An Eye for an Eye: A Layman’s Journey Into The Evolution of the Eye
As of late, I have watched a couple of weak debates between christians and atheists. For a good chuckle and to better understand where I am coming from, take a moment and indulge yourself by watching the following video: Ray Comfort on the Banana.
I’m going to leave the banana part of the video alone. I mean, come on, the banana has been selectively cultivated into what we see in our grocery stores today. God did not intelligently design the banana, man did. Or, perhaps, Chiquita did? Anyway, back on track….
I am going to focus on the overused point of argument featured by some of these weak christian “debaters”: the human eye is too complex to have evolved. In the Ray Comfort on the Banana video, Kirk Cameron (I can’t believe I had a crush on him in the 1980’s) spouts off some memorized biological facts to support the argument that only a creator god could have formed the human eye. Cameron’s proof of the existance of god and intelligent design. He even went so far as to pull the following quote from Charles Darwin out of context to support his argument: “To suppose that the eye, with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree.” (Darwin, On The Origin of Species)
Ahhh…. what we have here is a prime example of quote mining. By taking this quote out of context, it now appears that Charles Darwin believed the evolution of the eye through the process of natural selection is ridiculous or, as Darwin states, “absurd in the highest possible degree.” However, this is not what he ment to say at all. Before I continue, let’s take a moment and visit Darwin’s quote in context:
“To suppose that the eye with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest degree. When it was first said that the sun stood still and the world turned round, the common sense of mankind declared the doctrine false; but the old saying ofVox populi, vox Dei, [the voice of the people is the voice of god] as every philosopher knows, cannot be trusted in science. Reason tells me, that if numerous gradations from a simple and imperfect eye to one complex and perfect can be shown to exist, each grade being useful to its possessor, as is certainly the case; if further, the eye ever varies and the variations be inherited, as is likewise certainly the case; and if such variations should be useful to any animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, should not be considered as subversive of the theory. How a nerve comes to be sensitive to light, hardly concerns us more than how life itself originated; but I may remark that, as some of the lowest organisms, in which nerves cannot be detected, are capable of perceiving light, it does not seem impossible that certain sensitive elements in their sarcode should become aggregated and developed into nerves, endowed with this special sensibility.” (Darwin, On The Origin of Species)
Now, having read this quote in context, Darwin by no means stated the eye is too complex to have evolved over the time. Instead, he stated quite the opposite.
In his book, The God Delusion, evolutionary biologist Richard Dawkins addressed the above quote. Dawkins stated: “Darwin’s fulsomely free confession turned out to be a rhetorical device. He was drawing his opponents towards him so that his punch, when it came, struck the harder. The punch, of course, was Darwin’s effortless explanation of exactly how the eye evolved by gradual degrees.”
Ok, so exactly how can something evolve by gradual degrees? You see, evolution through natural selection is the process by which advantageous changes in phenotypes, or observable traits, are gradually passed down from generation to generation. For example, in Toru El’s article The Two Theories of Evolution, he gives an example of green shelled beetles. These particular beetles move into an area that is predominately brown, and are now more visible to predators. Through a genetic mutation, a beetle is born with a brown colored shell. Because this brown shelled beetle can better blend in with its brown surroundings, it has a higher chance of passing on this mutation to its offspring. Within a matter of generations, a population of brown shelled beetles will form.
In an interview published by The Committee for Skeptical Inquiry, Jerry Coyne, evolutionary biologist from the University of Chicago, discussed two different points of what he considers evidence for the evolution of the eye. For his first piece of evidence, Coyne began by stating “Darwin was the first one to deal with the eye in The Origin of Species, showing we have all degrees of eye development in living species and there is no problem envisioning how you go from one to another.”
The second piece of evidence referenced by Coyne was a paper written by Dan-E. Nilsson and Susanne Pelger, both of Lund University in Sweden, entitled A Pessimistic Estimate of the Time Required for an Eye to Evolve. Nilsson and Pelger were able to map the evolution of their model eye from light-sensitative cells to the camera eye within a time span of 364,000 years. Which, in evolutionary terms, is rather quick. Jerry Coyne summed up the findings of this paper quite nicely: “They made very conservative assumptions about what mutation rates might be, about what the selection pressures are, and in a few thousand generations they saw this eye spot evolve into a complex eye.”
Nilsson and Pelger’s paper was easy to find online. But,I have to admit, this paper was, at times, an intellectual challenge for this layman. However, there is a wonderful YouTube video featuring Richard Dawkins entitled:The Evolution of the Eye (2010). What I loved about this video, is that Dawkin’s explanations not only helped me better understand Nilsson and Pelger’s paper, but also showed examples of modern day organisms that illustrate the different stages in eye evolution.
After all this research, I do have to ask, what’s so great about the eye anyway? If god intelligently designed the eye, then why do the majority of us have to wear corrective lenses, glasses, or undergo eye surgery? My eyesight is so profoundly bad, that, without my glasses/contacts, all I can see are fuzzy/blurry colored blobs. In more primitive times, my poor eyesight would have probably been the literal death of me. While those, like my husband, who have excellent vision would have probably lived long enough to pass their traits of 20/20 vision on to their offspring. Ok, here’s a thought experiment. Would the human eye continue to evolve from its current flawed state if only those who have 20/20 vision were allowed to procreate? Yes, scary thought and one that enters into the ethics of eugenics… but still an interesting thought. Perhaps a topic to research for another time.
I will never look at a banana the same way again (sorry, I couldn’t resist). In all seriousness, the complex eye is the result of evolution, not intelligent design. However, if you feel the need for more research, then by all means do the research!! Hell, don’t go by my research and video suggestions alone, I’m just a layman sharing my own quest for my own answers. One of the beautiful things about living in the 21st century is the fact that you have endless resources at your fingertips! Just a word of warning/advice, be careful when you research. Stick to research done by authorities in whatever field you are researching. Check their sources/references/bibliography and make sure they use a variety of reliable resources. As always, if something doesn’t seem right to you, read, research, ask questions, and think critically for yourself!!
To bookend my blog post, I will leave you with one final quote by Richard Dawkins:
“Creationist ‘logic’ is always the same. Some natural phenomenon is too statistically improbable, too complex, too beautiful, too awe-inspiring to have come into existence by chance…. Therefore a designer must have done it. And science’s answer to this faulty logic is also always the same. Design is not the only alternative to chance. Natural selection is a better alternative. Indeed, design is not a real alternative at all because it raises an even bigger problem than it solves: who designed the designer? Chance and design both fail as solutions to the problem of statistical improbability, because one of them is the problem, and the other one regresses to it. Natural selection is a real solution. It is not only a workable solution, it is a solution of stunning elegance and power.” (Dawkins, The God Delusion)
- YouTube Video: Ray Comfort on the Banana
- On The Origin of Species, by Charles Darwin
- What is Quote Mining?, by Toro El
- Translation of Vox populi, vox Dei; Merrium-Webster
- The God Delusion, by Richard Dawkins
- The Two Theories of Evolution, by Toro El
- To Better Understand Evolution: An Interview with Jerry Coyne, by Felipe Nogueira – Skeptical Briefs Volume 24.3, Fall 2014
- A Pessimistic Estimate of the Time Required for an Eye to Evolve, by Dan-E. Nilsson and Susanne Pelger
- YouTube Video: The Evolution of the Eye (2010)