Why Darwin Matters Page 8
But the Explanatory Filter assumes probabilities that cannot be determined in practice; it is nothing more than a thought experiment and cannot practically be used in science. Indeed, in order to eliminate all necessity and chance explanations assumes that we know all configurations of these explanations, which, of course, we do not. Even if we did, and rejected them all, the design inference does not follow. Design, as it is commonly defined by the Intelligent Design movement, means purposeful and intelligent creation, not simply the elimination of necessity and chance. In other words, design is not just a default conclusion when all else fails to explain. Design requires positive evidence, not the rejection of negative evidence. The Explanatory Filter cannot survive the scrutiny of two skeptical principles—the Burden of Proof and the Either-Or Fallacy.
In addition, even if positive evidence for design were presented, by the logic of the Explanatory Filter we should be able to apply the filter to the design’s designer. Assuming necessity and chance are mathematically (if not morally) rejected for the design’s designer, the logical conclusion would be that the design’s designer was designed, and that that design’s designer’s designer was also designed, ad infinitum. If the Explanatory Filter’s design does not explain Intelligent Design, then by the logic of the Explanatory Filter we have to infer that necessity or chance created the Intelligent Designer. By the logic of Shermer’s Last Law, as we saw in the preceding chapter, the Explanatory Filter asserts that the Intelligent Designer and Extra-Terrestrial Intelligence are indistinguishable.
The ultimate answer to the design inference is to provide a cogent theory of natural design that can account for the complexity of the universe and life. This we have through the sciences of complexity, in which we recognize the properties of self-organization and emergence that arise out of complex adaptive systems. Self-organization means that the system requires only an input of energy into it in order to generate an action, which comes from within the system itself. An emergent property is one that is more than the sum of its parts. Complex adaptive systems are those that grow and learn as they change, and they are autocatalytic, which means that they contain self-driving feedback loops. For example:
Water is a self-organized emergent property of a particular arrangement of hydrogen and oxygen molecules.
Consciousness is a self-organized emergent property of billions of neurons firing in patterns in the brain.
Language is a self-organized emergent property of thousands of words spoken in communication between language users.
Law is a self-organized emergent property of thousands of informal mores and restrictions that were codified over time into formal rules and regulations as societies grew in size and complexity.
Economy is a self-organized emergent property of millions of people pursuing their own self-interests without any awareness of the larger system in which they work.
Life is a self-organized emergent property of prebiotic chemicals; complex life is a self-organized emergent property of simple life, where simple prokaryote cells self-organized to become more complex eukaryote cells (many of the little organelles inside cells were once self-contained independent cells); multicellular life is a self-organized emergent property of single-celled life; and so on up the chain of complexity to colonies, social units, societies, consciousness, language, law, and economies.
Self-organization is itself an emergent property, and emergence is a form of self-organization. The system is self-repeating, and therefore there is no need to invoke an Intelligent Designer.
The design inference comes naturally. The reason people think that a Designer created the world is because it looks designed. I think we should quit tiptoeing around this inference and admit that life looks designed because it was: from the bottom up, by evolution. The reason design appears artifactual to us is because evolutionary design is based on functional adaptation. Form follows function, function follows design, and natural selection selects among those designs that are most functional; that is, they enable the organism to survive and reproduce. When we use words like “design,” “form,” and “function,” it sounds purposeful because we are accustomed to using these terms to describe human action, which we equate with purpose and intelligence. But in fact, the science of complexity shows how design, form, and function are all derivatives of self-organized emergent complex systems.
Irreducible Complexity: Evolution cannot account for the stepwise gradual increase in complex systems.
In the Origin of Species Darwin wrote: “If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down.”24 Creationists have been in search of Darwin’s exception ever since. Lehigh University biochemist Michael Behe thinks he has found several examples of living properties that he says are “irreducibly complex”:
By irreducibly complex I mean a single system composed of several well-matched, interacting parts that contribute to the basic function, wherein the removal of any one of the parts causes the system to effectively cease functioning. An irreducibly complex system cannot be produced directly (that is, by continuously improving the initial function, which continues to work by the same mechanism) by slight, successive modifications of a precursor system, because any precursor to an irreducibly complex system that is missing a part is by definition nonfunctional. Since natural selection can only choose systems that are already working, then if a biological system cannot be produced gradually it would have to arise as an integrated unit, in one fell swoop, for natural selection to have anything to act on.25
The human eye is a favorite example among Intelligent Design creationists because of its irreducible complexity—take out any one part and it will not work. How could natural selection have created the human eye when none of the individual parts themselves have any adaptive significance? Or consider the bacteria flagellum, Behe’s type specimen of irreducible complexity and intelligent design—the little tail that propels the cell is complex and composed of many parts, and the removal of any one of them would cause the system to cease working. The bacteria flagellum is not like a machine, it is a machine, and it has no antecedents in nature from which it could have evolved in a stepwise Darwinian manner.
Irreducible complexity leads to an inference of intelligent design, an inference that Behe immodestly claims “is so unambiguous and so significant that it must be ranked as one of the greatest achievements in the history of science.” He equates it with the discoveries of “Newton and Einstein, Lavoisier and Schrodinger, Pasteur, and”—with gumption—“Darwin.”26 There is even an emotional appeal to the struggle of Intelligent Design theorists for recognition of their scientific searches beyond the facile attribution of design to Darwin. “It is a shock to us in the twentieth century to discover, from observations science has made, that the fundamental mechanisms of life cannot be ascribed to natural selection, and therefore were designed. But we must deal with our shock as best we can and go on,” Behe pleads. “The theory of undirected evolution is dead, but the work of science continues.”27
Yes, the work of science does continue, and scientists in Behe’s field of biochemistry and microbiology have responded to his claims.
First, when Behe says that “any precursor to an irreducibly complex system that is missing a part is by definition nonfunctional,” he is committing the fallacy of bait-and-switch logic, says the philosopher of science Robert Pennock. He is reasoning from something that is true “by definition” to something that is proved through empirical evidence. Every time someone finds an example in nature that is simpler than Behe said it could be, Behe redefines irreducible complexity to that simpler level of complexity.28 In other words, irreducible complexity is what Behe says it is, depending on the example at hand.
Second, the evolutionary biologist Jerry Coyne, responding to Behe directly, identified a number of biochemical pathways that Behe has claimed are impossible to explain without
an Intelligent Designer but which, in fact, “have been rigged up with pieces co-opted from other pathways, duplicated genes, and early multi-functional enzymes.” Behe, for example, claims that the blood clotting process could not have come about through gradual evolution. Coyne shows that in fact thrombin “is one of the key proteins in blood clotting, but also acts in cell division, and is related to the digestive enzyme trypsin.”29 In other words, thrombin evolved for one purpose and was later coopted for other purposes.
Third, Behe’s irreducible complexity is a more sophisticated version of an argument made against Darwin in the nineteenth century known as the problem of incipient stages. Fully formed wings are obviously an excellent adaptation for flight that provide all sorts of advantages for animals who have them; but of what use is half a wing? For Darwinian gradualism to work, each successive stage of wing development would need to be functional, but stumpy little partial wings are not aerodynamically capable of flight. Darwin answered his critics thus:
Although an organ may not have been originally formed for some special purpose, if it now serves for this end we are justified in saying that it is specially contrived for it. On the same principle, if a man were to make a machine for some special purpose, but were to use old wheels, springs, and pulleys, only slightly altered, the whole machine, with all its parts, might be said to be specially contrived for that purpose. Thus throughout nature almost every part of each living being has probably served, in a slightly modified condition, for diverse purposes, and has acted in the living machinery of many ancient and distinct specific forms.30
This solution is called exaptation, in which a feature that originally evolved for one purpose is coopted for a different purpose.31 The incipient stages in wing evolution had uses other than for aerodynamic flight—half wings were not poorly developed wings, they were well-developed something elses—perhaps thermoregulating devices. The first feathers in the fossil record, for example, are hairlike and resemble the insulating down of modern bird chicks.32 Since modern birds probably descended from bipedal therapod dinosaurs, wings with feathers could have been employed for regulating heat—holding them close to the body would retain heat, stretching them out would release heat.33 In the Galápagos Islands I have seen flightless cormorants returning to shore after diving for sea food, upon which they stretch out their stubby little wings with desultory feathers to dry them out and collect heat from the sun. In this case, wings evolved from flight tools to thermoregulation devices. In evolution, structures can be adapted for one function and evolve into use for another function and may have multiple functions at one time.
Another function for wings and feathers recently discovered is as an aid to running—some modern birds flap their wings to gain traction when running up steep inclines, even enabling them to climb straight up a 90-degree vertical structure.34 Yet another function for incipient wings on bipedal dinosaurs was grasping. The most famous transitional fossil in evolutionary history, Archaeopteryx, has wings whose surface area is large enough to support its body in flight, asymmetrical feathers capable of attaining lift, and a shoulder that allows enough flexibility for an adequate upstroke of the wing necessary for flight. Nevertheless, Archaeopteryx retains many dinosaur features, including a functional grasping hand, for which the “wing” was probably originally adapted, and only later exapted for flight.35
Similar reasoning explains the incipient stages in the evolution of eyes, the flagellum motor, and the other structures claimed by Intelligent Design advocates to be inexplicable through evolutionary theory. For the human eye, it is not true that it is irreducibly complex, where the removal of any part results in blindness. Any form of light detection is better than none—lots of people are visually impaired by a variety of different diseases and injuries, yet they are able to utilize their restricted visual capacity to some degree, and would certainly prefer this to blindness. And natural selection did not create the human eye out of a warehouse of used parts lying around with nothing to do, any more than Boeing created the 777 without the ten million halting jerks and starts beginning with the Wright brothers.
As for the bacterial flagellum, although it is a remarkable structure, it comes in many varieties of complexity and functionality. Bacteria in general may be subdivided into eubacteria and archae-bacteria; the former are more complex and have more complicated flagella, while the latter are simpler and have correspondingly simpler flagella. Eubacterial flagella, consisting of a three-part motor, shaft, and propeller system, are observedly a more complicated version of archaebacterial flagella, which have a motor and a combined shaft-propeller system. To describe the three-part flagellum as being irreducibly complex is just plain wrong—it can be reduced to two parts—and disingenuous. Additionally, the eubacterial flagellum turns out to be one of a variety of ways that bacteria move about their environment.36 For many types of bacteria, the primary function of the flagellum is secretion, not propulsion. For others, the flagellum is used for attaching to surfaces and other cells.37
As to whether the flagellum is a product of evolution, eubacterial and archaebacterial flagella share similar structures owing to similar ancestry (known as homologies); there are also homologies between flagellar proteins and other systems, and functional similarity between the secretory systems and the propulsion systems of both eubacterial and archaebacterial flagella. Such similarities point to evolutionary development. We also know that eighteen to twenty genes are involved in the development of the simpler two-part flagellum, twenty-seven genes make up the slightly more complex Campylobacter jejuni flagellum, and forty-four genes exist in the still more complicated E. coli flagellum—a smooth genetic rise in complexity corresponding to the complexity of the end product. Finally, phylogenetic studies on flagella indicate that the more modern and complex systems share common ancestors with the simpler forms.38 So here an evolutionary scenario presents itself: archaebacteria flagella were primarily used for secretion, although some forms were exapted for adhesion or propulsion. With the evolution of more complicated eubacteria, flagella grew more complex, refining, for example, the two-part motor and shaft-propeller system into a three-part motor, shaft, and propeller system that was then exapted for more efficient propulsion. Complex science reduced to evidence for evolution!
The Conservation of Information: Evolution cannot increase specific information content and complexity of organisms, or, there is No Free Lunch.
One of the most scientifically ambitious claims of Intelligent Design is William Dembski’s Law of Conservation of Information (LCI), which is related to his analysis of complex specified information (CSI), an implicit ingredient in the four arguments above. LCI states that “natural causes are incapable of generating CSI” and that “the CSI in a closed system of natural causes remains constant or decreases.” Dembski sets an upper limit to specified complexity generated by law and chance, which he calls the Universal Probability Bound (UPB), which he sets at UPB = 1/2Χ10-150, or about 500 bits of information. If the probability of a specified event is less than the UPB—that is, if it is over 500 bits of information—then it cannot be attributed to law or chance. By the logic of the Explanatory Filter, intelligent design is the best inference.39
This is quite a brainful, so restated, the Law of Conservation of Information says that natural causes such as chance and evolution cannot increase the complex specified information content of an organism beyond 500 bits of information. Since almost all living organisms contain more information than the Universal Probability Bound allows, without the insertion of complex specified information into living forms by an Intelligent Designer, the evolution of complex life is impossible.
Dembski’s principles are embedded in a larger series of what he calls the “No Free Lunch theorems”—as though evolutionary theory were an attempt to grab a perk from the universe without paying for it. “The No Free Lunch theorems show that evolutionary algorithms, apart from careful fine-tuning by a programmer, are no better than blind search and thus n
o better than pure chance,” and “the No Free Lunch theorems show that for evolutionary algorithms to output CSI they had first to receive a prior input of CSI” from an Intelligent Designer.40 So confident is Dembski in his Law of Conservation of Information that he proposes it as a candidate for the Fourth Law of Thermodynamics.41
Dembski’s Law of Conservation of Information is purposely constructed to resemble such physical laws as the conservation of momentum or the laws of thermodynamics. But these laws were based on copious empirical data and experimental results from the real world, not inferred from logical argument alone as Dembski’s law is. Further, no other recognized theory of information—such as that proposed by the mathematician and information pioneer Claude Shannon—includes a law or principle of conservation, and no one working in the information sciences today uses or recognizes Dembski’s law as scientifically useful, regardless of its design inference.
Even if Dembski’s LCI were validated, it is irrelevant to the theory of evolution, because it is abundantly clear that information in the natural world—through DNA, for example—is transferred and increased by natural processes. Microbiologist Lynn Margulis, for example, has demonstrated that complex eukaryote cells, such as those of which we are made, evolved from simpler prokaryote cells. The genomes of eukaryote cells increased in size—and thus in complex specified information—by incorporating simpler genomes of prokaryote cells.42 Intelligent Design theorists respond to this by saying the Intelligent Designer created complex eukaryote cells. If that is so, why does it appear that the Intelligent Designer cobbled these cells together out of parts lying around in the pre-Cambrian soup? In fact, complex eukaryote cells are a grab bag of goodies from the prokaryote world, including mitochondria, which contain their own genome. Ever heard of mitochondrial DNA (from which human lineages may be traced through females)? Our cells already have a nucleus containing a complete genome. What is another genome doing in our mitochondria? Evolution offers an answer: They are vestigial features of eukaryote cells that evolved from prokaryote cells. Intelligent Design, in contrast, offers nothing more than “then a miracle occurs.”