Evolution of human colour vision as 'visual purple' receptor proteins, are encoded by Rh1, OPN2 and RHO genes. They are characterized by extreme sensitivity to light and enable monochromatic human vision in low light or dim conditions. They are broken down into retinal and opsin when exposed to these conditions. Humans have 3 types of photopsin proteins found in the cone cells. Long Wavelength Sensitive Opsin (Red cone opsin) – Encoded by the OPN1LW gene with a λmax of 560 that is found in the yellow-green electromagnetic spectrum despite its name. Its sensitivity to the colour red is still known to be higher than the
Evolution of human colour vision ago and 20 45 million years ago. It eventually reached the current λmax of 430 30 million years ago. It is believed that middle and long wave sensitive pigments appeared after the final stages of short wavelength sensitive opsin pigments evolved, and that trichromatic vision was formed through interprotein epistasis. Scientists believe that the slow rate of evolution of human ancestral vision can also be attributed to slow environmental changes. It has been theorized that -shifts might have been required as human ancestors started to switch from leading nocturnal lifestyles to more diurnal lifestyles. This caused their vision to adjust