Black and White and wait what about brown?
Skin color is one of the biggest source of discrimination and even violence in history. It became a source of business for fairness cream across the world. So called free media of world who reacts on every word you utter or react on the way of your breathing, is practicing meditation on the topic of fairness cream advertisements. The reason is obvious they get advertisements of crore of rupees.
Though that is not the topic of my discussion in this article. There are many articles are written on various features of humans and evolution. Anthropologist have dedicated their lives on various research on the same but I will focus on only one law of physics and it's impact on features of living bodies.
The law is "Kirchhoff's law of thermal radiation" the law implies that "Objects that are good emitters are also good absorbents" and "Objects that are bad emitters are also bad absorbents".
SO WHAT!
Now keep this law in mind and lets see if we can retrieve some relationship between this natural law and a wonderful complex molecule called DNA.
We all know DNA carries genetic markers and those markers keep changing themselves to suite the echo system due to natural survival instinct.
Sorry for giving this news to fair skin people that there skin tone is actually due to a natural law of thermal radiation rather than some special blood running in their veins.
Jokes apart lets consider those two conditions. First is acute winter
The body temperature is 37 Degree Celsius and outside temperature is 0 Degree Celsius. Body emit the radiations and absorb radiations but in this condition due to much higher temperature body will emit more radiations and will receive less radiations from environment, so by the law of radiations if body emits less to preserve heat it can live with less absorption as anyway that is much less than it emits.
Now take example of sweaty summer
We can clearly see that radiations from outside is much higher than body emits. This conditions is very dangerous as the small amount of net inward radiation will increase body temperature to dangerous levels. So the need would be to emit more to release heat and keep body cooler. With some other mechanism like sweating this is managed by metabolism.
Some of them argue that textbook says that in summer you should wear white, than how this hypothesis is correct?
Don't confuse your self, if you are in direct contact of sun than you need cloths which reflect most of the sunlight (which is lighter color) but if you are in shadow and environment is hot than black cloths are advisable as it will dissipate more heat than white cloths.
So the in the nutshell our DNA acclimatized and evolved to suite the condition. Most of fair skin people's DNA coming from cold places and dark skin people's DNA coming from closer to equator which is hot.
Similar argument to animals as well where animals near pole have whiter body like polar bear with black nose (need to be good absorbent of radiation to sense heat) polar wolf etc and animals in hotter places have darker and colorful skins colors. Yes there may be exception to that as well but by careful analysis we can find some reasons for that.
Similarly the eye color is also dictated by whiter and darker environment. In dark environment (Hot places have really dark nights) you need to absorb lots of light to see hence you will see real black eyes. In poles where you have ice everywhere and in general environment is very bright you need less light to absorb so gray/blues and lighter shades are needed. This is even true in animals of hot and cold places.
Where is brown?
With current growth rate of human wealth and life style soon everybody in the world will start living in comfortable environment. Assume that European and Americans are living comfortable life and world will follow similar life in coming century or so. In America most people live in air conditioned environment most of the time. Home, office and transportation are all controlled to around 20 degree Celsius and on top of that humans are trying hard to control further and control the environment of earth, designing more and more comfortable cloths to eliminate extreme weather exposures. The nights are not darker, the day are not so whiter. Where does it lead to us? If human race survives may be for next 1000 years with this comfort, whiter skins will drop it's shade and darker skins will elevate. That leads to brown skin, brown hair and gray eye humans.
Off course to reach this stage humans need to survive and if somebody discover the gadget to change skin color on click of button than we might never be able to observe this change.
Cheers !!!!
