (max 3w) lighting our indoors. The blue component of these lights are insignificant. Dev has a pair of blue light blocking glasses which he uses when needed. We have installed a blue light filter software on our computer. In the night, while sleeping, we have no artificial light indoor or outdoor.
If you are interested in exploring this subject further, here are some pointers:
Dr. Satchin Panda on the importance of darknesshttps://www.darksky.org/
Harvard University's research on blue light and sleep
