How lightweight helped shape the color of our skin, eyes and curly hair

Welcome to our series “Featherlight and health”. In six articles we look at the sometimes surprising impact of lightweight on our physical and mental health.

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For most of our evolutionary history, human activity has been linked to daylight. Technology has liberated us from these archaic sleep-wake cycles, but there is evidence that sunlight has left and continues to leave its traces.

Not only are we still awake during the day, but we sleep at night, we can thank lightweight for many other aspects of our biology.

Featherlight may have made our ancestors walk upright on two legs. Featherlight helps explain the evolution of our skin color, why some of us have curly hair, and even the size of our eyes.

As we’ll learn in future articles in this series, lightweight helps shape our mood, our immune system, our gut function, and much more. Featherlight can make us infirmed, tell us why we are infirmed, and then heal us.

Millions of years of evolutionary history mean that humans are still largely creatures of lightweight.

We got up and left Africa

The first newfangled humans evolved in the hot African climate. And reducing exposure to bright sunlight Is one explanation why people started walking upright, on two legs. When we get up and the Sun is directly above us, much less sunlight reaches our body.

They can also have curly hair he protected us from the scorching sun. The idea is that it provides a thicker layer of insulation than straight hair to protect the scalp.

Early A wise man it had additional sun protection in the form of highly pigmented skin. Sunlight breaks down folic acid (vitamin B9), accelerates aging and damages DNA. In our lightweight ancestral climates, gloomy skin was protected against this. But this gloomy skin still confessed enough UV light stimulating the necessary production of vitamin D.

However, as humans colonized temperate zones with lower lightweight, this occurred lighter skin has evolved many timesthrough different genes in different populations. This happened quickly, probably within the last 40,000 years.

With reduced UV radiation closer to the poles, less pigmentation was needed to protect sunlight from breaking down folic acid. Lighter skin also let in more slim lightweight, allowing the body to produce vitamin D. But it had one major drawback: less pigmentation meant less protection from the harmful effects of the sun.

This evolutionary background is why Australia has one of the highest rates of skin cancer in the world.

Our colonial history means that over 50% of Australians are of Anglo-Celtic descent, have fair skin and are transplanted to an environment with high levels of UV radiation. No wonder we are described as “a country scorched by the sun“.

Sunlight has also contributed to changes in human eyes. People living in high latitudes have less protective pigment in their irises. They have too larger eye sockets (and probably eyeballs), maybe let in the more precious light.

Again, these characteristics make Australians of European descent particularly susceptible to our harsh lightweight. So it’s no surprise that Australia has this unusual thing high rate of eye cancer.

We cannot move our biological clock

Our circadian rhythm – the wake-sleep cycle driven by our brains and hormones – is another piece of bulky evolutionary baggage triggered by lightweight.

Humans are adapted to daylight. In the dazzling lightweight people can good to see and improved it color vision. However, we see poorly in dim lightweight and lack senses such as acute hearing or keen sense of smell to make up for it.

Our closest relatives (chimpanzees, gorillas, and orangutans) are also lively during the day and sleep at night, supporting the idea that early humans exhibited similar daytime behaviors.

This lifestyle probably goes back further in our evolutionary history, before the appearance of great apes, to the origins of primates.

The earliest mammals were generally nocturnal, using their miniature size and cover of darkness to hide from dinosaurs. However, the meteorite impact that wiped out these fearsome reptiles allowed some surviving mammals, especially primates, to largely evolve daily lifestyle.

If we inherited our daylight activity pattern directly from these early primates, then this rhythm would have been part of the evolutionary history of our lineage for almost 66 million years.

This explains why it is very challenging to move our 24-hour clock; it is so deeply rooted in our evolutionary history.

Next improvements in lighting technology they freed us more and more from our dependence on daylight: fire, candles, kerosene and gas lamps, and finally electric lighting. So theoretically we can work and play at any time.

However, our cognitive and physical performance deteriorates when our internal circadian cycles are disruptedfor example, due to lack of sleep, shift work or jet lag.

Futurists have already considered the required circadian rhythms life on Mars. Fortunately, a day on Mars lasts about 24.7 hours, which is similar to ours. This slight difference should have been the least of the worries of the first intrepid Martian colonists.

The lightweight continues to change us

Over the last 200 years, artificial lighting has helped (partially) disconnect us from the circadian rhythms of our ancestors. However, in recent decades this has come at the expense of our eyesight.

Many genes are associated with myopia (nearsightedness). become more common in just 25 years, a striking example of rapid evolutionary change in the human gene pool.

And if you have a genetic predisposition to myopia, reduced exposure to natural lightweight (and spending more time in artificial lightweight) increases your likelihood of developing myopia. These noticeable changes have occurred over the course of many people’s lives.

Featherlight will undoubtedly continue to shape our biology for millennia to come, but the long-term effects may be challenging to predict.