George ILIEV
Early humans had pink skin covered by black fur, similar to modern chimpanzees. Around 2 million years ago as humans were gradually losing their fur to allow easier sweating and cooling, their skin melanin content started to increase as a protection against ultraviolet radiation. This process was driven by natural selection as dark-skinned homo sapiens had an evolutionary advantage under the tropical sun over pink-skinned furless creatures. However, as humans migrated out of Africa and into northern latitudes, the high melanin content of dark skin became an obstacle for the absorption of UV light and the production of vitamin D in the body. This resulted in less calcium in the bones which made them brittle. Natural selection again stepped in, leading to the loss of pigmentation and the return of pink skin in latitudes higher than 46 degrees north, closing the cycle with the early pink-skinned humans.
A similar cycle can be observed in the evolution and loss of fins in ocean-dwelling animals. The fins of ancient fish were lost and became legs when they moved onto land and became tetrapods. The legs were lost and became fins again when the ancestors of whales and dolphins moved back into the ocean.
Many companies share a similar history of cycles of product/brand proliferation and contraction. Starting with one main product, companies like Unilever, General Motors and Google gradually developed an array of brands. However, as market conditions changed and the managerial complexity increased, brand proliferation peaked and the three companies above started scaling down their brand/product portfolios to focus on fewer core products.
The most famous novel in Chinese literature, "Three Kingdoms", encapsulates this cyclical nature in its opening sentence: "The World under Heaven long divided, must unite; long united, must divide".
Researchers used to believe that humans became paler-skinned around 40,000 years ago as they moved north. However, DNA research on a human skeleton found in Spain shows that until the invention of agriculture in the area (around 8,000 years ago), humans still had dark skin. Humans only developed lighter skin when the agricultural cereal-based diet could not provide them with sufficient Vitamin D (previously found in abundance in the meat and berries diet of hunter-gatherers). So the colour of the skin became much more important as lighter skin captures more sunlight and leads to synthesising more Vitamin D.
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