Does the Diversity of Eyes in Nature Support Evolution?

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Abstract

Evolutionary scientists believe they can map the eye’s evolutionary history by looking at the diversity of eyes in nature, but Bible believers see in this visual diversity the hand of the wise Creator, God.

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Simple or complex, small or large, conventional or unusual, the many sorts of eyes in the biological world are perfectly suited to the creatures they serve. When lined up according to complexity, they form a sequence that—according to evolutionists—affirms the prophetic power of Darwinian thought. “Inside the Eye: Nature’s Most Exquisite Creation,” a recent National Geographic feature, paints the many eyes in nature as masterpieces of evolution, each representing an evolutionary stage.

The National Geographic author accuses creationists of misusing Darwin’s famous quotation in which he supposedly called the idea that eyes could evolve “absurd.” We at Answers in Genesis do not. Refuting this misconception, Dr. Tommy Mitchell in “Didn’t Darwin Call the Evolution of the Eye Absurd?” includes Darwin’s quotation in its entirety. He points out that Darwin’s God-rejecting presupposition that evolution was our “maker” led him to believe that the existence of eyes at such varying complexity was evidence that natural selection really was the agent the built them all, no matter how “absurd” such a notion seemed.

Observations and Evolutionary Conjectures

The National Geographic article is based largely on the work of Lund University’s Dan-Eric Nilsson. The Lund Vision Group explores topics ranging from night vision, deep-sea vision, and color vision to the navigational abilities of birds and beetles. Our appreciation of visual diversity is augmented by the information they and groups like them gather about the structure and function of the many eyes of the world.

Nilsson’s particular interest is in the box jellyfish, and he is an expert on the animal’s 24 eyes and the different jobs they do. This tiny sea creature, as shown in National Geographic, is equipped with four six-eyed clusters (rhopalia). Each cluster is attached to a flexible stalk. Within each cluster (rhopalium) are not only four simple light-detecting eyes but also two low-resolution lensed eyes, one of which is always aimed upward thanks to a bit of ballast in the cluster. The lower-lensed eye equips the box jelly to avoid obstacles, and the up-turned eye—by detecting the variation in light from above—equips the brainless little animal to remain in food-rich regions beneath the mangrove branches where it thrives and survives. Nilsson believes that when the eyes in nature are lined up from simple to complex, they reveal how eye evolution must have happened. Thus the box jelly’s rhopalium is practically an evolutionary model on a stick!

Indeed, the world is full of eyes. The simplest are not really eyes in the usual sense of the word but are simply spots of light-sensitive pigment, which even some microbes have. If a patch of light-sensitive cells is cupped, the shadows cast by its edges provide more visual information than a flat patch, and it is this sort of eye that a flatworm uses to steer itself through life. More information about the outside world is available to animals like the chambered nautilus, which sees dimly through an eye like a pinhole camera. Compound eyes come in a wide variety of forms. And, of course, humans and many animals as different as the octopus and ocelot have a camera eye, yet even the camera eye’s construction varies greatly. Each sort, whatever its apparent limitations, equips its owner for a particular lifestyle. Each is an example of the careful engineering and particular provision of the Creator God.

Conventional wisdom holds that the eye evolved separately—or convergently—at least 40 times.

Eyes—even very complex ones—were present during the Cambrian explosion. Nilsson notes, “It’s amazing how little has happened since then.”1 The fossil record does not document an evolutionary sequence of eye development. Failed by the fossil record in his search for the eye’s evolutionary history, Nilsson asserts that eye evolution can be seen in living creatures. Living animals, presumed to be descended from divergent evolutionary lineages, display so many different sorts of eyes, with so many different components and features ranging from simple to complex, that evolutionists cannot trace a single evolutionary path for eyes. Instead, conventional wisdom holds that the eye evolved separately—or convergently—at least 40 times.

Though for the eye, evolutionists cannot trace a single path through these distinctly different lineages, Nilsson explains that the eyes represented among them are nevertheless examples of evolutionary stages, with each being a fully functional form that meets its owners’ needs. He believes this reveals why some living animals have “primitive” eyes, for evolution needed to go no further with random experiments in eye design in that particular animal.

Evolutionists assert that while each sort of eye developed separately, it acquired all the additional components it needed by modifying existing structures to perform new functions. For instance, in a 2008 You Tube video, Nilsson asserts that the typical lens evolved after water trapped between a couple of transparent membranes focused light onto a light-sensitive retina. Nilsson injects increasing amounts of water between two sheets of clear plastic and explains, “So we can make it gradually from no lens at all and just continue to inject more water, making the lenses bulge more and more and the image becomes gradually sharper and sharper.”2 Treating his model as if it represents observable history, he says, “So we can go all the way gradually, in very small steps, from a simple pigment cup-eye—which has barely got the ability to determine the direction of a light source—all the way to a compete camera-type eye, the same type as we have ourselves, and that is really exactly the way eye evolution must proceed.”3

Using models like this and computer simulations based on the many eyes in nature, Nilsson says he has shown that evolution could build a sophisticated modern eye, starting with a flat patch of light-sensitive cells in just 364,000 years. (He is referring to his own 1994 study, “A Pessimistic Estimate of the Time Required for an Eye to Evolve.”) Because each eye, however primitive, is fully functional and perfectly suited to the lifestyle of the creature that has it, Nilsson believes that eye evolution was never hampered by the problem of irreducible complexity—the idea that a structure whose function depends on multiple components will not be able to confer a significant survival advantage unless all the components appear at once.

That many sorts of eyes are useful to many different sorts of creatures does not, however, demonstrate that the eye evolved through a series of small steps. If a person already holds an evolutionary worldview of the unobservable and scientifically untestable past, then Nilsson’s story of how evolution built the eye might seem like an acceptable model. It’s a great story, and all the evolutionary stepping-stones are there. At least they are there in a computer simulation, but a computer simulation is not the same thing as experimental biology. The ability to simulate something on a computer is no guarantee that it can happen in living organisms, much less that it happened in billions of living organisms over millions of unobservable years. The insurmountable problem is, from a biological standpoint, that there is no experimentally demonstrable way to get from one step to the next.

Root of All the Branches

Nilsson asserts that evolutionists have also found evidence of the common ancestor linking the convergent evolutionary lines of eyes together at their root. That evidence takes two forms: genetic and molecular.

A commonly designed genetic switch does not demonstrate a shared evolutionary lineage but only affirms that a common Designer designed the genetic language used by all living things.

The genetic “evidence” is the Pax6 gene, a genetic switch that, as National Geographic explains, “controls eye development in virtually every creature with eyes.” However, when a mouse’s Pax6 gene is used in the laboratory to switch on eye development in a fruit fly, the fruit fly develops not a mouse eye but a fruit fly eye. Why? Because the switch turns on development for the kind of eye programmed into the DNA God gave the created kind that includes fruit flies.4 As we’ve discussed many times,5 a commonly designed genetic switch does not demonstrate a shared evolutionary lineage but only affirms that a common Designer designed the genetic language used by all living things. Furthermore, it turns out that there is no single gene that regulates eye development across all phyla with eyes, and the control of eye development in an embryo is quite complex. The notion that a single master gene is responsible for eye development across all kinds of animals that have eyes might be taken by those with an evolutionary worldview as support for their belief in common ancestry, but it is an oversimplification.

All eyes, even the most complex, are built on the same basic theme: elaborately tricked-out versions of a simple light detector. Light detection, biologically speaking, begins with a protein—an opsin—that changes shape when it absorbs light.6 This shape change is reversible, whereas a structurally similar molecule—melatonin—is destroyed when it absorbs light. Evolutionists, of course, consider melatonin, a hormone found in many organisms, to be the molecular ancestor of all opsins due to this structural similarity—evidence of molecules-to-majestic-vision evolution. Such magical thinking ignores the chasm of complex problems in explaining how the genetic code to produce such molecules came to exist in the first place, how the arrangement of atoms in a molecule came to represent information, and how the machinery to read and implement that information came into being.

Molecules behave the way they do because of their structure—that’s how God designed biochemistry to work. That eyes across the biological world rely on a family of molecules (opsins) structurally similar to melatonin but with just the right difference to make them function as needed—to reproducibly change shape when touched by light—affirms the existence of a wise intelligent designer, the Creator God attested to in the Bible. Read more about these opsins in “Review: Your Inner Monkey” and “Perfect Molecule Shows Eyes Were Designed.”

Blind Evolution?

Some animals—like blind cavefish—have even lost their ability to see. National Geographic asserts, “They are a testament to both evolution’s endless creativity and its merciless thrift.” However, these Mexican tetras did not evolve into something different. Blind cavefish are just varieties of their sighted surface-dwelling cousins. They are even the same species. They could be seen as an example of how natural selection leads to variety within a created kind, but they are not a testament to evolution. In fact, as we discussed in “How Cavefish Went Blind, and Why It Matters,” natural selection has not even rooted out the genetic raw material coding for eyes from the dark cave population. That genetic material remains unexpressed in the cave population but does not disappear, being preserved by a recently discovered molecular mechanism. This makes rapid adaptation back to a lit environment possible. Evolution has no such foresight. Who but our all-knowing God could have foreseen that an eye-loss option could be useful for certain animals in certain circumstances in this cursed world?

The Human Eye

Evolutionists are fond of looking at the human eye and pronouncing it flawed. They assert that, if God existed, He was a rotten designer. And they claim that the human eye’s flaws demonstrate that it is an imperfect evolutionary product because evolution can only work with material already evolved. It cannot foresee its needs or re-boot for a better result. As National Geographic says, “Our retinas are bizarrely built back to front. The photoreceptors sit behind a tangled web of neurons, which is like sticking a camera’s wires in front of its lens. The bundled nerve fibers also need to pass through a hole in the photoreceptor layer to reach the brain. That’s why we have a blind spot. There’s no benefit to these flaws; they’re just quirks of our evolutionary history.”

Retina Micrograph

Image courtesy of Dr. David Menton.

This layered arrangement is shown in this light micrograph of the retina. Notice the choroid and pigmented epithelium, between the protective sclera and the photoreceptor cells. In this arrangement—despite evolutionary claims to the contrary—lies the true advantage of our eye’s design. Our consistently sharp vision depends on the rapid breakdown of toxic molecules and free radicals generated by interaction with light. This cleanup occurs in the pigment epithelium. And this mopping up operation is metabolically costly. The blood flow to the retina, located in the choroid, far exceeds the nutritional and oxygen needs of the retina. Why? Because God designed our eyes to work efficiently and continuously! He therefore placed the pigmented epithelium and the blood supply to the retina right beside the photoreceptor cells in which all those toxic by-products are generated. It is only the impact of sin’s curse on our bodies that has led to the malfunctions we encounter in this otherwise optimal design.

What about that blind spot? The nerves must exit somewhere. God has designed the human eye’s blind spot—where neurons exit en route to the brain—to be offset from the point at which light is most sharply focused. And since we have two eyes, this “blind spot” is not a problem; our brain compensates and fills in the necessary gaps, using information from the other eye if necessary. Meanwhile, the point of sharpest focus occurs at the one point on the retina where the photoreceptor cells—all cones—have no overlying neuron fibers or blood vessels, allowing 100% of the incoming image to be focused at the spot with completely unimpeded access to a densely-packed region of photoreceptors, those designed to provide the sharpest visual acuity in bright light. As to the rest of the retinal surface, our vision is not fuzzy from having to see through this so-called tangled web that a “bad designer” deposited between them and the light. On the contrary, our Intelligent Designer, the Creator God of the Bible, designed Müller cells, whose funnel-like tops virtually cover the retinal surface, to gather the incoming light and, like fiber optic cables, carry the images in it to the light-sensitive cells.

This is what evolutionists call a “workaround,” as if the random processes of evolution could assemble a structure so irreducibly complex—optimizing light transmission and visual acuity while creating a pigment epithelium rich toxin-neutralizing enzymes and an extremely high rate of blood flow7 to supply it and placing them right beside the cells that need them. The human retina is not bizarre; it is brilliant; it is the work of the Creator God. “The hearing ear and the seeing eye, the Lord has made them both” (Proverbs 20:12).

Be sure to learn more about God’s good design for the human eye in “The Seeing Eye,” “Darwin vs. the Eye,” and “The Human Retina Shows Evidence of Good Design.”

Dr. Tommy Mitchell, a physician and Answers in Genesis speaker, elaborates on many problems with claims that vision evolved and shows how perfectly the human eye is designed in this online video Evolution: The Eyes Don’t Have It.

Seeing the End of the Matter Clearly

The National Geographic article treats every aspect of our world of vision as an evidence for evolution: eye diversity and the fact that eyes share common designs; the fact that some are complex and others are “primitive”; the fact that all components of complex eyes are found in the Cambrian explosion without any evolutionary antecedents and the fact that these same sorts of eyes exist today without any further evolutionary tinkering. The article extols eyes as a family of exquisitely designed evolutionary products because they are perfectly suited to the creatures that have them. Then it points to the human eye’s supposedly flawed (but actually very good!) design as further proof that eyes evolved. Yet all these angles on eyes only support evolution if the viewer—ignorantly or otherwise—already believes that molecules-to-man evolution is possible and rejects the true story of origins provided in God’s Word.

The amazing diversity of eyes makes sense when we accept God’s account of our origins in Genesis.

Each animal’s eye, like the human eye, is designed to meet the needs of its owner. Not because evolution made them that way—for neither the random processes of evolution nor natural selection had any way to do it—but because our wise Creator God did. There is even a microbe with an eye-like structure built of subcellular components! The amazing diversity of eyes makes sense when we accept God’s account of our origins in Genesis. God made many different kinds of fully functional living things in the beginning, and each reproduces after its kind. For 6,000 years, the living things God created have developed many variations, but no kind of living thing has evolved into any other kind. All the necessary complexity needed by each kind of creature was there in the beginning. Therefore, complex structures—like the many different sorts of complex eyes found in nature today and even in the Cambrian explosion—did not have to evolve. God equipped each kind of living thing with the eyes or other light sensitive structures it might need for its lifestyle from the beginning.

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Footnotes

  1. Ed Yong, “Inside the Eye: Nature’s Most Exquisite Creation,” National Geographic, January 14, 2016, http://ngm.nationalgeographic.com/2016/02/evolution-of-eyes-text.
  2. “How the Eye Evolved,” YouTube video, 4:07, posted by “DonExodus2,” June 28, 2008, https://www.youtube.com/watch?v=duBW9QabXfw.
  3. Ibid.
  4. Pax6 also has additional functions, as it (and its homologues) are expressed at many other sites in a developing organism. And eye development is controlled by more than just this particular genetic switch.
  5. See for instance “Cousin Fly,” “Mouse Memory Enhanced By Humanized ‘Language Gene,’” “Developments in Fish Said to Show How Limbs Evolved,” and “Does the Spotted Gar Harbor a Fish-Finger Connection?
  6. Strictly speaking, the opsin’s response to light is indirect. An opsin-type protein—and there are thousands—is paired with a photon-absorbing chromophore molecule. The chromophore’s shape change triggers a shape change in the opsin, and the series of chemical reactions this triggers results in an electrical signal that is interpreted in animals with brains as visual information.
  7. Choroidal blood flow per gram of tissue is the highest in the body.

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