Lessons From the Trilobite

One of the more interesting fossils you will ever find is a fossil called a trilobite. This three-lobed ocean-going creature is actually an anthropod--relating to insects and crabs. Its closest living relative is probably the horseshoe crab although behaviorally it may have been more like a lobster or crayfish. Trilobites are one of the first animals to have lived on the earth. Beautifully preserved specimens are found in rocks believed to date back to beginning of life on the earth.

We are able to study the eye of the trilobite because it is made of the mineral calcite. Calcite is the same mineral that makes up limestone so it is quite hard. In its purest form, it is perfectly clear. Calcite possesses what is called a double index of refraction. Because of the way that the atoms in the calcite are arranged, light arriving at one angle passes undisturbed while light at another angle will be split into two beams traveling at different angles.

Trilobite In addition to being made of calcite, the trilobite eye was actually made up of a honeycomb of hexagons. There could be several thousand hexagons in the eye arranged so that light from any angle would be refracted into the animal's eye. If it came perpendicularly, the light would go straight to the back of the eye. If it came at an angle, the double index of refraction would still bring the light to the back of the eye. There is a small wall between the hexagons so that light from one hexagon does not overlap the other. When anthropods grow, they molt their outside layer. The new larger layer then hardens. The eye material would add hexagons as the animal got larger.

This kind of eye is similar to the eye of the house fly. The trilobite would be especially good at detecting motion. It also would not have a problem with near-sightedness or far-sightedness. Something an inch away or a mile away would both be in focus at the same time.

There is one problem the trilobite would have, and that is an optical problem called spherical aberration. The thickness of materials in each hexagonal lens would not be the same, and this can distort an image. In the trilobite eye, this has been solved by magnesium atoms being added to the calcite in such a way that it corrects for the aberration. Modern opticians call this a doublet.

There actually are many other special features that have been observed in various species of trilobite. Some have been found that were eyeless and probably lived in an area with no light--perhaps in very deep ocean areas. Others were mounted in ball-like structures that could be moved. Still others were positioned in such a way that the animal could bury itself in sand like a sting ray, and its eyes would still be able to look out for food or enemies. Because calcite is hard, it is preserved for us so that all this information can be experimentally produced.

There are a great many lessons to be learned from what we have briefly surveyed in this discussion of trilobite eyes. The incredible complexity and design of the eye is a tribute to God's wisdom and design in all of His creatures throughout time. In this case, however, the complexity is of special interest because the trilobite is one of the first animals to live on this planet. To talk about this complexity being the result of evolutionary forces over very long periods of time is difficult because this animal dates from the start of life on earth. The trilobites already have a sophisticated visual system when they first appear in the fossil record. The genus Fallotaspis is dated at 500 million years ago to the Cambrian period.

Darwinistic models have problems explaining the difficulties that fossils like this pose. Other proposals may be more attractive possibilities. Some of these like punctuated equilibrium offer some help but have their own set of problems. It is an exciting time to be alive. New findings, models, and explanations come out daily. When the dust settles, however, there is always another support found for the credibility of the Bible and for God's role in the creation. Reverence: "Crystal Eyes," by Richard Fortey, Natural History, October, 2000, page 68.

--John N. Clayton

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