Human Skin Colour

Today my attention went to the dark patches on the walls and doors of our house. Obviously those are places where we regularly touch and the dark patches are the dirt accumulated. 

I wondered why the dirt is dark/black....But let the search for REASONS wait...What is its civilisational consequence?

 The trigger that initiated my further thought process was the ASSOCIATION we all carry in our minds between dirt and darkness...  The AESTHETIC sense that has taken root in our minds that dark is dirty...The converse of the fact that dirt is dark/black.

 We generally tend to conclude that dark-skinned people are less desirable to interact with than fair-skinned people because of this association of dirtiness with darkness, though the reason for skin colour has nothing to  do with dirt. However we conclude that they are UNCLEAN people! 

 See the roots of RACISM which still exists in various degrees mainly in the West and UNTOUCHABILITY which we claim has been banished in India!! It is arguably alive in the minds of every human being! (But we consciously suppress it's expression on ethical grounds.) Not because anyone is mean or race-conscious. (Perhaps even blacks might be, in the core of their personality, admiring whites!!) But because Nature ordained that dirt will be dark/black! If it had been the other way, that is, if dirt were to be white then blacks would've been considered superior!!

The question as to why dirt is dark and not the other way around remains to be answered....Most probably it relates to the Physics of optical dispersion.

It's another pursuit of thought.