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Wednesday, April 25, 2007

Guest Book Review: Darwin on Trial

A friend of mine who is a PhD in microbiology recently read "Darwin On Trial" and he was kind enough to write a review about it. This book was recommended to me as one of the best critiques of evolutionary theory. Let's see if a practicing scientist agrees:

Darwin on Trial

Phillip E. Johnson’s “Darwin on Trial” attempts to show that the concept of evolution based on natural selection is not a true scientific theory, as it is based on logical deduction rather than demonstrated empirically by the scientific method. In addition, he attempts to show that the logical deductions are based on evidence, such as the fossil record, that fail to provide proof of gradual evolution of organisms over time. Superficially, this appears sensible, but the author is making demands of science that are impossible, and then denouncing the theory of evolution once he has shown that these demands cannot be met.

One example cited by the author is the inability of scientists to demonstrate in the laboratory that one species can diverge and give rise to two distinct, non-interbreeding species. Based on what is known about speciation, this may require hundreds of thousands, if not millions, of years. It is not expected that laboratory experiments are going to produce speciation events. Another example is given for animal breeders, who have been selectively breeding animals for centuries, yet still have not been able to produce a speciation event. A few centuries of selective breeding are not expected to give rise to a speciation event, and breeders obviously have not had the goal of speciation in mind in the first place. It is these types of impossible experimental demands that Johnson uses throughout the book to demonstrate that Darwinian evolution cannot be proven or falsified. The reality is that these types of experiments cannot be performed because all aspects of nature cannot be captured in a laboratory setting. These are insufficient grounds for denouncing the theory of evolution.

There are many scientific fields that rely upon logical deduction to support a given theory. Evolution is but one. Plate tectonics is a scientific theory of geology that has been developed to explain the observed evidence that the Earth’s lithosphere has undergone large scale motions over time. Like evolution, the theory is based on evidence discovered by geologists, and because of the scale and time constraints of the phenomena in question, cannot be tested in the laboratory. Science does not have the means of recreating a planet, and as such, there is no way to definitively prove or disprove that plate tectonics gave rise to the architecture of the earth as we now see it. However, the evidence collected by geologists is so convincing that it is logical to deduce that plate tectonics has occurred. This is also the case for the theory of evolution: the myriad evidence has led scientists to deduce that organisms are not static, but change over time upon adaptation to selective pressures.

One source of evidence is repeatedly attacked by Johnson; namely, the fossil record. Fossilization is a rare event, to be certain. It is far more likely that the remains of organisms will be rapidly decomposed as opposed to fossilized. As a result, the fossil record is composed of organisms that were widespread and existed (or still currently exist) for a long period of time during the earth’s history. It should come as no surprise that there are significant gaps in the fossil record. Johnson seems to be under the impression that the fossil record is a neat and tidy compendium of all life that has existed on earth. In reality, the fossil record supplies researchers with an exceedingly minute sampling of organisms that have existed on earth. This is likely the reason that intermediate links or transitional fossils, those that “bridge the gap” between two closely related species, are some of the most rare of fossils. If transitional forms are ephemeral, their absence in the fossil record is expected. Johnson desperately tries to convince the reader that the lack of transitional fossils is grounds for dismissing the theory of evolution. If the fossil record does not show it, it must not have happened. Unfortunately for Johnson, the number of transitional fossils has increased since his book was first published. A very good resource for transitional fossils is The TalkOrigins Archive ( It is very obvious that Johnson has overlooked these fossils to add validity to his argument.

Perhaps the gravest error that Johnson made in writing “Darwin on Trial” is the explanation that laboratory science cannot establish a mechanism for evolution. He then goes on to explain that “microevolution”, or mutations that slightly modify members of a given species, does occur and is even accepted among creation-scientists. Microevolution occurs when random mutations give rise to a heterogeneous population of organisms that are similar, but differ slightly in their outward phenotypic traits. When a selective pressure such as a change in the environment occurs, some members of the population will be able to survive the change, and some will not. Those that survive will live on to reproduce, thereby passing down the genetic traits that allowed for their own survival, and the overall population will change, with those individuals that were able to survive and reproduce under the new selective pressure becoming the sole members of the species. What Johnson fails to see is that this is evolution. Whether you choose to give it a prefix like “micro” or claim that it is insignificant does not change the fact that this is exactly what evolution is, and the mechanism by which organisms evolve. That being the case, it has been possible for scientist to document the evolution of such organisms as certain insects, which have rapidly become resistant to pesticides, or microbes such as bacteria and viruses, which have become resistant to many antibiotics and pharmaceutical therapeutics. There is no reason to think that these types of changes, which in actuality are quite drastic, cannot be extended over millions of years to give rise to speciation events, or “macroevolution”. In my opinion, to embrace microevolution is to embrace evolution, period. Johnson simply tries to sidestep the issue by using the term microevolution. If microevolution can occur, what biological barriers exist to prevent macroevolution? The bottom line is that both qualify as evolution, and Johnson is wrong in stating that the mechanism of evolution has not been discovered by science.

One of the more disturbing aspects of Johnson’s book is that he tries to give the reader the impression that many well-renowned scientists are aware that the theory of evolution is significantly flawed, yet try to “cover-up” the condemning evidence so that they can safeguard their sacred theory. He portrays scientists as a secular group with the sole aim of disproving the existence of a divine being or god capable of creating life. In every case in his book, when he brings up criticisms about the theory of evolution, those criticisms come from scientists that support the theory. Further, if Johnson was able to procure these statements, what is stopping the general public from obtaining them? Nothing. Read the research notes and pull out the original articles, or simply do some of your own research on the topic.

Scientists are not brainwashed zealots that accept everything they are told, but rather challenge current theory when new evidence comes to light. By no means is the theory of evolution static; it is constantly being changed and altered as more evidence accumulates. Do scientists become protective when people challenge evolution? I know I do. This is not because I am trying to hide anything or secretly want to discredit the existence of a divine being, but because evolution is a theory that is consistently under attack by religious groups who want to see it banned from existence. I strongly believe that Johnson’s portrayal of scientists is fantasy, but I do think that it is a very accurate description of the type of people he is trying to represent: creationists.

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