For most of our evolutionary history, human activity has been tied to sunlight. Technology has freed us from these ancient sleep-wake cycles, but there's evidence that sunlight has left and continues to go away its mark.
Not only can we get up throughout the day and sleep at night, we are able to thank light for a lot of other points of our biology.
Light can have forced our ancestors to walk upright on two legs. Light helps explain the evolution of our skin color, why a few of us have curly hair, and even the dimensions of our eyes.
As we'll explore in future articles on this series, light helps shape our mood, our immune system, the best way our gut works, and more. Light could make us sick, tell us why we're sick, then cure us.
Millions of years of evolutionary history mean that humans are still very much creatures of sunshine.
We stood up, then moved out of Africa.
The first modern humans evolved in the nice and cozy African climate. and reducing exposure to Strong sunlight is An explanation Because man began walking upright on two legs. When we're standing and the sun is directly overhead, the daylight is way less visible to our body.
Can even have curly hair. Protected us from the recent sun. The idea is that it provides a thicker layer of insulation than straight hair to guard the scalp.
Initially there was additional sun protection in the shape of strongly pigmented skin. Sunlight breaks down folate (vitamin B9), accelerates aging and damages DNA. In our vibrant native climate, dark skin is protected against it. But this dark skin still confessed. Sufficient UV light To stimulate vital vitamin D production.
However, when people settled in temperate regions with weak light, they Frequent light skin preparationthrough different genes in several populations. This happened rapidly, perhaps within the last 40,000 years.
With less UV radiation near the poles, less pigment was needed to guard sunlight from breaking down our folate. Lighter skin also gives more exposure to less light so the body could make vitamin D. But there was one major drawback: less tint meant less protection from sun damage.
This evolutionary background contributes to Australia having certainly one of the best rates of skin cancer on the earth.
Our colonial history implies that over 50% of Australians are of Anglo-Celtic descent, with light skin, transplanted to a high UV environment. No wonder we “Sunburn country“
Sunlight has also played a job in changes within the human eye. Human irises from high latitudes have less protective pigment. They have too. Large eye sockets (And possibly eyeballs), possibly Acknowledge the more precious light..
Again, these characteristics make Australians of European descent particularly vulnerable to our harsh light. So it's no surprise that Australia is outstanding. High rates of eye cancer.
We can't shake our body clock
Our circadian rhythm – the sleep cycle driven by our brains and hormones – is one other piece of heavy evolutionary equipment triggered by light.
Man adapts to the sunshine of day. in vibrant light, Humans can Look carefully And what is healthier? Color vision. But we see poorly in dim light, and we lack senses like sharp hearing or a keen sense of smell to compensate.
Our closest relatives (chimps, gorillas, and orangutans) are lively throughout the day and sleep at night, supporting the concept that early humans had similar day by day behaviors.
This lifestyle probably stretches back to the dawn of primates, before the good apes, in our evolutionary history.
Early mammals were generally nocturnal, hiding from the dinosaurs using their small size and canopy of darkness. However, meteor impacts that worn out these fearsome reptiles allowed some mammals, especially primates, to survive. Mass produced Daily lifestyle.
If we inherited our daylight activity pattern directly from these early primates, this rhythm would have been a part of our lineage's evolutionary history for about 66 million years.
This explains why our 24-hour clock is so hard to shake. It is deeply rooted in our evolutionary history.
One after the opposite. Improvements in lighting technology It has increasingly freed us from dependence on daylight: fires, candles, oil and gas lamps, and eventually electric lighting. So we are able to theoretically work and play at any time.
However, our cognitive and physical performance deteriorates when Our internal daily cycles are disturbed.For example through lack of sleep, shift work or jet lag.
Futurists have already considered circadian rhythms essential for Life on Mars. Fortunately, a day on Mars is about 24.7 hours, the identical as our own. This minor difference needs to be the least of problems for the primary intrepid Martian colonists.
NikoNomad/NASA/Shutterstock
Light remains to be changing us.
Over the past 200 years, artificial light has (partially) helped to uncouple us from our ancestral circadian rhythms. But in recent many years, it has damaged our eyesight.
There are many genes related to myopia. Be more common A surprising example of rapid evolutionary change within the human gene pool, in only 25 years.
And if you have got some genetic predisposition to myopia, less exposure to natural light (and more time spent in artificial light) makes it more likely. These significant changes have occurred within the lives of many individuals.
Light will undoubtedly proceed to shape our biology for hundreds of years to return, but these long-term effects will be difficult to predict.