Pharyngula

Behe’s Edge of Evolution, part I

I peeked.

I was reading Michael Behe’s new book, The Edge of Evolution, and I was several chapters into it. All he seemed to be saying was that evolution has limits, limits, limits, and those limits are so restrictive that you can’t get from there to here, and he was repeating it over and over, in this tediously chipper narrative voice. Behe insisted that he accepted common descent, though, and acknowledged all this evidence that, for instance, chimpanzees and humans are related by common descent, while saying that it was impossible for them to have evolved naturally from one to the other. So I was getting awfully curious to learn how they were linked by descent while evolution was impossible, and I jumped ahead to the end of the book.

“That can’t be right,” I thought to myself.

Then I flipped quickly through the last chapters.

It’s true. Nowhere in the entire book does he offer a mechanism to resolve this disconnect. He claims things were “designed”, but doesn’t explain by who, how, or when, and doesn’t even give a clear picture of what parts of evolution are designed, and which aren’t. It’s nothing but one long and almost entirely fallacious gripe about the insufficiency of natural mechanisms.

I tell you, it made it terribly hard to go back to where I left off and continue my agonizing plod through the book, knowing that there wasn’t going to be any payoff. There isn’t so much as a forlorn whiff of a hypothesis, not one experimental test, not even a suggestion about what Behe’s colleagues could do in their labs or in the field to use or evaluate his claims—just this unrelentingly negative assessment of most of biology, and this weirdly cocky confidence that he has discovered new mathematical principles that disprove evolution. That really has to be the bottom line in this review, that if you’re looking for a clear statement of the principles of Intelligent Design, it ain’t here.

The only useful information I got out of the book was a realization of just how profoundly peculiar Behe’s ideas about evolution actually are. I’ve read some of his past interviews, and he always goes out of his way to explain that he has no problem with common descent, and that he does believe we can trace our ancestry back to other organisms. I’d gotten the impression that he was some kind of theistic evolutionist, who believes in the general process of evolution, but thinks some kind of designer had to intervene at discrete points in history to shape life in a particular direction. Call me naive, call me confused, but I had no idea how strange Behe’s ideas about evolution actually are.

Behe thinks evolution can manage relatively minor tweaks to an organism; it can refine physiological performance, for instance, and can generate the kinds of variation we see within extant populations. But it is powerless to generate the kinds of change that produce new species or genera (the scope of allowed natural change is unclear). We are all little isolated islands of variation within a sharply delimited range.

But we are all still related by common descent, a term that does not mean in Behe’s hands the same thing that it means to non-creationist scientists. How does that work? The Designer has to explicitly and specifically modify a species to generate a new form. So Homo was sculpted from our last common ancestor with Pan by the conscious intent of an intelligent agent. Actually, every spe… no, it’s not clear what taxonomic unit is the limit, so let’s call them “kinds”…every “kind” had to be conjured into existence by the Designer. I think we can rule out the oft-mentioned idea that he could be talking about intelligent space aliens working as the designers, now—this is a model in which every kind of organism on the planet over its entire history had to be artificially created from its predecessors.

Where is the “edge of evolution”? He has a little diagram to illustrate it.

i-8ab347c1f1ba2648e68e990222758c51-edge_of_evo.gif

Everything in solid black is the product of design. Everything in white, that is everything from variation within species to individual mutations, he’s willing to concede to accidental or non-intentional causes. The gray area above species is the edge, where he’s not precisely certain the line should be drawn. That Designer sure has been busy! He’s been working hard to sculpt life on earth towards generating human beings and chimpanzees and malaria parasites, right down to specifying the amino acid sequences of active sites in their proteins. Cells, genes, regulatory networks, all that fundamental stuff is the direct handiwork of a mysterious designer which Behe will leave nameless and unexplored.

As I’ve already mentioned, he’s not going to offer any descriptions or evidence for this amazingly persistent and industrious Designer, so the entire argument is going to rest on his assertion of barriers to variation that cannot be overcome without intelligent aid. Wouldn’t you know it, though—there’s nothing new in his argument, and he mainly just reworks bad old creationist claims about probability.

The centerpiece of his argument in this book is malaria, just as the flagellum was his big evolution-killer in Darwin’s Black Box, and he’s going to make all kinds of sweeping conclusions from a misleading derivation of probabilities in this one organism.

He invents a new metric, the CCC, or “chloroquine complexity cluster”. This is the probability of evolving a fairly simple trait in the malaria parasite, resistance to a compound called chloroquine. Malaria that is resistant to chloroquine has two specific changes to a protein pump called PfCRT; one amino acid at position 76 and another at position 220 are changed from the more common form. By a couple of arguments, from the probability of getting two independent changes in the sequence and the observed frequency of evolution of chloroquinone resistance in the population of infected people, he comes up with a number: the odds of acquiring this specific pair of mutations is one in 1020. Fair enough; if you demand a very specific pair of amino acid changes in specific places in a specific protein, I agree, the odds are going to be very long on theoretical considerations alone, and the empirical evidence supports the claim of improbability for that specific combination.

But now Behe pulls a classic creationist switcheroo. He has one number, a very tiny probability of one in 1020 for one specific result, and he’s going to use this magic CCC value to claim that no significant evolution can have occurred in humans in ten million years of evolution. Not ‘it’s highly unlikely that humans would have acquired this predetermined pair of amino acid changes in a particular protein,’ but ‘no useful pair of amino acid changes anywhere in any of their gene products.’ No, you’re thinking: he couldn’t possibly have said something that stupid. But yes, he really did.

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.

Wait…so complexity is the same as improbability? He goes even further; he argues that no CCC equivalent arose in the entire order of mammals over the entire span of their existence.

Mammals are thought to have arisen reptiles and then diversified into a spectacular array of creatures, including bats, whales, kangaroos, and elephants. Yet that entire process would—if it occurred through Darwinian mechanisms—be expected to occur without benefit of a single mutation of the complexity of a CCC. Strict Darwinism requires a person to believe that mammalian evolution could occur without any mutation of the complexity of this one.

Whoa.

Behe is basically arguing for the special creation of each and every mammalian form; that although the designer worked by modifying existing stocks, he/she/it had to go in and specifically add in every unique, complex attribute that distinguishes one from another, right down to different levels of resistance to species-specific pathogens. Behe isn’t just a crackpot who thinks he has a novel explanation for an evolutionary mechanism—he’s a radical anti-evolutionist extremist who rejects the entire notion of the transformation of species by natural processes.

Yet his argument for this dramatic conclusion is not only weak, it’s wrong. I could, for instance, correctly argue that the odds of getting a straight flush dealt to you in a 5 card poker hand is about 1 in 6×104; we could calculate this with probability theory, and we could also deal lots of poker hands and determine it empirically. No one’s going to argue with that part of the math.

But now, if I were to define a Straight Flush Complexity Cluster (SFCC) parameter and wave it around and claim that “no hand of the same complexity as a straight flush has been dealt by chance in the last ten years of poker games here in town,” that players can only possibly win one hand in 60,000, or worse, that no one has won a poker hand without cheating and stacking the deck, you’d know I was crazy. But that is basically Behe’s entire argument — he claims to have found the “edge of evolution,” and that it is much sharper and steeper and more impassable than anyone but a creationist could believe.

One more problem: he’s dimly aware that there might be some weakness in his argument along the lines of what I just explained, and he dedicates one whole paragraph to trying to plug the hole. He argues that many mutations occur in the malaria genome, and that there is so much churn that “mutations in all of the amino acid positions of all of the proteins of malaria” can be expected to occur by chance, yet only these two particular changes have been so far found to confer chloroquine resistance. It’s an admission that the target for this particular solution is very, very narrow within the search space of the genome of the extant malaria parasite. That’s fine, I can see that, but it doesn’t address the problem with his generalization: it does not mean that the range of solutions to all problems in evolution are similarly so tightly constrained, yet he is pretending that they are. He doesn’t understand that I don’t need to get a straight flush to win every poker game; sometimes a pair will do. He also doesn’t seem to understand that, just as in many poker games I can discard and draw, so too in evolution we can take an incremental approach: a single mutation that helps a little bit may be retained and promote the fitness of a lineage until a second mutation can improve it yet more.

That’s just the third chapter, where Behe argues for “the mathematical limits of Darwinism” on specious grounds. The whole book has this same problem of tired old creationist arguments spruced up with pseudoscholarly language. Mark Chu-Carroll has really shredded this part of the book, and also deals with the amazingly incompetent mish-mash he has made of the concept of adaptive landscapes; ERV has run with that and shown that Behe’s idea of how landscapes work is a cartoon version of reality. Nick Matzke has an interesting discovery: Behe also continues to tout the cilium as an example of irreducible complexity, but Nick discovers a prime example of reduced complexity of the cilium…in the malaria parasite. This book keeps pounding away at that plasmodium, you’d think he’d have noticed.

I think you can expect many more such dissections that expose the rank incompetence of this book. Most of the arguments are gussied up versions of the kind of handwaving, ignorant rationalizations you’d get from some pomaded fundagelical Baptist minister who got all his biology from the Bible, not at all what you’d expect from a tenured professor of biochemistry at a good university—throwing in an occasional technical gloss or mangled anecdote from the literature is only a gloss to fool the rubes.

This has only been a too-long dismissal of one of the early, obviously fallacious points in the book. And because it’s too long, I’m going to stop here for now—next, I want to jump ahead and focus on one chapter. Chapter 9. “The Cathedral and the Spandrels.” In that chapter, Behe tries and fails to dismiss all of development and evo-devo of having any significance in understanding evolution, and goes after Sean Carroll and Eric Davidson. Trust me, he does an even worse job of that than he does in trying to dismiss all of evolution on the basis of the probability of two amino acid changes.


Several people have pointed out that his calculation of the frequency of evolution of cloroquine resistance seems dubious. Here’s his rationale.

The mutant PfCRTs exhibit a rang of changes, affecting as few as four amino acids to as many as eight. However, the same two amino acid changes are almost always present—one switch at position number 76 and another at position 220.

Since two particular amino acid changes occur in almost all of these cases, they both seem to be required for the primary activity by which the protein confers resistance.

… [several pages later]

…resistance to chloroquine has appeared fewer than ten times in the whole world in the past half century. Nicholas White of Mahidol University in Thailand points out that if you multiply the number of parasites in a person who is very ill with malaria times the number of people who get malaria per year times the number of years since the introduction of chloroquine, then you can estimate that the odds of a parasite developing resistance is roughly one in a hundred billion billion.

That’s it. That’s the entire rationale. It’s very poor, and even granting it to him, it’s still not applicable to the whole problem of evolution.

Comments

  1. #1 Blake Stacey, OM
    June 5, 2007
  2. #2 Blake Stacey, OM
    June 5, 2007

    Yeesh. I’m impressed he managed to squeeze so much falsehood and misrepresentation into a single diagram.

    I’m also getting pretty tired of the fine-tuning two-step. First, you say that the laws of nature are cunningly devised so that life may arise, and then you say that it’s impossible for life to do anything. Which is it: a hospitable universe or an inhospitable one? And if the history of life is so improbable that it could never have happened naturally, why don’t we see physical laws and constants of nature so hostile to life-as-we-know-it that such life as ourselves could never arise? Conversely, if the fundamental principles of physics and cosmology were so well chosen that life of our kind was possible, or even perhaps inevitable, why couldn’t the mechanisms of genetics perform equally well?

    The whole argument is incoherent; its only saving grace is that it is also wrong. As Sean Carroll once wrote,

    But in fact there is a better reason to be skeptical of the fine-tuning claim: the indisputable fact that there are many features of the laws of nature which don’t seem delicately adjusted at all, but seem completely irrelevant to the existence of life. In a cosmological context, the most obvious example is the sheer vastness of the universe; it would hardly seem necessary to make so many galaxies just so that life could arise on a single planet around a single star. But to me a more pointed observation is the existence of ”generations” of elementary particles. All of the ordinary matter in the universe seems to be made out of two types of quarks (up and down) and two types of leptons (electrons and electron neutrinos), as well as the various force-carrying particles. But this pattern of quarks and leptons is repeated threefold: the up and down quarks are joined by four more types, just as the electron and its neutrino are joined by two electron-type particles and two more neutrinos. As far as life is concerned, these particles are completely superfluous. All of the processes we observe in the everyday workings of the universe would go on in essentially the same way if those particles didn’t exist. Why do the constituents of nature exhibit this pointless duplication, if the laws of nature were constructed with life in mind?

  3. #3 Brownian
    June 5, 2007

    Actually, every spe… no, it’s not clear what taxonomic unit is the limit, so let’s call them “kinds”…every “kind” had to be conjured into existence by the Designer.

    So how improbable is the mutation that causes my eyes to bleed everytime I read the word ‘kinds’ in a creationist context?

  4. #4 Blake Stacey, OM
    June 5, 2007

    gg:

    Heh heh heh. Who was that mysterious masked meddler who quoted Carl Sagan —

    There is something stunningly narrow about how the Anthropic Principle is phrased. Yes, only certain laws and constants of nature are consistent with our kind of life. But essentially the same laws and constants are required to make a rock. So why not talk about a Universe designed so rocks could one day come to be, and strong and weak Lithic Principles? If stones could philosophize, I imagine Lithic Principles would be at the intellectual frontiers.

    And then said,

    If we go by what is actually most prevalent in the Universe, it seems that the Cosmos was made for the benefit of dark energy, with matter merely an incidental elaboration.

    At some point, I should write up the history of dark energy and suchlike. It’s an interesting development, and sadly, the popularizations of cosmology from before 1998 are out of date.

  5. #5 Sastra
    June 5, 2007

    Uh-oh — that chart Behe made, where he explicitly shows what comes out of accidental or unintentional causes, lists “individuals.” God did not specifically have anything to do with planning individuals. He doesn’t intervene on that level.

    Does that mean that we were not created lovingly by God for a purpose? We’re all just cosmic accidents, because all He cares about is the “kind?” Moms and dads just happen to meet, we just happen to be born.

    Behe is taking away Meaning. Meanie.
    Heretic.

  6. #6 Blake Stacey, OM
    June 5, 2007

    gg:

    Did you hear about the dark matter “smoke ring”?

  7. #7 Torbj÷rn Larsson, OM
    June 5, 2007

    now Behe pulls a classic creationist switcheroo

    A classic Modesty Blaise-Willie Garwin tactic in a tight spot is the “high-low switcheroo”. (One reverses high and one reverses low to surprise surrounding attackers.)

    But this is a low-brow switcheroo. And don’t get me started on how it places Behe in a tight spot.

    some pomaded fundagelical Baptist minister

    But Behe is a slick flaggelical Creationist minister; I’m not sure I would expect much of a difference.

    Why do the constituents of nature exhibit this pointless duplication, if the laws of nature were constructed with life in mind?

    Yes, or to paraphrase Kronecker, evolution created 10 fingers, all remaining numbers is the work of man.

    Actually, I think the possibility of the landscape drives some of the more educated creationists crazy. The string landscape may have 10^500 different solutions, which is a bit more constrained than the infinity of possible vacua of field theories, but it is still way more nature given possibility than they like.

  8. #8 David Marjanovi?
    June 5, 2007

    The black bar in the diagram is the Gap, the one where the God of the Gaps lurks. The gray bar is where the Gap has been shrinking. The white bar is where the Gap has already retreated from.

    Oh, and, PZ, are you a closet entomologist? I’d love to see a classification that contained “the entire order of mammals”! Would be a nice change. :o)

  9. #9 David Marjanovi?
    June 5, 2007

    The black bar in the diagram is the Gap, the one where the God of the Gaps lurks. The gray bar is where the Gap has been shrinking. The white bar is where the Gap has already retreated from.

    Oh, and, PZ, are you a closet entomologist? I’d love to see a classification that contained “the entire order of mammals”! Would be a nice change. :o)

  10. #10 Blake Stacey, OM
    June 5, 2007

    Torbj÷rn Larsson, OM:

    And somewhere else in that landscape is a D2-brane populated by Flatlanders, whose pentagram-shaped scientists are trying vainly to convince the smug, self-satisfied circles of the priesthood that universes of three dimensions could contain intelligent life.

  11. #11 Blake Stacey, OM
    June 5, 2007

    ERV:

    Maybe I have a twisted view of things, with HIV, but impossible mutations happen every day, in every HIV patient. Every day.

    Could we perhaps say, “HIV experiences six impossible mutations before breakfast”?

  12. #12 AndrÚs Diplotti
    June 5, 2007

    He insisted that he accepted common descent, though, and acknowledged all this evidence that, for instance, chimpanzees and humans are related by common descent, while saying that it was impossible for them to have evolved naturally from one to the other.

    Wait a minute… So he’s saying that humans do come from apes? Isn’t this the same ridiculous, untenable, awful, godless claim creationists oppose? How come they’re championing Behe?

  13. #13 Blake Stacey, OM
    June 5, 2007

    I think I found the article Behe cites in that last quoted passage — Nicholas J. White’s “Antimalarial drug resistanceJ. Clin. Invest. 113:1084-1092 (2004). It’s available for free online.

    The genetic events that confer antimalarial drug resistance (while retaining parasite viability) are spontaneous and rare and are thought to be independent of the drug used. They are mutations in or changes in the copy number of genes encoding or relating to the drug’s parasite target or influx/efflux pumps that affect intraparasitic concentrations of the drug (Table 1). A single genetic event may be all that is required, or multiple unlinked events may be necessary (epistasis). As the probability of multigenic resistance arising is the product of the individual component probabilities, this is a significantly rarer event. P. falciparum parasites from Southeast Asia have been shown to have an increased propensity to develop drug resistance (12).

    Chloroquine resistance in P. falciparum may be multigenic and is initially conferred by mutations in a gene encoding a transporter (PfCRT) (13). In the presence of PfCRT mutations, mutations in a second transporter (PfMDR1) modulate the level of resistance in vitro, but the role of PfMDR1 mutations in determining the therapeutic response following chloroquine treatment remains unclear (13). At least one other as-yet unidentified gene is thought to be involved. Resistance to chloroquine in P. falciparum has arisen spontaneously less than ten times in the past fifty years (14). This suggests that the per-parasite probability of developing resistance de novo is on the order of 1 in 10^20 parasite multiplications. The single point mutations in the gene encoding cytochrome b (cytB), which confer atovaquone resistance, or in the gene encoding dihydrofolate reductase (dhfr), which confer pyrimethamine resistance, have a per-parasite probability of arising de novo of approximately 1 in 10^12 parasite multiplications (5). To put this in context, an adult with approximately 2% parasitemia has 10^12 parasites in his or her body. But in the laboratory, much higher mutation rates than 1 in every 10^12 are recorded (12).

  14. #14 Blake Stacey, OM
    June 5, 2007

    Oops. I hit “Post” too soon. The following paragraph of White’s article suggests that (a) mutant P. falciparum with chloroquine resistance are less fit than their non-mutated cousins in the absence of chloroquine, or (b) the host’s immune responses eliminate mutants we would otherwise see, making the in vivo rate much lower than the in vitro.

    (If I can parse the jargon correctly, that is.)

  15. #15 Blake Stacey, OM
    June 5, 2007

    Merci mille fois, M. Matzke!
    :-)

    The point about “consider the filters” had occurred to me, too, although I’m far from a professional in this field. Just before I saw your comment here, I mentioned it at Aetiology, so you might want to post your comment there, too.

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