Chimpanzees can distinguish among colours that other mammals cannot see.Trichromacy, one important property of human vision, is that for most human beings any colour can be reproduced by mixing together just three fixed wavelengths of light at certain intensities. This arises because the retina uses only three types of light-absorbing pigments for colour vision. However, this is only common among primates; almost all nonprimate mammals are dichromats, a few nocturnal mammals have only one pigment, while some others have four pigments and are therefore able to detect ultraviolet light invisible to humans.
Each of the three different pigments absorbs light at different wavelengths- short-wavelength(S) pigment absorbs light maximally at wavelengths of approximately 430 nanometres, medium-wavelength(M) pigment around 530 nanometres and long-wavelength(L) pigment at 560 nanometres. In 1980s, Jeremy Nathans identified the genes for the human pigments. The gene sequences revealed that the M and L pigments are almost identical; the difference in spectral sensitivity between them derives from substitutions in just three of the 364 amino acids from which each is built. M- and L-pigment genes are next to each other on the X chromosome and this explains why a common anomaly in human colour perception, red-green blindness, occurs more often in men than in women. The S-pigment gene is located on chromosome 7, and its sequence shows that the encoded S pigment is related only distantly to the M and L pigments.
In the case of primate colour vision, trichromacy based on the “new” M and L pigments along with the S pigment presumably conferred a selective advantage over dichromats in some environments, such as the ability to tell the colours of ripe fruit(dichromats are less able to distinguish the colour difference in the red, yellow and green regions of the visual spectrum). An improved ability to identify edible fruit would likely aid the survival of individuals harboring the mutations that confer trichromacy and lead to the spread of those mutant genes in the population.
Reference:
Jacobs, G., & Nathans, J. (April 2009). The Evolution of Primate Color Vision. Scientific American , 40-47
