Biology 202

2006 Third Web Paper

On Serendip

An important part of our everyday lives is being able to see the world in color. Color helps us recognize and distinguish between objects of varying hue and saturation, it attracts our attention, and it serves as a "nonlinguistic code that gives us instant information about the world around us" (1). It enables us to tell whether our steak is medium or rare, to detect whether a newborn child is healthy or jaundiced, to find our car in a parking lot and to know when to slow down, stop, or go at a traffic light. What would our world be like if we could not see color? Just ask someone who is color blind. Individuals with colorblindness are at a seemingly huge disadvantage in our society because they are unable to perceive the world like the majority of the population, and thus are often dubbed disabled.

First, it is important to establish what is meant by color and how we are able to see it. Most scientific sources define color as a sensation produced in the brain by light that enters the rod cells, – one of the two types of photoreceptors found in the retina of the eye, - via the absorption/reflection of different wavelengths and frequencies of photons (4). When light is transmitted from an object to the eye, it stimulates the different color cones of the retina, therefore making the perception of various colors in the object possible. However, this definition does not describe for what purpose color vision evolved and why it is so important from an evolutionary perspective. This paper will attempt to briefly explore the evolution of color vision and how it came to be so useful for our everyday lives. In addition, it will explore the advantages and disadvantages of color vision versus those of color blindness in order to assess whether the human race can look forward to significant changes in the form and function of the color cones in the eye in the future.

Researchers at Caltech have recently discovered that they had been wrong all these years about color vision being developed in primates for the purpose of finding the right fruit to eat when it was ripe. Recently these researchers discovered that the color cones in the eyes of primates (which include humans) are, "optimized to be sensitive to subtle changes in skin tone due to varying amounts of oxygenated hemoglobin in the blood" (5). These findings suggest that color vision evolved in old-world primates for the purpose of distinguishing between changes in skin tone caused by blushing and blanching. Today, we do not utilize color vision solely for seeing emotion or distinguishing levels of oxygenated blood in the faces of mates or enemies as old-world primates used to, but rather, we seem to need color to perform simple daily functions. It seems that color vision was adapted by old-world primates for certain functions and over time has been exapted for a set of different functions in human beings. The reason for exaptation is debatable as many theories suggest different things. Within society, where the cultural norm is that colorblind individuals are in the minority, one might argue that we exapted color vision as an improvement to make us better suited to our environment. Some might even posit that it was a selective advantage for the purpose of survival that eventually led to the development of trichromat vision in primates and hence in humans. This would imply that those who lack trichromat vision are selectively disadvantaged and if individuals in society were competing for survival of the fittest those who are colorblind would lose.

Before categorizing the potential losers of this competition, I should take a step back and recognize that a more politically correct term for the color blind individual has been coined: color deficient (2). Individuals who are color deficient experience color blindness to varying degrees, in which they are unable to perceive differences among some or all colors that others can distinguish. There are varieties within the category of red-green colorblindness, in which individuals lack certain cones in the retina that normally enable them to distinguish between the green-yellow-red part of the spectrum (3). There are also varieties of blue-yellow color blindness, which involve the inactivation of the short-wavelength sensitive cone system whose absorption spectrum peaks in the bluish-violet (3). Monochromacy is the complete inability to distinguish any colors, which also occurs in different forms.

While colorblindness as a disability remains controversial, some argue that individuals with color deficiencies have some advantages that enable them to perform certain tasks better than those who can see color. For instance, color blind hunters are claimed to be more successful at selecting prey against a confusing background, and the military have found that color blind soldiers can sometimes see through camouflage that fools everyone else (3). One might expect the military to develop special recruiting units solely for color deficient individuals, so that they can snatch up the rare and underrepresented talent. However, unfortunately, that is not the case. Certain agencies such as the military, the coastguard, and the Federal Aviation Administration (FAA), perform color blind tests in order to screen potential employees (7). Colorblind individuals do not possess "the ability to perceive those colors necessary for the safe performance of airman duties" according to the FAA (8). Might this suggest that there are safe performance airman tasks that for which color vision was exapted from the old-world primates?

Our society has constructed an environment in which many things we use on a daily basis, such as road maps and traffic lights are color coded, which certainly does not benefit the small portion of the population that can't use them. One might argue that the process of natural selection will eventually weed out those less capable of functioning in our changing environment, but that just doesn't seem fair. Where does that leave the lonely anomalous trichromat, dichromat or monochromat individual (7)? Perhaps over time, within the next few million years, color vision will go through an additional metamorphosis and alter the way human beings live. For instance, perhaps colorblindness will be become more prevalent among individuals in populations over time and the benefits of this condition will outweigh the deficiencies. But until then, it is important to realize that colorblindness is a disability from the perspective of individuals living in a world constructed by members of the majority who perceive their shared surroundings in a different way. Until changes are made to make everyday tasks such as reading a color coded map more accessible to colorblind individuals, they will remain at a disadvantage because they will not be able to function fully in society with the rest of its members. Perhaps one day, it will be those of us who are capable of seeing color dubbed disabled, as the ones who are selectively disadvantaged to function amongst the rest of the population!

Sources:

1) http://psy.ucsd.edu/~dmacleod/221/color%20papers/Neitzreview.pdf - Article entitled Molecular Genetics of Color Vision and Color Vision Defects, by Maureen Neitz, PhD and Jay Neitz, PhD.

2) http://webexhibits.org/causesofcolor/2.html - Website that gives detailed information on colorblindness.

3) http://en.wikipedia.org/wiki/Colorblindness - Free online encyclopedia that provides basic definitions of terms such as colorblindness.

4) http://www.cis.rit.edu/mcsl/faq/faq1.shtml - This site provides answers to color and color perception questions, as well as a nice diagram of the eye.

5) http://www.sciencedaily.com/releases/2006/03/060320221839.htm - Website that publishes daily science news. This particle piece is an article from Caltech on the evolution of color vision old-world primates.

6) http://www.sciencedaily.com/releases/1999/11/991109072142.htm - Website that publishes daily science news. This particle piece is an article from University of Chicago Medical Center on the origin of primate color vision.

7) http://www.agape1.com/color%20vision.htm – Website of the Agape Optometry Center that discusses colorblindness.

8) http://www.leftseat.com/baggish.htm - Website by Pilot Medical Solutions, Inc. that provides an article with details on color vision information for pilots.


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