In the UK after quarter-century searching for woman having extra type of cones (cone cells of eye, responsible for color vision) was finally found! Such women may potentially see an incredible number of colors – 99 million. Why only women have this ability and what is the likelihood that your mother or daughter is among such women?
Most of the inhabitants of the Earth have three different kinds of cones with different photopsins. In other words, most people in the world are trichromats and may distinguish about 1 million of colors.
At the same time, men suffering from color blindness, have only two functioning types of cones and one – mutated. They are dichromats and can only see around 10,000 shades. By the way, almost all the mammals, including dogs and New World monkeys, are dichromats too.
As early as in 1948 Dutch scientist Henry Lucien de Vries, who discovered this anomaly among color blind men, found out that their mothers have three types of normal cones and one – mutated. Thus, the assumption was made that tetrachromats exist.
Despite the significance of this finding, no one paid much attention to tetrachromats until the late ’80s, when John Mollon from Cambridge University started searching for women, who might have four functioning cone cells.
Assuming that color blind men pass this fourth cone cell onto their daughters, Mollon estimated that around 12 percent of the female population should be tetrachromats. But all of his tests showed that these women could only perceive the same colors as the rest of us. And that meant that only three of their cone cell types were working, so they were not true tetrachromats.
Then, in 2007, neuroscientist Gabriele Jordan from Newcastle University in the UK, who had formerly worked alongside Mollon, decided to try a slightly different test to look for this super-vision. She took 25 women who had a fourth type of cone cell, and put them in a dark room. Three colored circles of light flashed before these women’s eyes.
To a trichromat, they all looked the same, but tetrachromat had to see difference between circles. To the great joy of scientists, one woman was able to differentiate the three different colored circles in every single test!
Sure thing, the question that has to be answered is if so many female children of color blind men have four types of cones, why scientists were only been able to find one true tetrachromat?
First, research was conducted in the UK only, which significantly narrowed the search.
Secondly, scientists suggest that our “trichromatic” world does not generate anything of such colors that tetrachromates can potentially see. In other words, tetrachromats would never need to use their fourth cone cell type, and so would never realize they had special vision.
But it is highly unlikely that scientists will sink into despair and stop their researches. In particular, they are going to develop special shades to “unleash” the power of tetrachromates.