The National Academies (Science, Engineering, Medicine) (USA) have just published their latest book on the evolution/creationism controversy. You can download it for free on their website [Science, Evolution, and Creationism].
The book attempts to define evolution and it doesn't do a bad job of describing a minimal definition that would be acceptable—that is if you only look at the actual definition. Here it is from page 5.
Evolution consists of changes in the heritable traits of a population of organisms as successive generations replace one another. It is populations of organisms that evolve, not individual organisms.Sandwalk readers will know that this is the kind of definition that I prefer as well [What Is Evolution?]. This sort of definition is neutral with respect to mechanisms. It doesn't matter whether evolution occurs by natural selection, random genetic drift, of something else entirely. That's just as it should be because the explanation of how evolution occurs lies properly in the domain of evolutionary theory. Thus, we can say that evolution is a fact because we see it happening and we have overwhelming evidence that has happened in the past. We can be confident that it is a fact even though we may not be as certain about how it happened.
Once we start committing to an explanation we can no longer talk about facts, in many cases, since the exact mechanism of evolution is often disputed. The National Academies book begins with a wonderful description of Tiktaalik, a fossil animal that shares characteristics of both fish and primitive tetrapods. It is strong evidence in support of the evolution of tetrapods from fish and that lineage is now considered to be a well established fact.
However, it would be wrong to use Tiktaalik as support for a particular mechanism of evolution. The fossil suggests that natural selection is playing a role but random genetic drift is not ruled out. We know from other sorts of data that natural selection and random genetic drift are facts, as well as being part of evolutionary theory, but it's a good idea to draw a distinction between evolution, the process, and theories about how it occurs. This is especially true when trying to explain things to IDiots.
Unfortunately, the authors of Science, Evolution, and Creationism don't do as good a job in this regard as they should have. For example, the (reasonably correct) definition that I quoted above is found at the end of a paragraph that weakens it considerably. Here's the entire paragraph ...
If a mutation increases the survivability of an organism, that organism is likely to have more offspring than other members of the population. If the offspring inherit the mutation, the number of organisms with the advantageous trait will increase from one generation to the next. In this way, the trait — and the genetic material (DNA) responsible for the trait — will tend to become more common in a population of organisms over time. In contrast, organisms possessing a harmful or deleterious mutation are less likely to contribute their DNA to future generations, and the trait resulting from the mutation will tend to become less frequent or will be eliminated in a population. Evolution consists of changes in the heritable traits of a population of organisms as successive generations replace one another. It is populations of organisms that evolve, not individual organisms.The next paragraph then goes on to describe natural selection. There is no mention of random genetic drift anywhere in the book, although there is a passing reference to the fact that neutral mutations can be fixed. This reference is found on page 29 near the end of the book.
The net result is that evolution the process, is intimately connected to the mechanism of natural selection in this book. Readers will assume that scientists equate evolution with natural selection and use the terms interchangeably.
Why is this a problem? Well, for one thing, it's wrong. Normally that should be a good enough reason to avoid such errors, but these days there's a movement afoot to frame evolution in a way that resonates with the general public. Perhaps it's okay to define evolution as natural selection if it helps educate the average person? I object to such reasoning in the strongest possible terms. The essence of science is being honest and accurate and those goals should never be sacrificed for political gain. It may be easier to avoid confusion by not mentioning other mechanisms of evolution but the end result is that the public is not being educated correctly about evolution. You can't then turn around and complain that the public doesn't understand evolution.
The IDiots are upset about this book. They have found many ingenious ways of criticizing the contents. Here's a perfect example from Casey Luskin [The Facts about Intelligent Design: A Response to the National Academy of Sciences’ Science, Evolution, and Creationism].
I don't have the time, or the patience, to correct everything that's wrong with this article but there's one point I'd like to address. Here's what Casey Luskin says about evolution.
The NAS unscientifically elevates evolution to the status of unquestionable dogma.In the past it has been easy to show that the IDiots are either mistaken or lying when they make comments like this. I've said many times that they deliberately try to confuse people by making it seem as though evolution, the fact, is the same as natural selection, the mechanism. They know full well that there's a difference between controversies over the sufficiency of natural selection and whether evolution, per se, is overwhelmingly support by hard evidence. They know that evolution is not the same as Darwinism and attacks on Darwinism are not the same thing as attacks on evolution.
The NAS defines evolution as evolution by natural selection and claims that “[t]here is no scientific controversy about the basic facts of evolution,” asserting that evolution is “so well established that no new evidence is likely to alter” it. In doing so, the NAS treats Neo-Darwinian evolution like an unquestionable dogma, not like a science. Such proclamations from the NAS are dangerous because they threaten the prestige of the NAS as an objective and trustworthy voice advising society.
Moreover, the NAS’s claim that there is no controversy over evolution is a bluff, for there is significant scientific dissent from the view of evolution by natural selection. Leading biologist Lynn Margulis, who opposes ID, criticizes the standard Darwinian mechanism by stating that the “Darwinian claim to explain all of evolution is a popular half-truth whose lack of explicative power is compensated for only by the religious ferocity of its rhetoric.” She further observes that “new mutations don’t create new species; they create offspring that are impaired.” In 2001, biochemist Franklin Harold admitted in an Oxford University Press monograph that "there are presently no detailed Darwinian accounts of the evolution of any biochemical or cellular system, only a variety of wishful speculations.” Other scientists have gone much further.
Over 700 doctoral scientists have signed a public statement asserting their agreement that they "are skeptical of claims for the ability of random mutation and natural selection to account for the complexity of life." But what are these scientists to do when the top scientific organization in the U.S. proclaims that evolution is as unquestionable as the existence of atoms or the heliocentric model of the solar system? Clearly the NAS’s statements threaten the academic freedom of scientists to dissent from Neo-Darwinian evolution.
This rebuttal is now a bit more difficult with the publication of Science, Evolution, and Creationism. Nowhere in the book do the authors deliberately make the distinction between natural selection and evolution and nowhere do they mention any other mechanism of evolution (e.g., random genetic drift). When reading the book, most of us recognize that there are abundant, oblique, references to the fact that the authors are not stupid, but that is only apparent to scientists who know about evolution.
Casey Luskin has taken advantage of this lost opportunity on the part of the National Academies to make it look like they are being dogmatic and forcing everyone to accept Darwinism. When I decided to write about Luskin's silly article, I thought it would be easy to refute what he was saying by referring back to the book. I thought the book would make it clear that evolution is not the same as natural selection. Unfortunately, there's nothing I can quote from the book that explicitly makes that point even though it's there implicitly. That's a missed opportunity that I hope can be remedied in future printings.