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Book Review : Evolution Question and Answer

<i> Dembart is a Times editorial writer. </i>

Evolution: A Theory in Crisis by Michael Denton (Adler & Adler: $19.95)

In the 16th Century, Nicholas Copernicus took the Earth out of the center of the universe. In the 19th Century, Charles Darwin removed humanity from its special place among living things. Perhaps more than any other intellectual achievements, these two discoveries profoundly and irrevocably changed people’s basic understanding of themselves and of their relationship to the world.

But though the basic ideas of Copernicus, Darwin and other great scientists were correct, they did not have all of the details right. So the fact that some of the details are wrong does not necessarily invalidate all of a scientist’s theory. Copernicus correctly understood that the Earth moved and the sun was stationary. He incorrectly believed that the orbits of the Earth and other planets were circular.

In the century after Copernicus, Johann Kepler discovered the three laws of planetary motion, an extraordinary advance that validated the Copernican model of the solar system and set the stage for Isaac Newton’s work. As a result, Kepler is remembered as a founder of modern astronomy and physics.

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Kepler’s Mistake

And yet, Kepler believed that there were six planets--the Earth and five others--which, he thought, corresponded to the five regular polyhedrons of geometry. But this mistake is irrelevant to the genius of Kepler’s basic idea that the planets moved around the sun in ellipses rather than in circles.

While few people still worry about the fact that the Earth does indeed go around the sun and not vice versa, the natural evolution of living forms from simple to complex continues to trouble many, including Michael Denton, an Australian medical doctor and microbiologist who makes the mistake of dismissing Darwin’s theory because Darwin got some of the details wrong. We now know that natural selection may not be the full explanation for how evolution takes place. But the fact of evolution is beyond dispute.

Denton’s book displays a vast ignorance about Darwin, evolution and science in general. Simply put, his conclusion that evolution “is still, as it was in Darwin’s time, a highly speculative hypothesis entirely without direct factual support” is absurd.

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None of Denton’s arguments are new. He contends, as many including Darwin knew, that the fossil record is incomplete, that intermediate forms are lacking and that no one ever saw one species turning into another. He acknowledges that there may be what he calls microevolution--insects developing a resistance to DDT, for example--but he argues that it’s a far cry from that to the notion of mice evolving into elephants.

But macroevolution--one species turning into another--is the sum of all of the microevolutionary changes that occur over millennia. No one has ever seen it happen because no one lives on that time scale. And yet the evidence is all around us. The hemoglobin molecules in human beings and chimpanzees are identical, but they are different from the hemoglobin molecules in sharks, gorillas and chickens. Throughout nature, the closer animals appear to be, the more similar are their hemoglobin molecules and other proteins. How can that be explained except by evolution?

Fossil Evidence

The fossil record itself can never be complete. But it is perfectly consistent. Whenever a stratum of rock is carbon-dated to the Triassic period, for example, the bones of dinosaurs and not horses will be found in it. Each new finding supports the conclusion and reinforces it.

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Far from Denton’s assertion that no evidence has been found to support evolution, every shred of evidence for more than 100 years has done just that.

When Darwin published “The Origin of Species” in 1859, he didn’t have a clue about the mechanism by which evolution takes place. It was not until later that Gregor Mendel founded the science of genetics and posited the gene as the unit of heredity, a mechanism that fit perfectly with the theory of evolution. And it was not until more than half a century after that that James Watson and Francis Crick unraveled the functioning of DNA, which explained the phenomenon of evolution on a molecular basis.

Genetic information is contained and conveyed by the sequence of chemicals in the DNA. When the sequence changes, the organism can change. That is how evolution occurs. Investigations of the last 20 years show that molecular changes follow the same pattern as observable changes in living things and in fossils. It would have been impossible to predict that Darwin’s ideas would find such powerful support on the molecular level.

Denton’s criticisms of evolution are nothing more nor less than creationism without a creator. There is much discussion today among reputable scientists about exactly how evolution takes place, but that, too, is inherent in the nature of science. Is evolutionary change a slow, continuous process, or does it occur in fits and starts? The fact that no one knows the answer does not mean, as Denton would have us believe, that the idea of evolution itself is wrong and that biologists are struggling to keep their sinking ship afloat.

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Nor is it clear whether the changes in organisms occur randomly, as Darwin believed, or whether some changes are more likely to occur than others. Biologists continually are proposing and testing new hypotheses, some of which gain support and some of which are discarded.

The theory of evolution is one of the greatest accomplishments of the human mind. Paleontologists and microbiologists are filling in the gaps in the evidence all of the time. The theory is not in crisis, as Denton’s subtitle asserts. Rather, it is the basis for understanding biology. It is no more in doubt than the once-revolutionary notion that the Earth goes around the sun.


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