"only 6% of our cone cells detect blue, and they are mostly located around the edge of our retina. Of the remaining cones, the ratio of red to green cones varies wildly between individuals.
To find out why this is, Tkačik, along with neurobiologist Vijay Balasubramanian of Penn and colleagues, created a database of more than 5000 high-resolution photographs taken at various locations in Botswana, a place near where humans likely evolved and other primates still live. The same scenes were shot at different times of day, with different exposure lengths, apertures, and distances from the camera. Using an algorithm they developed from previous studies of how human cones detect light, the researchers calculated how many photons of different wavelengths the camera had captured and what cone arrangement would pick up the largest number of them."
... and it matched the arrangement of human eyes.