Evolution in Hawaii?
click here for printer-friendly version
Q. Doesn't the well documented evolution of a new species of wallaby in Hawaii provide some excellent support for the evolutionary theory of punctuated equilibrium?
A. How one interprets evidence is always going to be greatly effected by ones presuppositions. The example of the rapid "evolution" of what is known as the Kalihi Rock Wallaby on the island of Oahu, Hawaii is a textbook example of this principle. To demonstrate this, it's important to first explain the issues involved in this interesting situation.
First, let's consider the Kalihi Rock Wallaby. An article titled "Instant Evolution" was published in 1982.* "How the wallaby population got to Hawaii in the first place is well known. The animals are all descendants of a single pair of Australian wallabies that fled from a Hawaiian zoo in 1916. . . , the wallabies are now estimated to have grown to several hundred in number." (In the 21 years since 1982 the population is probably even larger today.) What is strange is that the Hawaiian wallabies are very different in color and size from the Australian wallabies of today.
The scientist studying these wallabies, James Lazell, Jr., offered two possible explanations. One is known as the "founder effect." Since the entire island population descended from the same pair, any peculiar genetic traits the escaped pair possessed would be uniformly passed on to all their succeeding generations. In other words, if the wallabies that escaped from the Hawaiian zoo happened to be smaller and lighter than the average wallaby, all their descendants on the island of Oahu, being isolated from the wallabies in Australia, would be smaller and lighter than the average Australian wallabies. The second possibility Lazell noted was this.
The creatures' physiology might simply be the result of remarkably rapid evolution. Those wallabies who were smaller and lighter in color--and thus better suited to the Hawaiian environment--would have a better chance at survival and reproduction. If (this) is the case, the wallabies' adaptation to their new environment was not only swift but extraordinarily thorough. Lazell reports that not only did the animals' external appearance change, so did the amino acid structure of at least one of their liver enzymes, which would have helped them safely feed on otherwise toxic plants on Oahu. The question remains: how did the wallabies evolve in what amounts to a mere eye blink in time? . . . Says Lazell, "To evolve into an entirely new species in only sixty generations . . . that's pretty spectacular."
There are three important observations to note concerning Lazell's explanations.
1) Designating a population of organisms a new "species" is an arbitrary assignment on the part of the scientist. 2) The possibility of a "founder effect" being the cause of the Hawaiian wallaby's different physiology cannot be ruled out. 3) The statement that "the amino acid structure of at least one of their liver enzymes" changed, i.e. mutated, can only be speculation on Lazell's part. Later in this article, we'll consider the possibility that some liver enzyme/s mutated.
The second issue we need to consider is what is punctuated equilibrium? The late Stephen Jay Gould was a major proponent of this evolutionary hypothesis. In 1979 (120 years after The Origin of Species was published) Steven Stanley published Macroevolution, a major work supporting punctuated equilibrium. In Macroevolution Stanley states, "The known fossil record fails to document a single example of phyletic evolution accomplishing a major morphologic transition and hence offers no evidence that the gradualistic model can be valid (pg. 39)." And the situation has not changed over the last 25 years. There simply are no fossils of transitional forms, "missing links," to verify the explanation that, e.g. wormlike animals evolved into clams and crabs and ultimately fish, etc., or that fish evolved into land animals.
With no evidence in the fossil record to demonstrate the transition of creatures from one major form to another, evolutionary scientists (paleontologists in particular) have proposed this phenomenon called punctuated equilibrium. The term is fairly self-descriptive. The proposal is that over the vast majority of time, evolution essentially does not occur, i.e. the diversity of life remains in a general state of equilibrium. However, this state of equilibrium is infrequently punctuated by a flurry of structural changes in certain forms of life, and new categories of living organisms burst onto the scene. An example would be the development of the complex shapes and arrangements of the bones of the terrestrial vertebrate forelimb. From 3 small bones in a fish's fin (which were similar in structure to simple vertebrae) the humerus (the single upper arm bone), radius and ulna (the two lower arm bones) are believed to have formed. These arm bones, and the attendant muscles and ligaments, enabled the transition from swimming in water (fish) to crawling on land (amphibians/reptiles). This understanding is held in spite of a complete lack of evidence showing anything like the bones of the fish's fin changing step by step into the bones of an arm. The hypothesis of punctuated equilibrium then explains that the step by step changes can't be found because they did not exist. At the "punctuation point" in history, massive mutations must have occurred in the crucial fish population. Such mutations were detrimental to most individuals, but in the case of one--actually it would have to be two, a male and female--the structural changes produced functional arms! These arms were very advantageous, and from these "lucky" mutants, the entire realm of terrestrial vertebrates evolved.
It is obvious that such changes from "fins to fingers" involve large amounts of added genetic information. Information encoded in the DNA that must instruct the developing embryo how to grow the bones, ligaments, muscles, tendons, circulatory and nervous tissues required for an arm--actually two pairs, front and rear--to function in a coordinated fashion. Punctuated equilibrium requires that large amounts of genetic information spontaneously, by chance, be generated in some individual/s. The mutations result in major increases in the complexity of the structure of the organism's form, and these changes, being advantageous, are passed on to increasing numbers of surviving offspring which look and have capabilities that are quite different from their grandparents.
Now consider the example of the Kalihi Rock Wallaby. Its apparent change in size and color in no way represents an increase in genetic information producing an increase in the complexity of the animal's form. The more interesting and significant difference between the Hawaiian and Australian wallabies is the Hawaiian wallaby's ability to eat plants poisonous to an Australian wallaby. Lazell claims that some liver enzyme/s changed. I have searched the literature extensively (so I readily admit, documentation may exist which I simply did not find); it is not known why the plants on Oahu are not toxic to the Hawaiian wallabies. It could be they have developed immunity to the toxin due to increased production of antibodies which combat the poison. That does not qualify as an increase in genetic information any more than dwarfism or gigantism. It is more likely, however, that the cause is the mutation of a liver enzyme as Lazell suggests. But what happens in such instances is the mutation causes the enzyme to lose its ability to function. The development of antibiotic resistance in bacteria is a common example of this phenomenon. Poisonous foods are usually poisonous as a result of some toxic by-product they release when digested. If some liver enzyme of the Hawaiian wallaby mutated so that it no longer metabolizes the substance/s in the Hawaiian plants that produce poisonous by-products, it was a very beneficial mutation to the wallaby, but it is not because of some new genetic information. In fact, beneficial as it may be, the wallaby lost some information. It is genetically less complex than its ancestors. Therefore, although the changes occurred so rapidly that they were, in Lazell's words, "pretty spectacular," the changes which have occurred between the Hawaiian and Australian wallaby do not constitute the kind of evidence required to support the hypothesis of punctuated equilibrium.
If someone already presupposes the truth of evolution and punctuated equilibrium in particular, it is easy to see how they would quickly interpret the example of the Kalihi Rock Wallaby as evidence for their belief. The focus is on the rapidity of change in the organism. However, given what punctuated equilibrium entails, the example of the Hawaiian wallaby does not support the punctuated equilibrium model for evolution. BUT, amazingly (!) given a presupposition that the entire diversity of life on earth has resulted from adaptations of all the kinds that God created only thousands (not millions) of years ago, the example of the Hawaiian wallaby can be interpreted in a radically different way. In fact, the Kalihi Rock Wallaby is an excellent example of what is predicted by a creation model for the production of new species--very rapid adaptation of the wallaby kind resulting in a new species of wallaby ("species" being a very subjective category assigned by some scientists.) The new species is better suited to survive in its peculiar environment than its "down under" cousins, but it possesses no new genetic information. The Kalihi Rock Wallaby is still just a wallaby, so . . . "Gooday Mate!" . . . or is it "Aloha!"
*Quotations are from the article, "Instant Evolution" in Science Digest, (July 1982) 90:7, pg. 18.
To ask Ben a question, email him at firstname.lastname@example.org