Evolution of human colour vision opsins was increasing from 400 to 430. During this time, Ancestral Boreotherian had two long wave length opsins created by gene duplication, with one retaining the absolute max value of 560, equal to the ancestral value. This led to the creation of the modern human long wavelength sensitive, or red opsin. The other short wavelength sensitive opsin decreased its absolute max value to 530 and became the middle wavelength sensitive, or green-sensitive opsin. This occurred through mutations involving S180A, Y277F and T285A. The order that these mutations took place in the ancestral Boreotheria is currently not fully known. It is
Evolution of human colour vision hypothesized that T285A was one of the first two mutations because absolute max values would be between 532-538 which is close to the absolute value found in human middle wavelength opsins. Normal human trichromats require a mixture of three primary colours for every day colour vision. Protanopes, deuteranopes and tritanopes are all dichromats, meaning they use a mixture of two primary colours to match any specific colour that they see. Thus, they are missing one of the three wavelength sensitive cones. Trichromats with all three cone pigments intact can generally see minimum wavelength differences between <1 and <3 for wavelengths