A Review of "DARWIN'S
BLACK BOX - the
Biochemical Challenge to Evolution",
for Bios magazine; a web version of this is available at: http://www.cbs.dtu.dk/staff/dave/book-rev_text.html.
I was delighted to hear of a book written by a Biochemist, questioning whether "gradualism" could explain the origins of complexity. The problem seems pretty clear - how could one possibly explain the origin of complex, interdependent biochemical systems, with a step-by-step reductionistic approach? I have long been interested in evolution and the origins of complexity, and so was looking forward to reading Michael Behe's "DARWIN'S BLACK BOX - The Biochemical Challenge to Evolution". However, as I began to read the book, I became concerned (and frustrated) by some of the statements made (rather dogmatically) about "modern biochemistry". I feel that although Behe asks a good question - and the subject of the book has potential for some really interesting problems to be dealt with - his manner of presenting the arguments made the topic appear more translucent (and occasionally opaque) rather than clear. Many of my biologist friends tell me that few "modern biologists" believe that Darwinian gradualism on its own can fully explain evolution - and most of them agree that there are aspects of punctuated evolution mixed with the more slow gradualistic evolution. I had expected the book to deal more with this, or perhaps to discuss some of the new ideas concerning origins of complexity in terms of "self organization" systems. Instead I found the book to consist mainly of a general debunking of natural selection altogether. This review is my own personal response to Behe's "Biochemical Challenge to Evolution".
Molecular biology [or "modern biochemistry"] DOES indeed provide a very convincing basis for describing the evolution of life, at the molecular level, contrary to the central thesis of Michael Behe's book. It is the purpose of this review to have a careful look at Behe's arguments, and to point the reader towards evidence that biochemistry CAN in fact account for the origins of the complex molecular structures of life."Yet for the Darwinian theory of evolution to be true, it [modern biochemistry] has to account for the molecular structure of life. It is the purpose of this book to show that it does not." (page 25)
One could argue that Behe is invoking a conspiracy
theory from within the scientific community, on the order of "X-files".
Here's a job for agent Mulder to investigate! The scientific community
knows "the truth", but doesn't want to admit it, for fear of theistic implications.
There have already been numerous
reviews of this book, and in a sense I feel a bit hesitant to add yet
another one here, but I also feel it is important to communicate my opinion
of this book to the readers of Bios magazine (undergraduate biology majors),
especially after the release of the paperback version a few months ago
and the continual presence throughout the spring of 1998 of the hardback
version as number 1 best-seller on the Amazon.com list of evolutionary
titles (the paperback version, which came out in March of 1998, has been
climbing quite quickly within the top 20 as well). Obviously
this is a popular book. Behe's challenge should be taken seriously,
and the positive aspects as well as the negative should be exposed.
A look at Behe's arguments for "irreducible complexity"
One recurrent theme in the book is the concept of "irreducible complexity", for which the household mousetrap is used as an example. The argument goes something like this: You need at least 5 essential components for the mousetrap to work - a platform, holding bar, spring, catch, and hammer. If any of these are missing, the mousetrap fails to work. Perhaps this analogy works for things built by humans, but I think it is very dangerous and misleading to try and extend it to molecules - in this case, biochemical systems and evolution. I will not go through his 5 examples of "irreducible complexity" here. A more detailed discussion of the examples in the book can be found on the web-based version of this review. Instead I want to have a look at some of the scientific work that has been done in the last few years since the publication of "Darwin's Black Box".
What has happened in the area of biochemical evolution recently? According to Behe, there is embarrassingly little progress being made in the area of molecular evolution. So one might not expect much to have been found since his book was published in 1996. Of the approximately 4100 articles published on molecular evolution in the PubMed database (as of Sept., 1998), most (3471 or ~84% of the total) were published since 1996! I want to outline just 2 major advances in the last few months, and relate these findings to Behe's book.
The first discovery to be discussed is the finding of an RNA molecule that can catalyze nucleotide synthesis. (Unrau and Bartel, Nature, 395:260-262, 1998.) This was done by a clever modification of natural selection in a test tube. The theme of chapter 7 in "Darwin's Black Box" is basically about the complexity of synthesis of nucleotides - in particular AMP. "If there is a detailed Darwinian explanation for the production of AMP out there, no one knows what it is..." (page 161). I strongly encourage the reader to take the time to have a look at this article, as well as the "news and views" article which describes the significance of this finding (pages 223-225 of the same issue (17-Sept-98)of Nature). Using a similar method of selection, other enzymatic activities for RNA have been found, such as an ester transferase (a postulated precursor to ribosomal RNA; Chem. Biol., 5:23-34, 1998).
The second major recent discovery has to do with
the origins of the immune system. Again, Behe lays down the challenge:
look high or we can look low, in books or in journals, but the result is
the same. The scientific literature has no answers to the question
of the origin of the immune system." (page 138).
Now a clear, simple, molecular mechanism has been proposed: the immune
system we know today could have arisen due to a single insertion of a transposable
element. (A transposable element is a piece of DNA which codes for
a protein which will then bind to the DNA loop the DNA around and splice
out the DNA, and then the DNA mini-circle can be spliced into another location
of the genome. Some types of transposable elements make a copy of
the DNA first, thus duplicating themselves. ) The RAG1 and RAG2 proteins
are actually two halves of a transposase. These elements constitute
less than 5% of the DNA in yeast, roughly a third of human DNA, and nearly
all (>98%) of the DNA in lilies. In a real sense this is "selfish
DNA", but actually this ability to make copies of itself and splice together
different regions has been utilized (through natural selection) to develop
the immune system. "One might argue that such complex organisms as mammals
(and other vertebrates) can only exist thanks to an immune defense system
whose repertoire matches that of invading viruses and microorganisms (many
of which, incidentally, use DNA rearrangements to increase their antigenic
repertoire). If that is true, we may owe our existence to one transposition
event that occurred 450 million years ago..." (Nature, 394:718-719;
744-751, 1998). Once again, the reader is encouraged to seek out
the original literature and read for themselves the detailed mechanisms
proposed. My point here is merely to wave a flag and say that what
Behe had declared impossible has been obtained!
These two examples are merely a small sample of the
literally THOUSANDS of articles that have been published about the details
of molecular evolution in the past two years. It is important
to bring up these examples, because this shows a real weakness in the logic
that says "we don't know how this happened, so God must have done it!".
What happens when someone calls your bluff and actually DOES provide a
step-by-step mechanism for the gradual evolution of the immune system?
"All is dark, obscure and open to dispute when the cause of a phenomenon is not known; all is light when it is grasped."
The "Biochemical Challenge to Evolution", according to this book, is that now that "modern biochemistry has uncovered the secrets of the cell", there is "an eerie and complete silence" in the scientific literature about molecular evolution. Essentially, now that we fully understand how cells work at the molecular level, most scientists are very much aware that Darwinian evolution cannot possibly explain the complexities of life. Perhaps (grudgingly) Darwinian evolution might work at the organismal level, but it falls apart for lack of evidence at the biochemical level, according to this version.
Michael Behe's book reminds me of a "far-side" cartoon, where a scientist has filled the blackboard with equations, and then he says, in exasperation, "Then a miracle occurs!". The question is - must God necessarily be restricted in the method of creation, such that the only options are ones that science has not (yet) explained? Is it possible that God could use natural processes to create life? It is only very recently, within the last few hundred years, when scientists disproved spontaneous generation, that some theologians decided to try and hook their theology to the shifting sands of modern science - and this has been a source of problems ever since. Presently the trend of Darwin bashing is limited mainly to the U.S. - most scientists in Europe have never even HEARD of the "creationism" common in many parts of the U.S.
I want to try and put "The Biochemical Challenge of Evolution" into perspective. Behe is opposed to Darwinian evolution, but claims he's no creationist - he also realizes that there is evidence the world is older than 10,000 years. He even makes a bolder statement: "Further, I find the idea of common descent (that all organisms share a common ancestor) fairly convincing, and have no particular reason to doubt it...." (page 5). If one believes in "common descent", then this might create a bit of a puzzle in terms of the intelligent design argument. Is the "intelligent design" only visible at the molecular level, and not to be readily seen at the organismal level? If you allow for the evolution of complex systems from simpler systems in anatomy, for example, at what point could you say intervention by the Intelligent Designer must occur?
I think Behe has exaggerated the case - at the expense of the credibility of his argument, in my opinion. First, he OVERSTATES the case for our present state of knowledge. Behe claims that explaining evolution was "easy" before modern biochemistry discovered how complex life really is, and now that we have this vast amount of knowledge about how the cell works, we realize that it is simply too complex to have evolved by gradualism. If one didn't know anything about biochemistry, it sounds like we presently almost have fully solved how the cell works. Second, he UNDERSTATES the vast amount of literature on molecular evolution that can readily be found, through simple searches. For example: "Molecular evolution is not based on scientific authority. There is no publication in the scientific literature - in prestigious journals, specialty journals, or books - that describes how molecular evolution of any real, complex, biochemical system either did occur or even might have occurred." (page 185). In the five specific examples of "irreducible complexity", I entered the search terms suggested, and came up with several hundred articles about the evolution of these systems, in a matter of a few minutes. Once again - please don't take my word for it - have a look for yourself! Finally, in my admittedly biased opinion, he SETS UP A FALSE DICHOTOMY - if there are indeed complicated systems that scientists can't presently explain the origins of, then it must be that there was a "Great Designer" who is responsible.
In many senses "Darwin's Black Box" has a flavor which is similar to many of the more traditional creationists books - an appeal to ignorance of the subject matter. To someone who knows only a little bit about biochemistry, (indeed, the intended audience) this book could sound like a devastating attack on Darwinian evolution by natural selection. Unfortunately, it was quite tortuous for me to read. The subject matter has the POTENTIAL for a very good book, but I was continually frustrated by his distorted portrayal of molecular biology. It is my own opinion that, upon closer inspection, his "biochemical challenge to evolution" vaporizes to essentially a restatement of the traditional creationist attack on Darwinian gradualism: life is so complicated - it MUST been created by a divine intelligence. This is a matter of belief, either I can choose to believe that God created life, or I can choose not to believe this - but to say that science FORCES me to believe one way or the other denies my free will. "Inferring that biochemical systems were designed by an intelligent agent is a humdrum process that requires no new principles of logic or science" (page 193). Most molecular biologists would agree that many biochemical systems appear to be designed (i.e., optimized energetically, as Stuart Kauffman has put it so well)- but they would argue that it is selective pressure from "nature" or the environment which is responsible for the design. For a scientist to say that "a miracle must have happened" is not a routine (or valid scientific) explanation.
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