Are Starfish Eyes Missing Links?
Starfish are found to have “primitive” image-forming eyes on the tips of their arms. Do these represent links between simple and complex eyes? Some reporters seem to think so.
Deborah MacKenzie at New Scientist leapt at the opportunity to score one for Darwin:
We have known about the sensors that starfish have at the ends of their arms for 200 years, but no one knew whether they are real eyes that form images or simply structures that detect changes in light intensity.
We finally have an answer: they appear to act as real eyes. The discovery is another blow to creationist arguments that something as complex as a human eye could never evolve from simpler structures.
In a similar vein, PhysOrg asked if it is a “missing link in eye evolution.” Dr. Andrews Garm at the University of Copenhagen experimented on blue sea stars. When deprived of the photosensors, starfish wandered aimlessly, but their fellow stars with intact sensors migrated toward the coral, where the food source is. The article contains photos of the starfish and its photoreceptors.
Surprisingly, after 200 years of knowing these photoreceptors exist, nobody had checked to see if they are capable of providing directional cues to the animals. New Scientist said they are “good enough to show the way home” but more primitive than the compound eyes in arthropods. MacKenzie continued the evolutionary angle:
In evolutionary terms, says Garm, it is interesting because starfish eyes are structurally close in form to the hypothesised first image-forming eyes.
For instance, light receptors in more advanced eyes are built either out of modified cytoplasmic projections called microvilli, or out of filament-shaped cell organelles called cilia. Starfish eyes contain both structures, so “have features that look a bit ancestral“, says [Dan-Eric] Nilsson [Lund University].
“This shows what visual task drove this important step in eye evolution,” says Garm. “Navigation towards large stationary objects – here the reef – that were preferred habitats.” In other words, he thinks our eyes may have first evolved so we could find our way home.
PhysOrg said that the structure on the blue sea star, “except for the lack of true optics, resembles arthropod compound eye.” Neither article mentioned the whole-body lenses on brittle stars, another echinoderm (8/23/01).
In other echinoderm news, PhysOrg reported that some starfish are able to shed arms to prevent overheating. Nature News reported a Cambrian fossil that they claim is an early echinoderm. It lacked arms, but had five-fold symmetry. It “resembled an egg with its tapered end planted in the sea floor,” the article said. “Its mouth opened upward and its body spiralled down.”
Nice try, Darwin Party, but no score. Starfish are not ancestral to arthropods or vertebrates. Eyes appeared abruptly in separate phyla during the Cambrian explosion, as seen in molluscs, jellyfish, comb jellies, and arthropods (trilobites and the Burgess Shale animals), and in some extinct phyla. Trilobite eyes were very complex but appeared abruptly like all the others. If starfish represented a transitional form, why do starfish still exist hundreds of millions of years later with the same “primitive” eyes? Where’s the evolution?
The authors made another tactical blunder in their evolutionary tale. “Visual tasks” do not “drive evolution.” You can’t drive an aimless mechanism on a random walk. Eyes don’t evolve “so we could find our way home.” That makes no sense theoretically or evidentially. All living things have some common “tasks” including finding their habitat. Why don’t plants have eyes? Why don’t seeds have eyes so they can find the right soil? Many plants and animals could have benefited from sight but didn’t “evolve eyes.” You can’t use “evolve” as an active verb. Evolution is whatever happens, without anyone guiding it or needing it. Once again we see evolutionists misusing and misunderstanding their own theory.
The fact is, each animal has the senses it needs for its place in the ecology. Everything is equipped for its role. The story should have been that starfish are more amazing than previously thought, not that they represent a missing link. Maybe the evolutionists are panicking at the release of Stephen Meyer’s best-selling book, Darwin’s Doubt, laying out the case for intelligent design as seen in the Cambrian fossil record. For a shorter explanation of the Cambrian explosion, see Illustra’s film Darwin’s Dilemma.