fenimor writes "The results of the study by researchers at the Biodesign Institute at Arizona State University, suggests that natural genetic selection has provided women with a frequent ability to better discriminate between colors than men. 'Normally, this degree of genetic variation is suppressed through natural selection,' says Brian Verrelli, a researcher at ASU. 'In this case, nature is supporting a high degree of variation instead.' Because women have two X chromosomes, women can receive one chromosome with the typical configuration of the red vision gene while the other chromosome receives a slight variation. By contrast, men have one X chromosome, and any variation in the single red gene that they receive reduces their ability to distinguish between red and green."