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Understanding Michael Behe's edge of evolution

It's been about twenty years since Intelligent Design Creationism rose to prominence. Just last week the Center for Science and Culture celebrated it's 20th birthday [Twenty Years Ago Today, Did This Change the Evolution Debate Forever?]. In all that time, the best that ID proponents can come up with is some work by Michael Behe that attempts to discredit evolution.The first book by Behe was Darwin's Black Box where he developed the notion of irreducible complexity. The definition of irreducible complexity has changed over the years but the basic idea is that some biological structures are very complex and the removal of any one part will render the complex nonfunctional. This presents an enormous problem for evolution, according to Behe, because all the presumptive intermediates will be nonfunctional.

The conclusion is that it's impossible to evolve an irreducibly complex structure. Evolutionary biologists have no problem accepting the existence of irreducibly complex structures. They see them all the time. What they object to is the idea that irreducibly complex structures cannot have arisen by evolution. Behe's conclusion has been shown to be false and he has admitted on multiple occasions that irreducibly complex structures can arise by purely natural means (evolution).

So much for that objection to evolution. (Note that ID proponents are incapable of providing positive evidence of intelligent design. The best they can do is to try and discredit the best explanation for the appearance of design; namely, evolution.)

Today I want to talk about Behe's second book since ID proponents are even more confused about that. In The Edge of Evolution, Behe argues that some mutation events are so improbable that they will never occur in any species at any time over the past three billion years. This is the "edge" of evolution.

The basic idea is this. Imagine that two mutations have to occur at the same time in order to confer a benefit. Since the mutation frequency is about 10-10, it follows that the probability of a double mutation is about 10-20. Behe actually uses different numbers that give a higher probability but that's not relevant here. I prefer to use the correct values. They make his case even better.

Behe looks at what he thinks is an example of such an event; namely, the evolution of chloroquine resistance in malaria parasites (Plasmodium falciparum). He shows that, given the size of the Plasmodium population and the frequency of reproduction, this species can evolve chloroquine resistance by a mechanism involving simultaneous double mutations. His calculation are roughly correct. This mechanism is possible in Plasmodium.

Behe concludes that this kind of event, which he calls a "chloroquine-complexity cluster" (CCC) is well within the edge of evolution, at least for some species. However, if instead of two simultaneous mutations, what if organisms needed FOUR simultaneous mutations? The probability of this event is 10-40! Such a "double CCC" is never going to happen in any lineage. It's the edge of evolution.

Here's how he describes it in The Edge of Evolution (p. 63).
Put more pointedly, a double CCC is a reasonable first place to draw a tentative line marking the edge of evolution for all of life on earth. We would not expect such an event to happen in all of the organisms that have ever lived on this planet. So if we do find features of life that would have required a double CCC or more, then we can infer that they likely did not arise by a Darwinian process.

As we'll see, life is bursting with such features.
Behe is correct. If an evolutionary event requires that four mutations occur simultaneously then it's never going to happen. If we were ever able to prove that such an event had actually happened multiple times then evolutionary theory would be in trouble.

Behe assumes that such events have actually happened so he concluded that evolution cannot explain them. The only alternative is Intelligent Design Creationism. Behe is wrong about that. Life is not "bursting" with such features. In fact, none have ever been discovered.

The flaw in the argument is his conclusion that certain events can only be explained by multiple mutations occurring simultaneously. As it turns out, he was wrong about his main example, chloroquine resistance in Plasmodium. Several workers have shown that multiple mutations in the same gene are required (more than two) but these arose one-at-a-time in a stepwise manner. Some of them were neutral and some of them were slightly deleterious but persisted in the population because they escaped negative selection. Thus, chloroquine resistance has arisen mutliple times in Plasmodium because simultaneous multiple mutations were not required.

This is exactly what evolutionary biologists were expecting. No "edge of evolution" has been crossed because mutations can accumulate sequentially even though the effect might not be expressed until several of them have accumulated.

Do Intelligent Design Creationists understand Behe's argument and why it is flawed? The answer, of course, is "no." Intelligent Design Creationists have a great deal of difficulty dealing with complex arguments that require an understanding of evolution. Most of them can't even properly explain the main arguments of their leaders (e.g. Michael Behe) let alone the objections of their critics.

I was prompted to write this post by a recent article in Evolution News & Views (sic) written by Sarah Chaffee1 [Students, Scientism, and Straw Men]. It was a criticism of something that Barbara King wrote earlier. I was interested in the example that Sarah Chaffee used to promote Intelligent Design Creationism ...
If King really believes science is about continuous corrections and questions, she should be friendlier to teaching the scientific controversy over evolution, which attempts to do just that. A growing number of scientists hold that natural selection acting on random mutations cannot fully account for the diversity of life.

In The Edge of Evolution, biochemist Michael Behe examines mutations necessary to develop chloroquine resistance by malaria parasites, and concludes that two simultaneous mutations is the most evolution can accomplish. Furthermore, based on population sizes and frequency of mutations arising, he says, "No mutation that is of the same complexity as chloroquine resistance in malaria arose by Darwinian evolution in the line leading to humans in the past ten million years."

Engaging with the evidence is important -- and so is freedom to discuss dissenting ideas.
The remarkable thing about this excerpt is that she correctly references a small part of Behe's argument. Behe did show that a CCC is possible in malaria parasites and even though a double CCC represents the edge of evolution he does present a convincing argument that a single CCC is highly improbable in humans. He did NOT show that two simultaneous mutations were necessary to develop chloroquine resistance. The scientific evidence shows conclusively that a CCC didn't happen in Plasmodium.

Unfortunately, Sarah Chaffee leaves out the most important part of Behe's argument. There's no disagreement among evolutionary biologists about the low probability of simultaneous mutations. They all agree with Behe on that part of his argument. The disagreement is over the second, and most important, part of Behe's argument—the part where he says there are many examples of features that could only be explained by evolution if there were multiple simultaneous mutations.

That's the part that requires "engaging with evidence." I agree with Sarah Chaffee that engaging with evidence is important. There's no evidence that features requiring multiple simultaneous mutations are common in the history of life. Instead, all examples of multiple mutations can be explained by sequential accumulation of a series of mutations. This is well within the edge of evolution.

It would be nice if Intelligent Design Creationists would learn more about their own "theory" and it would be even nicer if they could start to deal with scientific evidence. That's the proper way to engage in discussions about dissenting ideas.

You would think that, after twenty years, ID proponents would have learned how to do this but I guess it's impossible. If they really understood their own arguments and started engaging with the evidence, they wouldn't be Intelligent Design Creationists.

For more information and discussion, check out the links below.

On the irrelevance of Michael Behe
Michael Behe's final thoughts on the edge of evolution
Understanding Michael Behe
CCC's and the edge of evolution
Understanding Mutation Rates and Evolution
The Edge of Evolution
Evolution in Action and Michael Behe's Reaction
Mutations and Complex Adaptations
Blown Out of the Water
Joe Thornton vs Michael Behe
Irreducible Compexity
Defining Irreducible Complexity
Another Bad Review of The Edge of Evolution


1. Sarah Chaffee is the Program Officer in Education and Public Policy at the Center for Science and Culture in Seattle, Washington (USA). She has a B.A. degree in "Government" from Patrick Henry College. Here's what's on the college's website ...
The College is, and shall always remain, a Christian institution dedicated to bringing honor and glory to the Lord Jesus Christ in all of its activities. Each trustee, officer, faculty member, and student of the College, as well as all other employees and agents of the College as may be specified by resolution of the Board of Trustees, shall fully and enthusiastically subscribe to the following Statement of Faith:

There is one God, eternally existent in three Persons Father, Son, and Holy Spirit.

God is Spirit, and those who worship Him must worship Him in Spirit and in truth.

Jesus Christ, born of a virgin, is God come in the flesh.

The Bible in its entirety (all 66 books of the Old and New Testaments) is the inspired Word of God, inerrant in its original autographs, and the only infallible and sufficient authority for faith and Christian living.

Man is by nature sinful and is inherently in need of salvation, which is exclusively found by faith alone in Jesus Christ and His shed blood.

Christ's death provides substitutionary atonement for our sins.

Personal salvation comes to mankind by grace through faith.

Jesus Christ literally rose bodily from the dead.

Jesus Christ literally will come to earth again in the Second Advent.

Satan exists as a personal, malevolent being who acts as tempter and accuser, for whom Hell, the place of eternal punishment, was prepared, where all who die outside of Christ shall be confined in conscious torment for eternity.


This post first appeared on Sandwalk, please read the originial post: here

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Understanding Michael Behe's edge of evolution

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