One upon a time there lived two snake brothers in a jungle. One of them was white in colour and other was black. Their parents named them Blacky and Whitey. One day they were playing who will pick the apple from a tree. The apple was a little high and they were finding it hard to reach. In a fit to win, both of them took a big run-up for jumping and struck the apple at the same time. The apple fell, but both of them started fighting over who win. Blacky said he won and Whitey said he won. The fight over apple made them bitter enemies.
One day a white snake was quarrelling with a black snake. Whitey gave the black snake a good thrashing and told the white snake to stay away from black snakes as they are really evil. When Blacky came to know about this, he thrashed a white snake as well and repeated the same message of evil about the white snakes. That day the jungle got divided between black and white snakes. It was impossible for snakes to move about freely in the jungle. Whenever some group of black snakes saw some alone white snake, they would immediately surround and beat him. White snakes did the same to black snakes.
Once a snake catcher came to the jungle. He observed how the black and white snakes behaved. He immediately came up with a strategy to catch snakes. First he used his tricks to catch a white snake. Then he took a big cage and put the white snake in it. He kept this cage in the area that belonged to black snakes. When the black snakes saw a white snake, they all flocked into the cage to attack the white snake. While they were busy beating the white snake, the snake catcher closed the cage and took home a big bundle of black snakes. He sold the snakes in the market to people who liked to eat snakes. He sold all the snakes except one black snake. Next time he put the black snake in the cage and took it to white snakes area. As expected, the white snakes came to attack the black snakes and ended up getting caught in the cage.
This continued for many generations of snakes and snake catchers. Slowly the number of snakes captured by snakes catcher started to decrease. He wasn’t really sure why so many snakes are not attacking. After some time he decided to stop catching snakes as it was not worth the effort. When the snake catcher told this story to his son, he was very much intrigued. He was a biologist and interested in animal behaviour. He took the cage to the forest and caught few snakes and started to compare the snakes who attacked and those who didn’t. It took him long series of experiments to find that the snakes who were not attacking were colour blind. These snakes always saw things in the shades of grey, never quite sure which one is black and which one is white. Some of these snakes were white and some were black. Since these snakes couldn’t distinguish between white and black, they survived. The jungle was grey again with black and white snakes everywhere.