(I am taking some time off from new blog posts. Until I begin posting again, which should not be more than a couple of weeks, I will repost some very early ones, updated if necessary. Today’s one is from February 17, 2005.)

A commenter to a previous posting raised an interesting perspective that requires a fresh posting, because it reflects a commonly held view about how the validity of scientific theories get established.

The commenter says:

A scientist cannot be certain about a theory until that theory has truly been tested, and thus far, I am unaware of our having observed the evolution of one species from another species. Perhaps, in time, we will observe this, at which point the theory will have been verified. But until then, Evolution is merely a theory and a model.

While we may have the opportunity to test Evolution as time passes, it is very highly doubtful that we will ever be able to test any of the various theories for the origins of the Universe.

I would like to address just two points: What does it mean to “test” a theory? And can scientists ever “verify” a theory and “be certain” about it?
[Read more…]

In a recent discussion on a listserv for physics teachers, someone strongly recommended the book The Politically Incorrect Guide to Science by Tom Bethell, saying that it exposed how mainstream science was suppressing some ideas for non-science reasons, in particular how the great weaknesses of evolutionary theory were being hidden.

I had not read this book myself but these kinds of arguments are familiar to me and Bethell had written an article describing his own book. It struck me as extraordinarily shallow, rehashing arguments that have long been discredited, and invoking misleading (and old) chestnuts about evolution occurring only by chance, and missing transitional forms, etc. In fact, he seemed to have drawn his arguments against evolution from the playbook of the intelligent design creationists, in particular Jonathan Wells’ book Icons of Evolution.

He even made the argument that the only thing that has been seen is ‘microevolution’ (small changes within species) and not macroevolution (change from one species to another). But the distinction drawn between micro- and macroevolution is untenable, since it has long been realized that there is a large overlap between varieties within species and between species as a whole, making the drawing of such distinctions difficult. Darwin himself pointed this out in his On the Origin of Species (chapter II), where he emphasized how difficult it was for even experts to classify whether animals were varieties within a single species or different species.

It is amazing that in this day and age people like Bethell still bring up Haeckel’s embryos. Modern biologists don’t take Haeckel’s misleading sketches seriously anymore since his theory was discredited more than a hundred years ago and only intelligent design creationists (IDC) keep bringing it up repeatedly to argue that scientists falsify things in order to buttress the case for evolution. In the documentary A Flock of Dodos IDC advocate John Calvert talks about how biology textbooks use Haeckel’s figures to mislead children but when asked to show this, thumbs through some textbooks and cannot find any examples. He had simply accepted this folklore uncritically. What use Haeckel has now is purely pedagogical.

The Haeckel case is analogous to someone finding that the Bohr model of the atom is still being taught in middle school science textbooks, “discovering” that Bohr’s model violates Maxwell’s laws of electromagnetism, and thus concluding that quantum mechanics is wrong and that children are being misled into accepting it. Quantum mechanics has come a long way since the Bohr atom and does not depend on it, just like evolutionary biology and Haeckel’s embryos. To keep bringing it up is a sign of desperation

Bethell’s argument about the fact that no one has seen half-bats and that therefore step-by-step evolution could not have occurred, reminds me of those people who say that it is absurd that an electron can go through two slits or that twins age differently based on their speeds. After all, has anyone actually SEEN an electron go through two slits? Has anyone actually SEEN twins age differently? If we haven’t seen such things directly, they must not occur, right? I have described earlier how incomplete the fossil record is, because fossilization is extremely unlikely, and how arguments that depend on the existence of gaps in the fossil record can never be satisfied because new gaps can always be created.

As I have said in this series on evolution, to really appreciate the theory one has to get beyond the simple minded rhetoric of the kind that Bethell indulges in and look at the underlying details and the mathematics. The question of whether evolution is a “fact” is a red herring. “Theory” and “fact” are fluid terms in science. What is true is that the fully developed theory of evolution, known as the neo-Darwinian synthesis, is the most productive and useful theory in biology today, and forms the basis of almost all research in that field.

People who dislike the theory of evolution often point to the petition that the Discovery Institute (DI), the main driver of Intelligent Design Creationism (IDC), put out signed by 700 people that says: “We are skeptical of claims for the ability of random mutation and natural selection to account for the complexity of life. Careful examination of the evidence for Darwinian theory should be encouraged.” Such people cite this as evidence that the theory is weak and then ask: “Why are so many scientists jumping off the evolution band wagon?”

But scientists are taught to be skeptical and to examine carefully the evidence for any theory. And if a theory (like evolution) challenges their religious beliefs, they are likely to be even more skeptical of it. That is a natural human tendency. It does not take any effort for a mathematician or physicist or philosopher to say she is skeptical of evolution, just as it does not cost any biologist anything to say that he is skeptical of the big-bang. After all, in each case, they are not personally working with that theory and are unlikely to know anything about it in any detail and thus can let other factors have a greater influence. As of the time when there were 400 people who had signed on, about 80% were not even biologists. (The story of one religious scientist who signed on to the Discovery Institute statement and only later realized what was going on can be read here.)

Another problem with the petition wording is that although Darwin proposed the mutation and natural selection mechanism, developments since then have added other mechanisms such as gene flow and genetic drift, so even a biologist who sees no problem with evolution would agree that mutation and natural selection alone are not sufficient.

I personally am skeptical of ANY theory in ANY field as being the last word (or the ‘truth’) on the subject because the history of science teaches us that scientific theories have always been provisional. So for me the DI statement itself is nothing more than a platitude. The fundamental issue is whether the biological community feels that evolution is in a crisis, and as far as I am aware, the biological science community does not think so and continues to use that theory as the foundation for their work. So these kinds of statements are just meaningless. When biologists start using alternative theories to generate predictions and start getting positive results, then we can take those other theories seriously.

It is important to realize that despite so many years of pushing intelligent design creationism, the people at the Discovery Institute have not been able to generate even one prediction, let alone do any experiments to investigate their theory. What they are doing is not science, it is lobbying and public relations.

Statements like the ones put out by the Discovery Institute on evolution are, however, useful as indicators of what people desire or yearn for.

For example, I am skeptical of the idea of dark matter as the explanation for the anomalous velocity distribution of stars on the arms of spiral galaxies. Why? Mostly for aesthetic reasons. It seems a bit contrived to me and the idea of huge amounts of matter surrounding us that we cannot detect reminds me uncomfortably of the arguments for the ether before Einstein’s theory showed that the ether was a redundant concept.

I am hoping that a nicer theory than dark matter comes along and I know I am not alone in feeling this way and that other card-carrying physicists share my view. So if someone handed me a petition saying that I was skeptical of the theory of dark matter and would like the evidence for it to be examined carefully, that statement’s content would not be objectionable to me. I would totally agree.

But I would not sign because it is pointless. I have not done any real work to support my misgivings. I have not developed an alternative theory, generated hypotheses, made predictions, or explained any existing data. Physicists who actually work on the spiral galaxy problem (even if they were completely outnumbered by the people who sign a petition dismissing dark matter theory) would be perfectly justified in ignoring me and any other physicists who sign such a petition in the absence of any substantive counter-theory.

What the DI petition on evolution tells us is that there are about 700 people who wish and hope that a theory more congenial to them than evolution comes along. That’s fair enough but hardly major news. They have every right to feel that way and to say so. But it is by no means a measure of the merits of the theory, however many people sign on to it, and it is dishonest of the Discovery Institute to make such a claim.

Bethell’s thesis that the scientific community is conspiring to suppress the truth about the weaknesses of evolution is silly. Given that the US has high levels of religiosity and public skepticism about evolution and widespread unease that evolution is undermining religious beliefs, any scientist who found good evidence for special creation would be deluged with funding from both government and private sources and receive high visibility and acclaim. Furthermore, such a discovery would open up vast new areas of research. In such a climate, why would any scientist not publish findings that provided evidence for special creation?

People like Bethell are trying to achieve by public relations what they cannot do using science. They are not the first to try to do this and will not be the last. But they will fail, just like their predecessors.

POST SCRIPT: The insanity of the employer-based health care system

This question posed at a Democratic presidential candidates forum illustrates perfectly why we need a single-payer, universal health care system.