The Evolution of Color

                                                The Evolution of Color



According to projectivist views about color, color properties do not precede color vision. It is in virtue of color experiences in perceivers that things come to be colored. Color is mind-dependent. I will assume this view here. My concern is with the consequences of this view for the theory of evolution.

            Sensations evolve: they result from genetic mutations acted upon by natural selection. They are adaptive traits, just like bodily organs; they are there for a reason. Thus the feeling of pain has biological utility (as a warning sign and motivator), and even the phenomenological details of the sensation will have been subject to fine-tuned natural selection. The feeling of orgasm must be similar: it is the way it is for strictly biological reasons–as the best method the genes have for securing their survival. These traits are internal—sensations occur “inside” animals. They are part of what we might call the restricted phenotype: they belong with eyes and stomachs and other organs of the body. Their design follows the general rules of trait selection: they are solutions to evolutionary problems, more or less efficient, constrained by the past, and handed down through the generations.

            Tastes and smells are similar, only now it is external objects that have tastes and smells—whereas it is organisms that have sensations. Things taste and smell as they do for strictly biological reasons. As organisms evolve, tastes and smells come into being, though they are tastes and smells of external things. They are projected not inherent, relational not intrinsic. And it is the same for colors: objects are colored but they are so only in virtue of the existence of evolved organisms that see them that way. There were no tastes, smells, and colors before sentient organisms evolved. Thus we can say that colors evolve—like sensations of color. Red objects, say, came into existence (qua red) by means of genetic mutation and natural selection. If red were not an adaptive color for organisms to see, then it would not have evolved: red is a biologically useful color to project. In general, the colors organisms see must have been specifically selected for their adaptive value—presumably because of their ability to provide sharp contrasts (among other things). In other words, natural selection operates on colors—even though it is external objects that are colored (in virtue of color vision). If the genes for color vision were to mutate so as to produce a completely different set of perceived colors, and these new colors were more adaptive than the ones we now see, then we would find a selective pressure in favor of these mutated genes. The world contains the colors it does because of the selective pressures operating on organisms.

            That may sound odd, because colors, unlike sensations, are not properties of organisms—they are properties of external objects (though projected there). They are not part of the organism’s restricted phenotype, i.e. existing within its individual boundaries. But here we must remember the notion of the extended phenotype: it is not just the individual body type that is selected, but also what that body produces environmentally. Thus the beaver’s dam and the bird’s nest are part of these animals’ extended phenotype: natural selection works on the combination of body and external product, so that good dams and nests are favored, along with good limbs and brains. Body plans and behavioral capacities evolve, but so do the adaptive products of those things—she who builds the better dam or nest is most likely to pass on her genes. The unit of natural selection is the extended phenotype not merely the restricted phenotype. And now the point I want to make is that colors are part of an organism’s extended phenotype. They are products of minds and brains, like dams and nests, but they exist outside the boundaries of the organism—hence they belong to the extended phenotype. They evolve by the same rules as bodies, but they are not parts of bodies. As dams and nests evolve, so colors evolve (and sounds, tastes, and smells). Colors are created by genes, ultimately, and the better the color the more chance it has of surviving. The colors we see now in the world have stood the test of evolutionary time. The colors we project are the colors that have passed selective muster. Red, for example, has proved itself a highly adaptive color, along with the usual color spectrum that we see. Wishy-washy or indistinct colors might not do as well in the fight to survive—just as feeble or painful orgasms would not be apt to survive, in contrast to more pleasurable ones. In the case of colors, we might say that they belong to the projected phenotype—which is a subclass of the extended phenotype. The organism builds its physical environment (sometimes), but it also constructs its perceptual environment. It constructs a phenomenal world. This world consists of colored objects (among other things); so colored objects evolve (though not the matter they are made from). Evolution thus operates selectively on phenomenal worlds, as it operates selectively on limbs and brains. Whole species of phenomenal world come into existence by mutation and natural selection.

            Some properties of objects do not evolve—those that precede and are independent of organisms—but some do. Projected properties do, because they reflect the perceptual receptivity of organisms. When I say that colored objects evolve I obviously don’t mean that the objects themselves have evolved by natural selection; I mean that their having the colors they have is a result of natural selection–there are no colored objects on the planet without natural selection. It is because colors are both properties of objects and projected by the mind that they belong to the extended phenotype of the organism. If they were psychological properties of organisms, they would be part of the restricted phenotype; and if they were inherent properties of external things, not projected properties, they would simply be part of the non-evolving environment. The point is not that experiences of color evolve—that follows simply from the fact that sensations evolve. It is rather that the colors that are the objects of such experience evolve—as dams and nests evolve. Dams and nests are adaptive traits for beavers and birds, and colors are adaptive traits for visual organisms—though these traits all belong in the extended phenotype. As adaptive traits, they are subject to evolution by natural selection. The colors that exist in our world are those that have survived the rigors of natural selection.

            It may help in understanding the point if I make the ontology of colors clear. The projectivist view of color is naturally associated with a dispositional theory of color ascriptions: objects have the colors they are disposed to produce experiences of—an object is red, say, in virtue of being disposed to produce experiences of red. This need not imply that colors are identical to such dispositions: we can hold that colors supervene on these types of dispositions, without being identical to them. Then we can say that colors are simple qualities of objects, not in themselves mental, but that they are instantiated in objects in virtue of dispositions to produce color experiences. Color experiences clearly evolve, and objects only have dispositions to produce such experiences in virtue of the existence of evolved organisms; but it is a further claim that colors themselves evolve—conceived as simply qualities of external things. We thus have the nontrivial thesis that objects come to have simple color properties in virtue of evolution by natural selection. A mutation caused some object to look red, and hence (by projection) to be red; then natural selection favored that way of seeing, and hence what is seen. Colors came into the world by the same mechanism as hearts and kidneys. To put it paradoxically: it is adaptive for us to be surrounded by colored objects.

            Does this view of color generalize? It certainly generalizes to other secondary qualities, but it may also generalize to qualities traditionally regarded as primary qualities, such as shape and motion. For it may well be that such qualities do not rightly belong in the austerely objective world described by physics; rather, they reflect our evolved sensibility—how we have been programmed to experience the world. If so, shape and motion—the perceptible qualities we experience—are also evolved (and evolving) entities. Objects have shape and motion, as we perceive them (if not in the austere world of physics), but they do so only as a result of our evolved sensibility; so they too are subject to evolution by natural selection. The whole world of colored objects with shapes and in motion is caught up in the evolutionary process: it originated in that way and its survival depends on the usual evolutionary pressures. In other words, the world we experience is an evolutionary product—like limbs and brains, dams and nests. The empirical world is really part of our extended phenotype.  [1] So the extended phenotype extends quite far into reality (though not all the way). When did this naturally evolved empirical world come to exist? It probably had its early origins in the projective mind of a sentient fish a billion or so years ago. Then it was that the world began to be clothed in color (and maybe shape and motion, as we conceive them in common sense). It has been evolving ever since, becoming ever more complex and subtle. It will cease to exist when there are no more sentient organisms projecting properties onto the world. Colors will eventually become extinct, joining the dinosaurs.


  [1] But not the whole of reality since there is an objective world out there that owes nothing to our evolved modes of experience. It is the world as it appears to us that belongs to the projected extended phenotype—but this world contains real (though projected) properties of things.

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