Our colorful world — what a joy it is! Who doesn’t love the beauty of butterflies, the colors of birds and tropical fish, or the colorful eyes of a loved one? Mechanistically speaking, though, color is ‘nothing but’ wavelengths of light reflecting off surfaces or emanating from energy sources within a particular range of frequencies we artificially designate as “visible light.” We respond physically to wavelengths only because our bodies come equipped with highly complex sensory systems. We respond emotionally to the qualia of color — the redness of red, the greenness of green, the beautiful spectrum in a rainbow — because of something deeper in our consciousness.
Blind nature is oblivious to qualia. It has no obligation to invent creatures able to manipulate color, or to perceive it. Least of all is nature obliged to produce artists that use color for purely aesthetic reasons unrelated to survival. Yet the living world is filled with colors in profusion, often with spectacular effect. This fact requires an explanation. One could think of reasons natural selection might favor an ecological system of uniform browns or blacks. Camouflage would be perfect in such a world! What does blind evolution care about color?
To outline evolutionary explanations for color, Science Magazine recently presented “The Biology of Color,” a review article by Innes C. Cuthill with 27 authors from the U.K. and U.S. The editors summarize the goal:
Animals live in a colorful world, but we rarely stop to think about how this color is produced and perceived, or how it evolved. Cuthill et al. review how color is used for social signals between individual animals and how it affects interactions with parasites, predators, and the physical environment. New approaches are elucidating aspects of animal coloration, from the requirements for complex cognition and perception mechanisms to the evolutionary dynamics surrounding its development and diversification. [Emphasis added.]
“Elucidating” means shedding light, which presupposes that science does not only observe light, but produces light in the realm of understanding: i.e., scientific explanation. Since we know from the “rules of science” these days that design explanations must be excluded, it’s fair to say this article summarizes the state of the art in evolutionary explanations for color. Contributors include a broad spectrum (so to speak) of scientific disciplines: “evolutionary biologists, behavioral ecologists, psychologists, optical physicists, visual physiologists, geneticists, and anthropologists” — all committed to evolutionary theory. For curious readers, these experts will map the route to proper Darwinian answers, shedding colorful light along the way:
The interdisciplinary field of animal coloration is growing rapidly, spanning questions about the diverse ways that animals use pigments and structures to generate color, the underlying genetics and epigenetics, the perception of color, how color information is integrated with information from other senses, and general principles underlying color’s evolution and function. People working in the field appreciate linkages between these parallel lines of enquiry, but outsiders need the easily navigable roadmap that we provide here.
Following their roadmap, we proceed down the yellow brick road to the wizard of ahh’s, hoping the promised understanding will be forthcoming. For openers, let’s check the flashlight they provide (the “elucidating” device).
In the past 20 years, the field of animal coloration research has been propelled forward by technological advances that include spectrophotometry, digital imaging, computational neuroscience, innovative laboratory and field studies, and large-scale comparative analyses, which are allowing new questions to be asked. For example, we can now pose questions about the evolution of camouflage based on what a prey’s main predator can see, and we can start to appreciate that gene changes underlying color production have occurred in parallel in unrelated species. Knowledge of the production, perception, and evolutionary function of coloration is poised to make contributions to areas as diverse as medicine, security, clothing, and the military, but we need to take stock before moving forward.
This is some high-tech flashlight! We need to learn how to use it, in other words. How do we use evolution to shed light? It is “daunting to the outsider,” they warn. They outline key questions needing elucidation:
- How nanoscale structures are used to manipulate light
- How dynamic changes in coloration occur on different time scales
- The genetics of coloration (including key innovations and the extent of parallel changes in different lineages)
- Alternative perceptions of color by different species (including wavelengths that we cannot see, such as ultraviolet)
- How color, pattern, and motion interact
- How color works together with other modalities, especially odor
Some of us will prefer carrying our trusty ID flashlights for illumination, but let’s give the Darwinians a chance to show off their brand. First, we listen to the commercial:
From an adaptive standpoint, color can serve several functions, and the resulting patterns frequently represent a trade-off among different evolutionary drivers, some of which are nonvisual (e.g., photoprotection). These trade-offs can vary between individuals within the same population, and color can be altered strategically on different time scales to serve different purposes. Lastly, interspecific differences in coloration, sometimes even observable in the fossil record, give insights into trait evolution. The biology of color is a field that typifies modern research: curiosity-led, technology-driven, multilevel, interdisciplinary, and integrative.
Before we rush to buy this amazing flashlight on Amazon, let’s see how well it works. We should be concerned about “evolutionary drivers”, since they are blind, and blindness entails color blindness. How can a blind process understand a trade-off? One thing we learn from the article is that questions about color evolution are producing a flurry of activity among evolutionists:
The study of animal coloration has a venerable history. During the 19th century, early evolutionary biologists set out to explain the diversity of colors that they observed as products of natural selection. The 20th century saw color phenotypes adopted as genetic markers contributing to our understanding of development, genetics, and evolutionary theory.
Before proceeding, we should ask why there is anything else to learn. Didn’t the 19th and 20th century evolutionists figure it out? Apparently not.
In the past two decades, the field has again witnessed explosive growth. Coloration provides exceptional access to phenotypic diversity because we can quantify how color is perceived by the visual systems of diverse species, and humans are visual animals. Contemporary technologies enable biologists to investigate nanoscale and cellular mechanisms producing color; the sensory, neural, and cognitive bases of color perception; and the adaptive implications of external appearances. Progress in each area is rapid, making animal coloration an exciting interdisciplinary field, but one with which it is difficult to keep pace.
Let’s catch our breath in this frenetic race down the yellow brick road, and assess what it is we are looking for. Explanation is not merely description. It’s good to know what gene turns on what color. It’s helpful to find out which colors a predator can perceive. We can even be pleased to learn that a bird of a certain color might have better camouflage. None of these details explain animal coloration. The job of the Darwinians is to tell us how a color-blind process (that doesn’t care whether a creature lives or dies) ended up with a Ladybird beetle’s brilliant reds or a ruby-throated hummingbird’s shimmering throat feathers. It’s not enough to say, “It exists, therefore it evolved.” Nor can they say, “It’s useful, therefore it is adaptive, and natural selection would favor it.” Do you see the circular reasoning inherent in such statements? We seek evidence that evolution did occur, not restatements of what evolutionists believe occurred.
Across animals, coloration serves as a dynamic form of information (Fig. 1). Colorful body parts are moved in behavior, and both pigments and structural colors change at various temporal resolutions. Cephalopods are perhaps the most well-known example, but mobilization of pigments and nanostructures to change coloration is taxonomically widespread. Considerable opportunities exist for dissecting color pigment movements and manipulating their hormonal or neural control. Dynamically changing structural coloration can also manipulate the polarization of light. There is high potential for discoveries regarding how animals perceive polarization and integrate it with color information.
What is “information” to a blind, unguided process? Information fits in well with design theory (e.g., Dembski’s book Being as Communion), but we can’t let scientific materialists employ undefined terms nor import them from a worldview they don’t believe. Information doubles the challenge for evolution, because it requires a transmitter and a recipient that agree on the meaning of the communication.
So far, all we have seen are descriptions, not explanations. Body parts are moved. Animals perceive polarization of light. Animals integrate color information. Great, but how? Why?
We anticipate answers in the subsection, “Genetics of color and evolutionary change.” But careful reading reveals only tricks of the evolutionary trade: co-option, convergence, and similarity. Underneath these superficial narratives, evolutionists need to deal with the origin of complex genetic information, molecular machines, and developmental processes of exquisite order. They try:
For instance, a ketolase enzyme that evolved to modify carotenoid pigments in the retina of birds paved the way for the expression of red pigments in bills and plumage; similarly, the ALX3 transcription factor has come to regulate the expression of melanocyte differentiation in striped rodents.
Saying that something evolved does not mean it did. Can a bird reason, “Oh, now I have this ketolase enzyme. I think I’ll color my beak with it.”? Can a rodent think, “Now that I have ALX3, I can put racing stripes on my back and look really cool.”? Obviously not; the materialist cannot ascribe desires or powers to organisms nor to the molecules involved. We cannot stress enough that evolution is blind and color-blind! It is not personal. It is not a force. It could not care less what happens.
Genes underlying color variation offer insight into the predictability of evolution. Convergent phenotypes commonly arise in parallel; the accurate characterization of color phenotypes has revealed independent changes in similar genetic mechanisms, leading to phenotypic similarity between species.
Predictability is certainly a good quality to have in a theory, but did they predict any of this? No; it is all description after the fact, combined with circular reasoning: “It exists, therefore it evolved.” To have the same accidents occur in independent lineages should amount to falsification of the theory. It certainly does not qualify as an explanation.
Multidisciplinary research into the workings of coloration, from genotype to phenotype, and from development to adult, is certainly valuable. We might compare it to discovering an alien spacecraft and figuring out how it works. Such research cannot explain how it emerged by blind, unguided processes. So while we celebrate the progress in understanding coloration, we don’t see in this paper any explanation for it that does not presuppose the success of evolutionary theory.
Whenever they try to link accidents with functions, they run into problems and have to admit ignorance. For instance, Darwin’s sexual selection theory provides a shiny-object narrative at a superficial level, but not at the genetic level:
Genomic insights will prove valuable in investigations of mechanisms by which colorful traits honestly signal individual quality. It is widely accepted that a sexual ornament can reveal quality, because of the challenges associated with producing or bearing such traits, but we remain largely ignorant of the mechanisms that underlie gene-environment interactions causing condition-dependent signaling. Epigenetic studies at the genome scale may offer insight into this question.
Even worse is accounting for structural color. This kind of coloration, seen in birds and insects, relies on precise placement of geometrical molecules at the nanoscale rather than on pigments. How can evolution even approach such masterpieces of “apparent” design?
Knowledge of genetic mechanisms underlying the creation and transport of pigments, such as melanin and carotenoids, has advanced considerably in the past 15 years, but outstanding questions about structural coloration remain. Understanding the genetic control of size and shape dispersion is important because these properties ultimately control optical structures. An appreciation of the genetics of nanostructural color production could also be important for biotechnological applications — for example, the creation of sensors and reporting mechanisms.
The applications mentioned are matters of intelligent design by humans. How could natural selection invent genes that, by accident, are capable of placing molecules in precise positions at the nanoscale that enable them to refract certain wavelengths of light? Then, how does it position them in second-order artistic patterns like those on butterfly wings? Evolutionists admit they don’t know. They sure have their work cut out for them!
The challenge grows as they try to account for “Receptor processing and cognition” in the next section. It grows even more as they try to integrate colors with patterns and motion. We’ve given enough of a taste of their mode of explanation, we trust, to show that evolution is not an explanation; it is belief masquerading as explanation. Like Tom Bethell discussed in Darwin’s House of Cards, evolutionary explanation is a deduction from a pre-ordained worldview that asserts: It is, therefore it evolved. The public deserves better. The public would receive better were alternatives to neo-Darwinism permitted into the discussion. When you only allow one contender in the race, guess who is going to win?
Photo credit: mandy, via Pixabay.