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Rewriting the Book on Insects

Rewriting the Book on Insects


Some years ago during the summer, I was a counselor at a small camp in southeastern Quebec. Nature interpretation was my specialty. It was dark each evening by the time the campers converged on the washroom after campfire. The lights of that building attracted all manner of creepy crawlies. Frequently at this time I would hear a shout “Moxie, Moxie — what is this thing in the washroom?”

So we would look at the specimen. If it had six legs, of course, it was an insect. There were certain things in life that one could count on, and this was one of them. If it had six legs, it was an insect. However this relationship does not hold anymore. Molecular biology, interpreted in an evolutionary context, is drastically revising many useful and reasonable biological categories.

At any age the ability to categorize or assign artifacts to appropriate mental categories, is a very important skill. In such fashion we make sense of the vast profusion of living organisms by assigning them to groupings or categories which reflect common characteristics. Carolus Linnaeus, an important early biologist, believed that the vast diversity which we see is variation on the initial body plans or themes created by God. We are able to categorize organisms because God designed them to fit logical groupings. In addition, on a more practical level, the ability to categorize organisms is useful. The characteristics which creatures in the group possess, will in all likelihood be found in newly discovered members of the group as well.

Let us consider, for example, organisms with a jointed exoskeleton (outside skeleton or tough skin to which muscles are attached). These are called arthropods. This is no insignificant group! Biologists tell us that about 85% of all known animal species are arthropods. Next we count legs. Traditionally, if the creature has six legs, we assign it to the insect class. If it has eight legs, it is a spider or a tick or similar nasty creature (chelicerate class). If it has a long body and numerous legs, it is a millipede or centipede (myriopod class), or if it has a body divided into head, thorax and abdomen, two pairs of appendages in front of the mouth, and various numbers of legs, then the creature is a crustacean. Most crustaceans live in water, either marine or freshwater. For example this group includes lobsters, shrimp and crayfish as well as waterfleas.

Many people think of insects as flying creatures and of course, most have wings and indeed do fly. Among the none-too-popular specimens without wings are lice, silverfish and hopping creatures of the forest floor called spring- tails. Moreover biologists have long considered that the non- flying springtails are the most primitive insects that we know about. Indeed they considered them to be most like an imagined ancestor for all insects. Over time, these scientists suppose, insect descendants of the ancestral type acquired wings and other variations on the insect body plan.

It is evident that insects have traditionally been distinguished by their common characteristics which include, besides exoskeleton (outside skeleton), a head, thorax and abdomen, eyes and six legs. Scientists have always assigned organisms with this collection of characteristics to the class Insecta. Evolutionists moreover have supposed that this collection of characteristics is so unique that all such organisms must be related by descent. Whether the reason for the grouping is evolution theory or common design, the end result was the same. All organisms with the above set of characteristics were considered to be insects.

Recently scientists have made use of new information in their attempts to categorize organisms (i.e. to trace lines of evolutionary descent). This involves the coded arrangement of information in DNA molecules in each species. The evolutionary expectation is that categories based on genetics will match the groupings established on the basis of obvious body form. In study after study however, this is not the case. When the two sets of data do not agree (body form compared with DNA), scientists consider that the DNA sequences provide the reliable relationship. This means that organisms which share many specific characteristics may not necessarily belong to the same group and may not necessarily be related in an evolutionary sense. A recent international study on insects has dramatically demonstrated the problem.

In a study carried out with cooperation between Italian and American scientists, DNA sequences of 13 protein coding genes from 35 organisms were compared (see Science 299 March 21/03 pp. 1887-1889). A computer program produced a branching diagram designed to show which organisms were more alike or less alike. Among the organisms involved were twenty insect species, two crustacean species and various other organisms such as an earthworm, horseshoe crab and squid. The resulting computer generated pattern of relationships looked reasonable enough at first glance.

However, on closer inspection, it turned out that the honeybee and louse were grouped with ticks (8 legged chelicerates). Moreover the springtails (flightless insects) were grouped with crustaceans like the waterflea and brine shrimp. Obviously these results were not at all what was expected! It did not take the scientists too long to decide that the honeybee and louse grouping with mites was not believable. They then eliminated twenty species from their analysis on the grounds that these showed different rates of evolution or other anomalies in the mechanism of evolution and thus yielded biased results.

The next analysis included only fifteen species. Fruit flies and moths were eliminated but among other insects, a mosquito and a flour beetle remained. Of course the springtails also remained because these were the focal point of the study. This new analysis too placed crustaceans (many legs and special antennae) closer to the insects, while the springtails were again located farther away from other six legged organisms. Although the springtail results were unexpected, scientists concluded that they could live with that result. In evolutionary terms, this conclusion suggested that the springtails had a separate origin from other six legged organisms.

This study is interesting for a number of reasons. Firstly, it is evident that scientists discard results with which they do not agree. This practice means that there is a subjective element to their conclusions. Also, the fact that time and again, similar organisms are found with very different DNA, suggests that the process of evolution is not a good explanation for similarities in form. On the other hand, many of us believe that God created insects and He did not use a process of descent to do it. Thus the DNA of various organisms, while similar in general outline, does not necessarily reflect any kind of pattern when details are considered.

An important objective in science is to derive general principles. Molecular analysis however is making taxonomy (categorizing of organisms) more and more complicated. We will soon have information overload if we don’t already. The only thing these analyses demonstrate is that evolutionary predictions don’t work. Body form and DNA sequence do not agree because the Creator was not bound to any such rules. He created according to His good pleasure, not our conception of what this should be. Meanwhile let’s not rewrite the book on what constitutes an insect. Moxie says why tamper with something that works!

July 2003

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