Another example of how we are programmed not to think?
Racism works according to the same principles as the rabbit spotting a kite in the sky: his survival depends on an instant reaction, so within the blink of an eye he hides.
We humans do not act differently.
For hundreds of thousands of years, a stranger meant danger.
We roamed the earth in small groups, of 20-50 humanoids or humans, or in small tribes of 100-150 (*).
In such a small universe, where the person you knew at age 2 was the same person you knew at age 30, your society was set in stone. There was nobody you did not know.
Spotting someone you did not know, was a shock. An alien could not have been received less welcoming. For such a creature could mean one thing only: danger!
He or she was living the same harsh and dangerous life as yours, and was after your food, after your well, after your cave, after the women of your tribe.
So the poor, single black person walking through an all white neighborhood, basically triggers the same defense mechanism as a kite to a rabbit: in 2013 we know there is no danger, the rational part of our brain now knows about differences.
But how much of our brain is rational? It is nothing but a drip in the evolutionary ocean of time. Our reptilian brain has been drilled inside out for fight or flight. It does not take the time to stop and wonder, check and double check, read, investigate or listen to arguments.
It tells you one thing and one thing only: danger!
At times when all goes well, the economy is booming, we all have jobs and our basic needs have been fulfilled, racism is only a vague tune in the distance. There IS no danger.
That's only the shallow layer on the surface. At times when things do NOT go well, racism rears its ugly head. For someone has to be blamed. For the unemployment, for the frustration, for the poverty. And then the easiest victim is the person or group who looks different.
It is believed that when the economy goes down 1%, racism increases with 1%.
(Nazi Germany anyone?).
And it's fully based on our, very human and fully understandable, desire to not have to think - and just rely on our primal instincts.
(*) Still today, when counting your complete social circle, you might realise that yours exists of that very same number. The average person on Facebook has 120 friends. We are wired to be able to cope with that maximum.