Transcript: American Museum of Natural History
April 23, 2002
(Part Six: Dr. Michael Behe)
Dr. Michael Behe is a professor of biochemistry at Lehigh University. He holds a PhD. in biochemistry from the University of Pennsylvania. He has done post-doctoral work on DNA structure at the National Institutes of Health, and formerly was assistant professor of chemistry at Queen's College in New York City. Local color here. He didn't write that part, I just put that in there. He has authored over forty technical papers and one book, Darwin's Black Box: The Biochemical Challenge to Evolution, which argues that living systems at the molecular level are best explained as being the result of deliberate Intelligent Design. Darwin's Black Box has been reviewed by the New York Times, Nature, Philosophy of Science, Christianity Today, and over one hundred other periodicals. He and his wife reside near Bethlehem, Pennsylvania with their eight children, Mike, would you, uh, like to begin? [Applause]
I'm a short guy. Um, Thanks very much Genie. As Genie mentioned, uh, um, I taught at Queen's college, and City University in the early eighties, it's really nice to be back in New York City. My wife grew up on [cambrilling Ave?] in the Bronx near 187th street, and our first daughter, Grace was born here, so New York has a lot of happy memories for the Behe family. My talk will be divided into four parts, I believe. Uh, well let me continue while somebody tries to, to fix things up here. Thanks Ken. First I'll talk a, give a sketch of the argument for design, second I'll talk about some common misconceptions about what I call the mode of design, third, misconceptions about biochemical design, and finally a discussion of the future prospects of design. Before I begin, however, I'd like to emphasize that the focus of my argument will not be descent with modification, with which I agree. Rather, the focus will be the mechanism of evolution. How did all this happen, by natural selection or intelligent design, my conclusion will not be that natural selection doesn't explain anything, rather the conclusion will be that natural selection doesn't explain everything. So, let's begin with a sketch of the Design argument.
In the Origin of Species, Darwin emphasized that his was a very gradual theory. Natural selection had to work by numerous, successive, slight modifications to pre-existing theori-, er, pre-existing structures, however, irreducibly complex systems seem quite difficult to explain in gradual terms. What is irreducible complexity? I've defined the term in various places, but it's easier to illustrate what I mean with the following example, the mousetrap. [Laughter] Close your eyes, and imagine it. [cheers]…alright, okay, thank you very much. I'm going to have to zing ahead here a little bit. Uh, this is a slow one. I'm going to have wait, I pressed it a couple times so I'm going to have to wait until it catches up with my pressing. [pause] So, this mousetrap here…mousetraps [clears throat]. Um, the common mousetrap, the common mechanical mousetrap has a number of interacting parts that all contribute to its function, and if any parts are taken away, the mousetrap doesn't work half as well as it used to, or a quarter as well as it used to, the mousetrap is broken. Thus it is irreducibly complex. Suppose we wanted to evolve a mouse trap as something like a Darwinian process. What would we start with? Would we start with a wooden platform and hope to catch mice inefficiently, perhaps tripping them [ laughter]. And then add say the holding bar, hoping to improve the efficiency. No, of course we can't do that, because irreducibly complex systems only acquire their function when the system is essentially completed. Thus, irreducibly complex systems are real headaches for natural selection, because it is very difficult to invision how they could be put together, that is put together without the help of a directing intelligence, by the numerous successive, slight modifications that Darwin insisted upon. Irreducibly complex biological systems would thus be real challenges to Darwinian evolution. Yet modern science has discovered irreducibly complex systems in the cell. An excellent example is the bacterial flagellum, which is literally an outboard motor that bacteria use to swim. The flagellum has a large number of parts that are necessary for its function, a propeller, hook, drive shaft and more. Thorough studies show it requires 30-40 protein parts, and in the absence of virtually any of those parts, the flagellum doesn't work, or doesn't even get built in the cell. It's gradual evolution by unguided natural selection, therefore, is a real headache for Darwinian theory. I like to show audiences this picture of the flagellum, because when they see it, they quickly grasp that this is a machine. It is a real molecular machine, it is not just like a machine, it is a real machine and perhaps that will help us think about its origin. I have written that, not only is the flagellum a problem for Darwinism, but that it is better explained as the result of design, deliberate design by an intelligent agent. Some of my critics have said that design is a religious conclusion. But I disagree. I think it is wholly empirical, that is, the conclusion of design is based on the physical evidence, along with an appreciation for how we come to a conclusion of design. Now Bill does it with statistics, I do it with a, a much more intuitive approach. Uh, to illustrate how we can come to a conclusion of design, let's look at the following. This is a Farside cartoon by Gary Larson showing a troop of jungle explorers, and the lead explorer has been strung up and skewered, and this fellow turns to him and says, that's why I never walk in front. Words to live by. Let me tell you. [laughter]. Now everyone in this room looks at this cartoon and you immediately realize that this trap was designed. It was not an accident. The humor of the cartoon depends on you recognizing the design. But how do you know that? How do you know the trap was designed? Is it a religious conclusion? Probably not. [laughter] You know it's designed because you see a number of very specific parts, interacting to produce a function that the parts themselves could not produce. You see something like irreducible complexity, or specified complexity. Now I will address the common misconceptions about what I call the mode of design, that is, how design may have happened.
My Book, Darwin's Black Box, in which I flesh out, uh, these ideas, has been pretty widely discussed in a number of publications. What have other scientists said about it? Well they've said many things, not all of them flattering. Uh... But the general reaction is well summarized in a recent book called the Way of the Cell, published last year by Oxford University Press, and authored by Colorado State University biochemist Franklin Harold. And he writes, "We should reject as a matter of principle the substitution of Intelligent Design for the dialogue of chance and necessity", and he cites my book. "But we must concede, that there are presently no detailed Darwinian accounts of the evolution of any biochemical system, only a variety of wishful speculations." Now let me take a moment to emphasize Harold's two points. First, he acknowledges that Darwinists have no real explanations for the enormous complexity of the cell, only hand waving speculations, more colloquially know as "just so stories". "How the Rhinoceros got its horn". "How the bacterium got its flagellum" [laughter]. I find this an astonishing admission for a theory that has dominated biology for so long. Second, apparently he thinks that there is some principle that forbids us from investigating the idea of Intelligent Design, even though Design is an obvious idea that quickly pops into your mind when you see a drawing of the flagellum or other complex biochemical systems. But what principle is that? I think the principle boils down to this. [pause-laughter] Design appears to point strongly beyond nature. It has philosophical and theological implications, and that makes many people uncomfortable. But any theory that purports to explain how life occurred will have philosophical and theological implications. For example, the Oxford biologist Richard Dawkins has famously said that "Darwin made it possible to be an intellectually fulfilled atheist". Disagreeing with him, Ken Miller wrote in his book that God used evolution as the tool to set us free. Stuart Kauffman, a leading complexity theorist who disagrees with Darwinism, here is the quote "Darwinism is not enough. Natural selection cannot be the sole source of order in the world." He thinks that his ideas have philosophical consequences and that would show us that we are at home in the universe. So all theories of origins carry philosophical and theological implications. But how could biochemical systems have been designed? Did they have to be created from scratch in a puff of smoke? No. The Design process may have been much more subtle. It may have involved no contravening of natural laws at all. Let's consider just one possibility, and I'm gonna borrow from Ken again. Suppose the designer is God, as most people would suspect. Well, that as Ken has pointed out in his book, Finding Darwin's God, a subtle God could cause mutations by influencing quantum events such as radioactive decay. Something that I would call guided evolution. Now I don't think Ken thinks of guided evolution, but that, uh, that could have occurred, and I agree with Ken on this. It seems perfectly possible to me. I would only add that the process would amount to Dar-, eh, to Intelligent Design, not Darwinian evolution. Now let's talk, eh, talk about common misperceptions about biochemical design.
Some Darwinists have proposed that a way around the problem of irreducible complexity could be found if the individual components of a system first had other functions in the cell. For example, consider a hypothetical example such as pictured here, where all of the parts are supposed to be necessary for the function of the system. Might the system have been put together from individual components that originally worked on their own, but then got together. Unfortunately this picture greatly oversimplifies the difficulty as I discussed in Darwin's Black Box. Here analogies to mousetraps break down somewhat, because the parts of the system have to automatically find each other in the cell. They aren't arranged by an intelligent agent as a mousetrap is. To find each other in the cell, interacting parts have to have their surfaces shaped so that they are very closely matched to each other. Originally, however, the individually acting components would not have had complementary surfaces. So all of the interacting surfaces, of all of the components, would first have to be adjusted, before they could function together, and only then would the new function of the composite system appear. Thus the problem of irreducibility remains, even if individual components separately had their own functions. Another area where one has to be careful is in noticing that some systems with extra or redundant components may have an irreducibly complex core. For example, a care with four spark plugs might get by with three or two. But it certainly can't get by with none. Rattraps often have two springs to give them extra strength, they can still work if one spring is removed, but they can't work with both springs are removed. Thus in trying to imagine the origin of a rattrap by Darwinian means, we still have all the problems we had with a mousetrap. A cellular example of redundancy is the hugely complex eukaryotic cilium, shown here in cross section, which has multiple copies of a number of components, yet needs at least one copy of each to work, as I pictured in my book. Many other criticisms have been made against Intelligent Design, and I have responded to a number of them at the following locations. I will now discuss how I view the future prospects of the theory of Intelligent Design.
I see them as very bright indeed. Why? Because the idea of Intelligent Design has advanced not primarily because of anything I or any individual has done. Rather, it's been the very progress of science itself that has made Intelligent Design plausible. Fifty years ago, much less was known about the cell and it was much easier then to think that Darwinian evolution was true. But with the discovery of more and more complexity at the foundation of life, the idea of intelligent design has gained strength. That trend is continuing. As science pushes on, the complexity of the cell is not getting any less. On the contrary, it is getting much greater. For example, a recent issue of the journal Nature carried the most detailed analysis yet of the total protein complement of yeast, the so-called yeast "proteome". The authors point out that most proteins they investigated in the cell function as multi-protein complexes, not as solitary proteins as scientists had long thought. In fact, they showed that almost 50% of the proteins in the cell function as complexes of a half dozen or more, such as the polyadenelation machinery shown in this figure from the paper. To me, this implies that irreducible molecular machinery is very likely going to be the rule in the cell, not the exception. We will probably not have to wait too long to see. Another example comes from a paper published in the Journal of Molecular Biology two years ago, which showed that some enzymes have only a limited ability to undergo multiple changes in their amino acid sequence, even when the enzymes function alone, as single proteins, and even when the changes are very conservative ones. This lead the author to caution that, quote, "homologues sharing less than about two-thirds sequence identity should probably be deemed as distinctive designs with their own optimizing features." The author pictured such proteins as near islands of function, virtually isolated from neighboring protein sequences. This may mean that even individual proteins, uh, from separate species that are similar but not identical in their amino acid sequence, might not have been produced by a Darwinian process, as most scientists thought, and as even I was willing to concede. Perhaps even I give too much unearned credit to Darwinian theory. Finally, to show what specific research questions might be asked by a theory of Intelligent Design, I'd like to briefly describe a little bit of my own work. This is title slide of a seminar I gave six-weeks ago to the biotechnology group at Sandia National Laboratory. The title, "Modeling the Evolution of Protein Binding Sites: Probing the, the dividing line between Natural Selection and Intelligent Design", points to a question I'm very interested in exploring. If you are someone like myself who thinks that some things in biology are indeed purposely designed, but that not all things are designed, then a question, which quickly arises, is, "Where is the broad dividing line between Design and unintelligent processes?" I think that question has to be answered at the molecular level, specifically in terms of protein structure. Drawings of the bacterial flagellum picture proteins as bland spheres or ovals, but each protein in the cell is actually itself very complex. This ribbon drawing of bovine pancreatic trip?? inhibitor gives a little taste of that complexity. Now proteins are polymers of amino acid residues and some structural features of proteins require the participation of multiple residues. For example, up here, I know it's hard to see, but this yellow link is called a disulfide bond. A disulfide bond requires two cystaine?? residues. Just one ?? residue can't form such a bond. Thus in order for a protein that did not have a disulfide bond to evolve one, several changes in the same gene have to occur. Thus in a sense, the disulfide bond is irreducibly complex, although not really to the same degree of complexity as systems made of multiple proteins. The problem of irreducibility, irreducibility in proteins is a general one. Whenever a protein interacts with another molecule as all proteins do, it does so through a binding site whose shape and chemical properties closely match the other molecule. Binding sites however, are composed of perhaps a dozen amino acid residues, and binding is generally lost if any of the positions are changed. One can then ask the question, how long would it take for two proteins that originally interact to evolve the ability to bind each other by random mutation and natural selection, if binding only occurs when all positions have the correct residue in place. Although it would be difficult to experimentally investigate the question, the process can be simulated on a computer. Here is just a sample of the data I have generated over the past year or so, the filled circles are data points from a number of simulations, which were all fit, uh, by the following equation, the details of which I will not bother you with, with here. These results were presented last summer in Philadelphia at the meeting of the Protein Society. In the next slide, the log of the expected time to generate what I call irreducible complex, irreducibly complex protein features, is shown as the function of the log of the population size and the log of the probability of the feature. The yellow dot is the time expected to generate a new disulfide bond in a protein that did not have one if the population size is 100,000,000 organisms. The expected time is roughly a million generations. The red dot shows that the expected time needed to generate a new protein binding site would be 100 million generations. Using data from these simulations, as well as Bill Dembski's concept of probabilistic resources, we can come to several broad, tentative conclusions. First, that undirected, irreducibly complex mutations cannot have been regularly involved in the evolution of large animals; the time frame would just be too long. And second, that undirected, irreducibly complex systems of the complexity of two or more protein binding sites, cannot have been regularly involved in the evolution of vertebrates, for the same reason. This work assumed that all mutations were neutral. Future work could investigate such questions as, "what if intermediate mutations are selected against?" and "what happens if there is competition between irreducibly complex mutations and single site mutations." The broad motivation behind this work is to start getting some good numbers to plug into Bill Dembski's explanatory filter. To try to come to a reasoned conclusion about where in nature design leaves off. In summary, I want to leave you with four take home points. First, that the question is open; no other scientific theory has yet explained the data. Second, that intelligent design is an empirical hypothesis that flows easily from the data, as you can tell by looking at a drawing of the flagellum. Third, that there is no principle that forbids our considering design. And best of all, fourth, that there are exciting research questions that can be asked within a design framework. Thanks very much. [Applause]
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October 31, 2002