5X5 Episode 83
|5X5 Episode 83|
|20th December 2009|
|5X5 82||5X5 84|
|S: Steven Novella|
|R: Rebecca Watson|
|B: Bob Novella|
|J: Jay Novella|
|E: Evan Bernstein|
You're listening to the Skeptics' Guide 5x5, five minutes with five skeptics, with Steve, Jay, Rebecca, Bob and Evan.
S: This is the SGU 5X5 and tonight we're talking about irreducible complexity. Irreducible complexity is a notion that was first put forward by Michael Behe, an intelligent design proponent, to argue that certain structures in biology are so complex that if they were simplified any further, they could not function. They contain multiple interactive parts and if you take any one part away, the overall system doesn't work. Therefore, he argues, it could not have evolved from simpler structures because those simpler structures could not possibly function and therefore could not be selected for through Darwinian processes.
R: One example he uses is the mousetrap analogy, which is the idea that a mousetrap wouldn't work with any of its parts removed. So take away the spring, you've just got a useless piece of wood and a piece of metal. But of course, this fails to take into account the idea that parts can have uses other than the current end use. So you could use the pieces of a mousetrap to do something else if not catch a mouse. So if you look at the evolution of certain body parts, they might have had another function before they evolved to their current function.
E: And actually, before Behe, irreducible complexity is not in itself a new concept. It was cited almost two thousand years ago, from the first century. Galen, a physician at the time, wrote about large numbers of parts of the body and their relationships, which was often cited as evidence for creation, and through the years and through the centuries there were more examples of this coming up in the literature. Late 17th century, Thomas Burnet referred to a "multitude of pieces aptly joined" to argue against the eternity of life. Also, William Paley in his book Natural Theory discusses at length what he called "relationships of parts in living things" as indication of their design. Right up into the 20th century, in which we had publications of books in the 1970s, such as young earth creationist Henry Morris, who broke down the concepts of irreducible complexity as scientific creationism, and correlating mathematics to it, to show that the probability of evolution through natural selection did not mathematically hold water.
B: One of my favorite examples of irreducible complexity is something that the IDers will still talk about to this day, and that's the evolution of the eye, of the human eye. Their argument goes something like this: "How can an eye evolve slowly over time? It would be useless until the final piece evolved. Until then, it would be as useful as half a tractor. If it were any simpler, it wouldn't work. It is therefore irreducibly complex." Even Darwin refuted this argument over 150 years ago when he pointed out that animals with eyes simpler than humans' exist and yet they're still perfectly functional. But these people don't realize, or they don't wanna realize, that the eye was useful to the organisms at every step of the way through evolution. And this isn't idle speculation, either: scientists have found a whole range of eyes in nature, ranging from very primitive, just a patch of skin that's sensitive to light, to maybe a small pit in the skin that can reveal the direction that light's coming from, or even to eyes with very primitive lenses that focus light. And all the way obviously to the complex eyes we find for humans and other animals in nature.
J: Bob, your example of the eye is a large version, and there's also very, very small versions of irreducible complexity, like the flagella—this was another thing that Behe had attacked as an example. The flagellum that they were looking at&mdsah;it had about forty complex protein parts, and together they would form what they called an engine and that would allow the flagellum to move around. And they found that the proto-flagellum can act as a piercing mechanism for the bacteria.
B: Which goes back to what Rebecca was saying, that evolution takes bits of an organism and co-opts it, taking one use and turning it into another use. Over time you would never... it would be very hard to say what other uses these things might have had.
S: And to clarify, the examples we're giving, we said these were examples of irreducible complexity. They're examples of alleged or proposed irreducible complexity. But they have all been blown out of the water by further scientific investigation. And Michael Behe and other intelligent design proponents do completely ignore or dismiss the arguments against the very concept of irreducible complexity. They simply ignore mechanisms that are known to exist in evolution that render the notion of irreducible complexity nonsensical. We mentioned one: Behe assumes that an allegedly irreducibly complex structure had to have evolved to its current utility, when in fact we know that structures evolve through different utilities. As with the flagella it could be first used as simply a mechanism to inject toxin into another bacterium and then later can add pieces that will give it some other functionality.
There's other mechanisms as well; for example, there is gene duplication where there may be absolute redundancy. An organism can have two genes for the same protein so that one gene can continue its original function while the duplicate copy of the gene is free to experiment and evolve in novel directions and take on new utility.
And as with the example with the eye, simpler versions of structures can function in a more crude but still valuable way. An eye patch still will tell you what the direction of light is. I always liked the example of dragging around half a tractor because that example actually—you can turn that against them. In fact, that's the wrong analogy. People were not dragging around half a tractor a couple hundred years ago—they were dragging around a plow. The plow worked, it was much simpler, but it got the job done and then plows became more complex. At first they were just a piece of metal and then they were more and more shaped; you could have multiple plows together; the shapes evolved to be more efficient. And then later—this is now, of course, examples of technological evolution not biological evolution—and then later we had very simple tractors that then themselves got more and more complex over time. But each step of the way you had a functioning useful thing, so our evolutionary ancestor didn't have half an eye any more than people were dragging around half a tractor. You know, there were plows and there were eye patches, and both were simpler, cruder but got the job done, and could be selected for through evolutionary Darwinian mechanisms.
So essentially, the concept of irreducible complexity is completely flawed and totally refuted, but that does not stop intelligent design proponents from continuing to use it.
S: SGU 5x5 is a companion podcast to the Skeptics' Guide to the Universe, a weekly science podcast brought to you by the New England Skeptical Society in association with skepchick.org. For more information on this and other episodes, visit our website at www.theskepticsguide.org. Music is provided by Jake Wilson.