Do 'Simple' Eyes Reflect Evolution?
by Frank Sherwin, M.A. *
The complexity of the vertebrate eye disturbed Darwin, but he supposed it might have originated millions of years ago through a series of small steps that started with a rudimentary light-sensitive spot. Today, evolutionary theory claims that all eyes found in the animal world somehow evolved independently and can supposedly “be traced from a simple ancestral patch of photoreceptor cells.”1 Those same authors stated, “There appears to have been a single evolutionary origin of light-sensitive cells.”2
Non-Darwinists ask, “Just how simple would this ancestral patch of cells be?” Since we cannot go back in deep evolutionary time to investigate these supposed structures, we must work with what we have today. Light-sensitive cells have a protein photoreceptor called microbial rhodopsin that absorbs photons—units of light. Rhodopsin molecules are embedded in a plasma membrane and would have had to evolve via blind chance, if evolutionists are correct.
Rhodopsin is found in Eukaryota (organisms whose cells have a nucleus), and single-celled Bacteria and Archaea. Rhodopsin molecules have ion channels as well as light-driven proton pumps. Could such sophisticated channels and pumps be the product of random evolutionary forces?
When a photon strikes a light-sensitive receptor cell, it causes immediate chemical changes in the rhodopsin molecules called photobleaching. This instant change results in a depolarizing event termed a receptor potential. This is simultaneously converted into an electrical signal, i.e., a current flow. Each signal has a destination such as a nerve net, or a concentration of ganglia (a small mass of nervous tissue including cell bodies and synapses), via a neural projection where the stimulus is then processed. This “simple” patch of photoreceptor cells is actually extraordinarily complicated!
Where did rhodopsin come from? “The origin of the first opsins is a bit murky,” states a University of California Santa Cruz genomics site.3 It looks like rhodopsin has always been rhodopsin, as predicted by creationists.
Today, the “simplest” eyes, called pigment spot ocelli or eyespots, are generally found in very complex animals such as sea stars (starfish), flatworms, and jellyfish.4
Larvae of marine invertebrates—worms, sponges, jellyfish—have the simplest eyes that exist. They consist of no more than two cells: a photoreceptor cell and a pigment cell. These minimal eyes, called eyespots, resemble the ‘proto-eyes’ suggested by Charles Darwin as the first eyes to appear in animal evolution.5
Is an eyespot automatically simple? An evolutionary zoology textbook states:
Eyespots of astonishingly advanced organization appear even in some unicellular forms. That of the dinoflagellate, Nematodinium, bears a lens, a light-gathering chamber, and a photoreceptive pigment cup—all developed within a single-celled organism.6
Despite evolutionary assumptions that “simple” eyes in certain organisms reflect the eye’s early evolutionary development, creationists maintain that invertebrates such as those listed above do not require the more complex eye anatomy found in other invertebrates (like octopus and squid) and vertebrates. They do not need more intricate eyes in order to do what they were created to do, nor are their eyes necessarily primitive.
Euglena, for example, is a single-celled flagellate with over 800 species that contains chloroplasts for photosynthesis but can also feed by autotrophy (the self-manufacture of food from inorganic substances). An evolutionist described the Euglena’s photoreceptor structure as “highly ordered”:
The paraflagellar body—the photoreceptor—is a highly ordered crystalline lamellar structure. Optical diffraction of the electron micrographs and resulting filtered images of the paraflagellar body suggest that it is formed of rods in a helical arrangement.7
No matter the structure, physiology, or overall function of a visual system—either in a “simple” marine larva or the primitive “proto-eyes” imaginatively suggested by Darwin—the systems are incredibly complex and their design shouts creation.
- Taylor, M. et al. 2018. Campbell Biology: Concepts & Connections, 9th ed. New York: Pearson, 310.
- Opsin evolution: origins of opsins. UCSC Genome Browser Wiki. Posted on genomewiki.ucsc.edu.
- Sherwin, F. 2011. “Relatively Simple.” Acts & Facts. 40 (7): 17
- Uncovering secrets of life in the ocean. European Molecular Biology Laboratory news release. Posted on www.embl.de November 20, 2008.
- Hickman, C. et al. 2011. Integrated Principles of Zoology, 15th ed. New York: McGraw Hill, 749.
- Wolken, J. J. 1977. Euglena: The Photoreceptor System for Phototaxis. Journal of Protozoology. 24 (4): 518.
* Mr. Sherwin is Research Associate, Senior Lecturer, and Science Writer, and earned his M.A. in zoology from University of Northern Colorado.
Cite this article: Frank Sherwin, M.A. 2017. Do 'Simple' Eyes Reflect Evolution?. Acts & Facts. 46 (9).