God Riddance

 

Irreducible Complexity

 

Perhaps the most interesting argument turned out by the Intelligent Design community is the argument from “Irreducible Complexity”. The argument is a stronger, more rigorous version of a very old creationist argument which is that some organ, like the eye or wing, is just too complicated to have come about by the trial and error process of natural selection. Surely an unintelligent process could not create something which intelligent beings like us marvel at! It is usually argued that some organ, system, or biological structure would not be any good to a creature unless the entire multipart system was present. Since evolution can only work through small steps, favoring only what is useful to the organism at the time, such multipart systems could not evolve.

As should be expected, Evolutionary Biologists, beginning with Charles Darwin, have been curious about such complexities of nature and have searched for testable, scientific explanations of how these complex systems came to be. In the sixth chapter of Origin of Species, Darwin even admitted that the eye seemed to be a threat to his theory:

 

“To suppose that the eye with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest degree.”

 

But Darwin immediately went on to explain how this problem could be solved:

 

“Reason tells me, that if numerous gradations from a simple and imperfect eye to one complex and perfect can be shown to exist, each grade being useful to its possessor… Then the difficulty of believing that a perfect and complex eye could be formed by natural selection… Should not be considered as subversive of the theory.”

 

Darwin then went on to list many simpler and more imperfect eyes found in the animal kingdom: The starfish, for example, has only a depressed region of light sensitive cells. Today we know of even simpler eyes, such as light sensitive pigments found in single celled organisms[i]. We can easily imagine how photosensitive pigments give rise to photosensitive cells in multi-cellular organisms, and how more photosensitive cells give the organism a greater sensitivity to light. We can further imagine an organism evolving a patch of photosensitive cells, and further evolving a depressed patch of these cells (as the mollusk Patella has). The next evolutionary step would be for this photosensitive depression to acquire an outer covering of ordinary cells for protection (This is the simple eye that the mollusk Nautilus has). Once this has happened, it is essentially just a matter of evolving the right types of “outer coverings” (the lens, the eyelid, and so on) before the evolution of the human eye is complete[ii].

I apologize to the reader if my account of the eye’s evolution seems too abrupt, but rest assured that many have described it in much fuller detail than I have[iii]. For example, two scientists have broken the evolution of the eye into two thousand steps[iv] and calculated a “pessimistic estimate” of how long it would take before the eye evolved. Their answer? Only a few hundred thousand years[v], which is an extremely short period of time, given that animal life has existed for hundreds of millions of years.

And what about the wing? If a partially developed wing is no good for flying, how could natural selection have favored it? Scientists have discovered that a primitive wing is excellent for body heat regulation in small animals, such as birds and insects[vi]. Once this primitive structure has reached a large enough size, it maxes out its use for heat regulation and begins to be useful for something else: flight.

I once met a creationist in a bookstore, and we (of course) ended up discussing evolution. Like most creationists, he was ready to take on evolution with an example of something he thought could not be evolved. He explained to me that there is a species of woodpecker that pecks wood with such force that its eyes would pop out if it did not close them when pecking (I haven’t been able to find a source for this claim, but for the sake of argument I will assume it is true). How would something like this evolve? The woodpecker would need to evolve the instinct to close its eyes before pecking, but this instinct would do no good unless the woodpecker had already evolved to peck wood, which would seem extremely unlikely if this caused his eyes to pop out (birds that do such self destructive things would not be expected to be favored by natural selection). But what if the woodpecker began pecking wood at a much less rapid rate, so that its eyes remained securely within its head? It could then evolve the instinct to close its eyes (which would be useful, not because it kept the woodpecker’s eyes within its head, but because it kept specks of wood out of its eyes which could cause eye damage or infection). Once it evolved this instinct, it could then evolve to peck wood much harder than before, since now there would be no danger in losing his eyes.

Creationists cannot understand that some things may have originally had a different function, and so they mistakenly conclude that an evolutionary predecessor (“half a wing” or “half an eye”) would not be favored by natural selection. Co-option, the idea that something can gradually evolve a new function, is central to understanding biological complexity. If we see a biological structure, and we notice that it is useless when we take away one of its parts, we need to ask ourselves whether it really would be useless: Can it serve another function?

In 1996 the biochemist and intelligent design proponent Michael Behe authored Darwin’s Black Box – A book which attempted to revive the old argument from complexity, but with a few new twists. Behe argued that some microscopic cellular systems are useless unless the entire system is present[vii]. It is argued that since no single mutation could produce these systems, and since evolution has to work by taking small steps (more on this in chapter 9), evolution by natural selection cannot account for such a system. It is further argued that since such irreducibly complex objects are, in our experience, always produced by an intelligent agent (think of a TV which does not work without all of its parts), we should prefer the explanation of intelligent design for the irreducibly complex systems we find in Biology.

Two of Behe’s infamous examples of irreducible complexity are the blood clotting system and the bacterial flagellum. The problem with these examples, however, is that you can take away multiple parts and still have a functioning system. For example, puffer-fish and dolphins lack several of the blood clotting factors found in most other vertebrate animals[viii] and yet they manage just fine.

Another major problem for Behe’s argument is that scientists have provided a detailed scenario for the evolution of the bacterial flagellum[ix]. It turns out that you can take away parts from the flagellum and still have a functioning system. The trick is that the system has evolved brand new functions throughout the course of its evolution. For example, the type three secretion system, which is thought to be an evolutionary predecessor of the flagellum, does not function for locomotion (Like the bacterial flagellum). Instead, it functions to inject toxins into cells.

How does the intelligent design community respond to these charges? In the case of the blood clotting system, ID proponent Casey Luskin[x] has argued that it isn’t the entire blood clotting system which is irreducibly complex; Rather, there are certain core parts of the blood clotting system which comprise an irreducibly complex system. However, recent research has shown that some of the factors Luskin deemed part of the “irreducible core” (Clotting factors V and VIII) are represented by only a single gene[xi] in Jawless fish. This means the two factors deemed necessary by Luskin actually aren’t; They evolved from a single ancestral gene which is present even today in the Lamprey fish.

In the case of the bacterial flagellum, Michael Behe realizes that it is possible for such a system to evolve through an “indirect” route (That is, for an irreducibly complex system to evolve from parts which previously served a different function). However, he argues that the parts making up such systems, even if pre-existent in the cell and serving some secondary function, could not be combined into an irreducibly complex system because each part would be specified for its current function and may not be suited to the new function. Behe provides us with an analogy to help us understand what he is arguing:

 

“[S]uppose you wanted to make a mousetrap. In your garage you might have a piece of wood from an old popsicle stick (for the platform), a spring from an old wind-up clock, a piece of metal (for the hammer) in the form of a crowbar, a darning needle for the holding bar, and a bottle cap you fancy to use as a catch. But these pieces couldn’t form a mousetrap without extensive modification, and while the modification was going on, they would be unable to work as a mousetrap. Their previous functions make them ill-suited for virtually any new role as part of a complex system.”[xii]

 

Philosopher Paul Draper[xiii] provides an excellent counter to Behe’s argument: Although Behe’s analogy illustrates his point well, Behe has not shown that any biochemical “part” must possess a great degree of specificity before it could perform a new task. Perhaps when these allegedly irreducible systems first evolved, the parts could perform their task, but not efficiently. These parts could later be modified by natural selection to work more efficiently.

Draper also provides a good argument that Behe’s conclusion is premature. Scientists are still in the process of figuring out how many of these intracellular systems work, so why would anyone demand an in-depth explanation of how these systems evolved? A reasonable position would allow scientists to continue their work, and, if Darwinian explanations are not proposed after scientists fully understand these systems, perhaps we should turn a skeptical eye on evolution. But that day has not come.

Before I conclude, I’d like to point out two things: (1) That simplicity, not complexity, is the hallmark of intelligent design, and (2) That mind boggling complexity is expected from the process of evolution. To see what I mean, let’s look at evolutionary algorithms. An evolutionary algorithm is a computer program which simulates the process of natural selection in order to solve a problem. For instance, a genetic algorithm may simulate an imaginary species of television sets which has the ability to reproduce. There is random variation within the population of television sets (as there is within real species in nature), and the television sets with variations that make them better suited for watching (Like a clearer image) are allowed to leave behind more baby televisions than the variations which make the sets worse for watching. So the best TV sets will become the most common. In addition, since there are random changes made in every generation, it allows for positive cycle: Each time a good variation arises, it becomes common. Then another good change takes place and becomes common. This means that after so many generations there is a build-up of lots of good changes from the original TV Set.

The process which I have just mentioned has been used with great success in many different fields[xiv]. In one case, it was used in electrical engineering to evolve a voice recognition device. Ironically, the scientist who set up the process of its evolution has found that, after several hundred generations of evolution, the device has evolved so much complexity that he is unable to figure out how it works[xv]!

---