Abstract
There are three types of account of whether and how primate photoreceptor spectral sensitivities and color vision might have evolved: I) the existing arrangement is sub-optimal, and in particular the spectral separation of the L and M cones reflects their recent evolutionary divergence; II) the spectral sensitivities are optimized for color vision, and III) there is a trade-off between the requirements of chromatic and spatial sampling. The discussion is enlivened by consideration of the diversity amongst New-World primates, where gene frequencies give insight to selection amongst different phenotypes (i.e. varieties of color vision). Different authors find evidence for all the main proposals summarized above, and I will review two particular approaches. First, a model developed by M. Vorobyev, which shows that the human retina is optimal for coding reflectance spectra of colorful objects, such as fruit and flowers. I will then turn to evidence from New World monkeys. This suggests that the 535nm (M) type of pigment gives relatively poor (dichromatic) vision, but that dichromats may be better than trichromats at finding camouflaged insects. The present knowledge does not give a clear account of the selective forces that influence evolution of primate cone pigments and color vision. We have however learnt that, at least for spectral sampling, understanding the evolution and design of the eye requires consideration not only of the natural signals that it encodes, but also how this information is used in making behavioral decisions.