Why curly-haired people exist: Scientists have explained the origins of these physical traits.

The sunlight not only aids in the production of vitamin D or gives the skin a tan. It has also led to changes in the facial features of our ancestors. Specifically, the effects of sunlight are evident not only in skin color but also in eye size and even curly hair.

As reported by Livescience, dark skin is part of the mechanism that protected against the breakdown of vitamin B9 and skin aging. Curly hair, according to scientists, evolved to shield people from intense sunlight. Curls provide more insulation than straight hair.

When humans migrated from areas with strong sunlight to temperate regions, their skin became lighter. This process took about 40,000 years. However, lighter skin allows for greater vitamin D absorption, albeit with less protection against UV radiation.

Sunlight also contributed to changes in human eyes. People from higher latitudes have less protective pigment in their irises. They also possess larger eye sockets (and likely larger eyeballs), possibly to allow more light in.

Light continues to change us, scientists assert – due to the increase in artificial lighting, human vision is genetically deteriorating. This evolution is occurring at a much faster pace. Many genes associated with myopia (nearsightedness) have become more prevalent in just the last 25 years.

Previously, "Telegraph" reported how much all the people on Earth weigh. Interestingly, human-made objects weigh thousands of times more, while humans constitute only a tiny fraction of the living nature's weight.