A Case Study
At Jacob Sivak’s lab at the University of Waterloo researchers have studied snakes and their vision. Snakes do not have eyelids. Instead they have a clear scale called a spectacle that protects the eyes. Now how a snake just happened to randomly develop a clear scale, so it could see and be selected by natural selection, is unknown.
Did each of the snake’s many scales occasionally develop to be clear due to some strange mutation? And at one point, in the evolution of the snake, did that mutation make the scales over the snake’s eyes clear? How did the snakes survive before that lucky mutation? They would have been blind.
But back to our story. When researcher Kevin van Doorn was examining a snake his instrument detected something strange. van Doorn wasn’t looking for it, but he discovered that blood vessels in the snake’s spectacles might obscure the snake’s vision.
How common it has been in the history of science that researchers have made such accidental discoveries. van Doorn’s discovery is a reminder not of how crucial theories are in guiding researchers to their discoveries, but how capricious the process can be. Breakthroughs often are not so much because of our theories, but in spite of our theories, and this should engender some humility, rather than certainty, about our theories.
But getting back to our story, van Doorn’s next move was to study the blood flow through those blood vessels under different conditions. That was the obvious and natural next move. Sivak and van Doorn didn’t need a theory to tell them what to do. van Doorn found that under normal conditions blood flow through the spectacle was cyclical, with periods of reduced and periods of increased flow, thus allowing improved vision at regular intervals.
But when the snake was exposed to a threatening environment the cycle ceased and the flow was minimal, “thus guaranteeing,” Sivak and van Doorn concluded, “the best possible visual capabilities in times of need.”
It was all reminiscent of Leibniz’ theodicy which recognized that while, yes, evil exists in the world (at least some evil is required, Malebranche had pointed out, otherwise the creation would be no different than the perfect Creator), and in fact a great deal of evil exists, what is optimized is the good-to-evil ratio. There could be less evil, the co-inventor of calculus pointed out, but in that case there would be a great deal less good.
Like a good polynomial, the world could be optimized, and it was. This is the best of all possible worlds. Voltaire sarcastically panned the whole idea with his character Dr. Pangloss, but now science seemed to have the last laugh. Perhaps the snake’s spectacle’s are a necessary evil, but their designs are optimized to minimize the negative impact of the blood vessels obscuring the snake’s vision. As van Doorn concluded, “This research is the perfect example of how a fortuitous discovery can redefine our understanding of the world around us.”
But back to our story, we now ask, How exactly did evolution contribute to the research? For that we need to look at the abstract of the journal paper:
The eyes of snakes are shielded beneath a layer of transparent integument referred to as the ‘reptilian spectacle’. Well adapted to vision by virtue of its optical transparency, it nevertheless retains one characteristic of the integument that would otherwise prove detrimental to vision: its vascularity. Given the potential consequence of spectacle blood vessels on visual clarity, one might expect adaptations to have evolved that mitigate their negative impact. Earlier research demonstrated an adaptation to their spatial layout in only one species to reduce the vessels' density in the region serving the foveal and binocular visual fields. Here, we present a study of spectacle blood flow dynamics and provide evidence of a mechanism to mitigate the spectacle blood vessels' deleterious effect on vision by regulation of blood flow through them. It was found that when snakes are at rest and undisturbed, spectacle vessels undergo cycles of dilation and constriction, such that the majority of the time the vessels are fully constricted, effectively removing them from the visual field. When snakes are presented with a visual threat, spectacle vessels constrict and remain constricted for longer periods than occur during the resting cycles, thus guaranteeing the best possible visual capabilities in times of need. Finally, during the snakes' renewal phase when they are generating a new stratum corneum, the resting cycle is abolished, spectacle vessels remain dilated and blood flow remains strong and continuous. The significance of these findings in terms of the visual capabilities and physiology of snakes is discussed.
As you can see, in the journal paper the research results have been cast into the evolution template. The eyes of snakes are “well adapted” yet there is the presence of the blood vessels. Therefore one would predict that evolution would mitigate such an impact. In other words, it was evolutionary theory that led to the discovery.
But of course evolutionary theory did no such thing. So this is the role of evolution, as an after-the-fact framework to which the results must be conformed in a fictional reconstruction of events.
Like the wicked witch of the west, evolution threatens and demands acquiescence from its soldiers while adding nothing.