Chromostereopsis - Evolutionary Significance

Evolutionary Significance

Chromostereopsis may also have evolutionary implications for predators and prey, giving it historical and practical significance. Possible evidence for the evolutionary significance of chromostereopsis is given in the fact that the fovea has developed in the lateral eyes of hunted animals to have a very large angle between the optical axis and visual axis to attain at least some binocular field of view. For these hunted animals, their eyes serve to detect predatory animals, which explains their lateral position in order to give them a full panoramic field of view. In contrast, this observed foveal development is opposite in animals of prey and in primates. Animals of prey and primates depend primarily on binocular vision, and therefore their eyes developed to be frontal in position. The angle between their optical and visual axis, therefore, can be reduced to almost negligible values, down about five degrees in man).

Butterflies may also have taken evolutionary advantage of chromostereopsis in developing distinctive "eye" patterns, which are presented on their wings. These eyespots can appear as being forward or receding in depth based on their color pattern, producing an effect of protruding or receding eyes, respectively. Natural selection may have developed these color and texture schemas because it produces the illusion of protruding or receding eyes of much larger organisms than the actual butterfly, keeping potential predators at bay.

Yet another evolutionary example of chromostereopsis comes from cuttlefish. It has been suggested that cuttlefish estimate the distance of prey via stereopsis. Additional evidence suggests that their choice of camouflage is also sensitive to visual depth based on color-induced depth effects.