Evolution and selection of trichromatic vision in primates

Trichromatic colour vision is of considerable importance to primates but is absent in other eutherian mammals. Primate colour vision is traditionally believed to have evolved for finding food in the forest. Recent work has tested the ecological importance of trichromacy to primates, both by measuring the spectral and chemical properties of food eaten in the wild, and by testing the relative foraging abilities of dichromatic and trichromatic primates. Molecular studies have revealed the genetic mechanisms of the evolution of trichromacy, and are providing new insight into visual pigment gene expression and colour vision defects. By drawing together work from these different fields, we can gain a better understanding of how natural selection has shaped the evolution of trichromatic colour vision in primates and also about mechanisms of gene duplication, heterozygote advantage and balancing selection.