Is the eye proof that it didn’t come from an intelligent designer?

The answer is no. The eye is not wired backwards and today I’m going to show you how new scientific research has uncovered powerful evidence of designing intelligence behind the evolution of the vertebrate eye. 

The eye has a special place in the history of discussions of whether our bodies evolved through the guidance of a designer or evolved through random processes. William Paley advanced what has come to be known as the watchmaker argument in which he compared the intricacy detail and sophistication of a watch to the human eye.

“Let’s say you’re walking around and you find a watch on the ground. As you examine it you marvel at the intricately complex interweaving of its parts, a means to an end. Surely you wouldn’t think this marvel would have come out by itself. The watch must have a maker. Just as the watch has such complex means to an end, so does nature to a much greater extent. Just look at the complexity of the human eye. Thus we must conclude that Nature has a watchmaker too.” This is William Paley from his book Natural Theology. 

This argument has in many ways dominated the debate between intelligent design advocates – those that believe evolution must have a guiding intelligence behind it – and Darwinists – those who believe that random mutation and natural selection are sufficient to explain the complexity of the natural world. Since Paley gave the eye as an excellent example of design, it was a seemingly powerful blow when atheist such as Richard Dawkins in his books The Blind Watchmaker and The Greatest Show on Earth argued that actually the eye is an example of bad design. So what does he say? An essential part of the eye is the retina, a layer of cells at the back of the eye. Light enters the eye and hits the retina activating light-sensitive cells known as photoreceptors which then communicate with the brain via the optic nerve. The first criticism Dawkins makes is that the light-sensitive cells known as the photoreceptors that receive and process light before communicating with the brain are situated at the back, the retina. In other words between the light entering the eye and the light hitting the photoreceptors, the light has to pass through layers and layers of other cells that aren’t the photoreceptors. These are the cells Dawkins argues scatter the light resulting in a poorer image in the end.

The second criticism he makes is that the wires that connect the photoreceptors to the brain via the optic nerve run over the surface of the retina instead of just passing out the back of the eye. This he argues produces a design flaw where the optic nerve leaves the eye at this blind spot. There are no light-sensitive cells leaving a portion of each eye with a blind spot which is nevertheless covered by the other eye. Dawkins ends his analysis with the following words “Send it back. It’s not just bad design, it’s the design of a complete idiot.” 

And Dawkins isn’t the only one making this criticism. Evolutionary biologists such as George Williams, Kenneth Miller, Douglas Fatima and Jerry Coyne have all decried the wiring of the vertebrate eye as “stupidly designed”, “a functionally nonsensical arrangement” and an example of how Darwinian evolution “yields fitter types that often have flaws. These flaws violate reasonable principles of intelligent design.” But are they right?

Well no. They’re completely wrong and for two reasons. Firstly, the vertebrate eye could never be wired with the light-sensitive cells at the front of the retina. This is because the light-sensitive cells are among the most metabolically active and demanding cells of the body. This means that they require oxygen and nutrients more than any other cells. As a result they require a blood supply that is closely connected to them. This is provided by a collection of vessels known as the choroid which sit right behind the retina at the back of the eye. The problem is that the blood supply, as well as carrying oxygen and glucose to the eye cells, also carries a host of other chemicals like growth hormones and inflammatory signals. These are important in promoting blood vessel growth but if they were permitted to seep into the layers of the retina they would lead to rapid and catastrophic blindness. Like the roots of trees invading the foundations of a house, blood vessels would invade the retina and uproot and destroy the light-sensitive cells. What prevents it from happening is a barrier known as the brain-eye barrier provided by a layer of tightly packed cells known as the retinal pigment epithelium or RPE. Now the RPE is really important. When the RPE barrier which protects the retina from the growth hormones in the blood vessels is damaged or gets thinned out with age, you can get a catastrophic condition known as wet macular degeneration which can result in total loss of central vision. In addition to this function, the RPE is also as the name suggests heavily pigmented. Unlike the superficial layers of the retina which are transparent to allow light to pass through them, the RPE is dark which makes it ideal for absorbing light. This is essential to prevent the scattering of light in the eye which would result in blurred vision as well as radiation damage to the retina. Now it should be obvious as to why we can’t move the light-sensitive cells or photoreceptors to the front of the retina. If we do so, we also would have to move its blood supply to the front as well as the RPE that provides that brain-eye barrier. If we put the RPE and blood supply in front of the light-sensitive cells then that would block all light getting to the retina because the RPE is pigmented and absorbs light. But we can’t put it behind the light-sensitive cells either. This is because the light-sensitive cells connect with other nerve cells that transform the light energy into electrical energy for transmission to the brain known as bipolar cells. Putting a whole lot of blood vessels and a bearing between them would fundamentally prevent that process. If the nerve wires poked holes in the RPE barrier then that would render it completely useless and make the eye immediately susceptible to the catastrophic blindness we talked about earlier. So it isn’t just a case of moving a bunch of light-sensitive cells to the front of the eye, you also have to move the entire supporting infrastructure too. The funny thing is that this has all been known for decades even before the publication of the blind watchmaker. If Dawkins had, as in the case of our previous video on the recurrent laryngeal nerve, simply done a little bit of research he wouldn’t have made this blunder.

But there’s even more to the story. New research has shown that the design of the eye is even more remarkable than previously thought. With a new design feature that does away with the criticisms of Dawkins and others completely. Using new techniques from astrophysics and astronomy, researchers from Israel’s Institute for Technology had a detailed look at the cell known as the muller glial cell in the retina. Now this cell spans the depth of the retina protruding from the surface and diving down all the way to the back of the retina where they connect with those light-sensitive cells, the photoreceptors we’ve been talking about. These research has found that the more glial cells act as fiber optic cables, concentrating light from the surface of the retina by a factor of 10, and channeling them through the retina to specific light-sensitive cells. In fact these fiber optic cable cells were doing more than even that. Each light-sensitive cell was receiving light from the fiber optic cable cells that was specific to the wavelength it’s specialized in processing. The fiber optic cable cells were acting as funnels concentrating and selecting light specific to the wavelength each individual sensitive cell was specialized for. The research has found that this process improved daytime vision without compromising night vision at all.

So in summary the criticism of Dawkins and other evolutionary biologists was an argument from ignorance. Failure to appreciate the importance of the retinal pigment epithelium barrier as well as the high blood flow requirements of the light-sensitive cells led them to make absurd claims about the poor design of the eye. Failure to show humility in a field that was still under investigation led them to hastily pronounce a judgment on the design of the eye. What they criticized as poor design is actually a fantastic design feature.

As a final note, I’ll say this. This whole episode illustrates brilliantly why a teleological approach to biology – that is assuming the designers behind nature – is much better for science than atheistic approach. An atheist approach takes for granted that mistakes and flaws will be present in nature. This will make scientists lazy when looking for further details and functions. This is exactly the infamous mistake made by geneticists with non-coding DNA wrongly termed junk DNA and it’s exactly the same mistake made by Dawkins and others with the design of the eye.