Irreducible complexity and evolution
An article came to my attention last week, on the evolution of a hormone and its receptor. It would appear that such a system is an excellent example of an irreducibly complex system – each is useless without the other, and anything that depends on the hormone and receptor working properly in order to function is useless unless both the hormone and the receptor are in place and working properly.
Rather than link to the article itself, I’ll point to a couple of articles that deal with the findings and their implications in more depth.
The upshot is that researchers, having assumed that evolution happened, used comparisons of variant forms of a hormone receptor to work out the story of its origin and development over time. Based on the reconstructed history, a receptor that responds to cortisol was accidentally copied, and the copy subsequently changed, through mutation, into a receptor that responds to aldosterone. The amazing part of the story is that the receptor actually evolved before the chemical it responds to.
Well, it’s amazing until you look deeper.
Living fish don’t make aldosterone, and yet it can still attach to fish MR anyway. Obviously, the fish aren’t making these receptors to snag hormones they don’t make. Instead, it seems that in fish, MR are responding to DOC, which is very similar to aldosterone. In the ancestors of tetrapods, DOC evolved into aldosterone and took on its function that it has in our own bodies.
A very popular analogy for molecules and their receptors is a lock and a key. This is good for visualization, but it’s misleading. Molecules bend and stretch, a feature found in only the cheapest and most ill-made locks. It’s common to find that a receptor for one molecule binds quite nicely to another. Carbon monoxide is perfectly willing to bind to hemoglobin in the blood. Indeed, it’s a little too willing to do so. A liver enzyme that breaks down alcohol is perfectly happy to break down ethylene glycol, a component of antifreeze. The problem here is that the liver has other enzymes that clean up the mess left by the first one, so the toxins resulting from breaking down alcohol will eventually go away. The product of breaking down antifreeze won’t react with the next enzymes in the chain, so they don’t get broken down. Eventually, they form crystals in the kidneys, resulting in damage and eventual kidney failure. (The treatment for antifreeze poisoning, by the way, is to keep the patient liquored up. Emergency room handbooks give the dosing schedule to keep the blood alcohol high enough to block the reaction with ethylene glycol, long enough for it to flush from the body.)
Indeed, one bit of wisdom from organic chemistry is, “if the reaction won’t go, spit in it”. Saliva is filled with random bits of protein, and there’s a very good chance that at least a few of them will catalyze the reaction in the test tube. It looks like getting protein to bind with other molecules is easy. The hard part is fine tuning so they react with the one molecule we want affected.
This, along with the piece on blood clotting, is of considerable relevance to the design-vs-evolution debate.
Some of the comments are worth addressing:
Regardless which side of the ID issue I come down on, the autors insistence that the article shown somehow disproves ID or proves a piece of the evolutionary pie is a huge stretch.
and
I do not see any coherent arguemnet to show that the concept of irreduceable complexity is incorrect.
Here, we see a bit of confusion over what claims are being made, and by whom.
The point is, biologists are not trying to prove evolution. As far as they’re concerned, the argument is over. You don’t see papers in biology journals trying to prove evolution any more than you see papers in math journals attempting to prove algebra.
There are at least 50 major journals in the academic field of biology. All accept without question the theory of evolution as I outlined it above. They are not attempting even to prove the theory, any more than math journals attempt to prove that the sum of the internal angles of a plane triangle is 180 degrees, or engineering journals revisit the existence of gravity. But they would be nonsense without the theory of evolution, just as engineering would be nonsense without gravity. Each of those journals is published about four times a year; several of them have been in existence for over a hundred years. Each journal contains at least ten articles of about 2-20 pages, and each of those articles represents several months’ or years’ work by a team of trained biologists whose most compelling material and moral interest would be to disprove the work of all their predecessors and to make an immortal name by doing so. The work of the biological teams is required to be backed up by exhaustive experiment and observation, together with exact statistical analysis of the results. There is a continuous process of search through all these articles by trained reviewers looking for discrepancies among them and demanding new experimental work to resolve them. Since every one of these articles relies on the consistency and truth of the theory of evolution, every one of them adds implicitly to the veracity of the theory. By my calculation, then, opponents of evolution must find a way of matching and disproving, experiment by experiment, observation by observation, and calculation by calculation, at least two million pages of closely reasoned scientific text, representing roughly two million man-years of expert research and perhaps trillions of dollars of training, salaries, equipment, and infrastructure.
(Link)
Likewise, explorations of the blood clotting cascade or the evolution of the hormone-receptor pair mentioned above don’t show that irreducible complexity or intelligent design are incorrect. What they do show is that Behe’s description of an unbridgeable chasm between point A (no hormone, and no receptor) and point B (fully functional hormone and fully functional receptor) is not a permanent barrier. Demonstrating the existence of at least one chain of small steps across (or around) the canyon is enough to prove that you can make the journey on foot.
Demonstrating the existence of a path around the canyon doesn’t disprove the notion that angels picked a person up on one side and deposited him on the other, and demonstrating a series of small steps that lead to an irreducibly complex system in living things doesn’t disprove the notion that an Intelligent Designer engineered the system. All it shows is that a designer who micromanages in this fashion is not required to explain how things came to be.
Now, if researchers haven’t proven evolution, what did they do?
They took evolution as a given, and asked what traces would have been left by an evolving system. They came up with educated guesses as to what these traces would look like, and where they’d be found, and then they looked to see if these traces could be found.
Ninderthana comments:
The liklihood that the over 200 seperate reactions that are needed to make blood clotting work came together by chance is so small that it far more likely that the universe will turn into a pile of marshmellows in the next nano-second.
(Snarky response: “show your work”.)
More serious response: This is a bogus argument (also known as the “tornado in the junkyard” argument.) No scientist believes the entire sequence came together as the result of 200 (or whatever the right number is) separate reactions flying together at once. Indeed, the whole point of the research was to show how complex systems developed from simpler systems, piece by piece, over generations. In each case, we see that the intermediate steps do work, at least well enough for the creatures using them at the time.
The explanation that blood chain came about because of deliberate design is much more plausible.
If this chain existed in only one form, you might be right. The problem is, it exists in many different forms. And in simpler organisms, we find chains with one or more of the links missing. An intelligent designer may be the simplest explanation if every animal with a clotting system had the exact same design, and no animal existed with even one part of this design missing, but that’s not what we see. What we do see is countless animals with very workable intermediates between our clotting system and the makeshift design found in lobsters. The deliberate design explanation becomes a lot more complex when we try to explain why a designer would have created all those intermediate designs, and put them in animals exactly the way biologists would expect to find them, if humans and lobsters had a common ancestor.
In Behe’s chasm analogy, it’s equivalent to researchers figuring that if someone crossed from one side to the other using a particular pathway, there should be footprints. So they look along the path the person might have used, and lo and behold, here’s a shoe print in a spot the wind hasn’t touched yet. As you look along the pathway, maybe you find some partial footprints here and there. Then as technology improves, you find hairs and flakes of skin, and match the DNA to the person who crossed the chasm.
Still no proof that the person was not carried across by angels. After all, the angels could have created the footprint on the supposed path. But when enough evidence, consistent with the theory, is found, it’s simpler to believe the person walked along the path we’ve found than to believe in angels busily creating all kinds of spurious evidence.
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April 13th, 2006 at 12:29 pm
[...] Irreducible complexity and evolution [...]
April 13th, 2006 at 6:31 pm
>>>>You don’t see papers in biology journals trying to prove evolution any more than you see papers in math journals attempting to prove algebra.
April 14th, 2006 at 4:41 am
Karl,
Isn’t it just possible that a “designer” [Note: I am not claiming any devine nature to this designer] created a set of basic rules which include, amongst other things, the possibility of variation and chaos that can allow for subsequent change and evolution.
You are right to point out that there are a number of blood clotting cascades but it is very plausible that these variations
are just a “tweeking” of the orginal design.
The reason why I still insist on the claim that design is more likley is based on the simple fact that to bring together hundreds of reactions that appear to have no function in any subgrouping, has such an implausaibly low probability as to be farcical. Even if you allow the hundereds of time the age of the universe, the probability is infinitesimally small.
Why do you insist on believing that something that has the same probability as the toot fairy being real, is a proven scientific fact.
Evidence of evolution exists all around us both in its macro and
micro forms, however, just because evolution exists, does not mean that it successfully describes all of the observations and phenomenon in the biological Universe.
You have only to look at Physics to see that theories which were once regarded as rock solid and firmly backed by hundreds of years of scientific consensus are now known to be inperfect or incomplete descriptions of reality. Many of these changes in physics have not involved the complete abandoning of old ideas but a realization that these theories were limited. For example, Newtonion mechanism is perfectly useful as long as you don’t approach the speed of light or try to investigate things on very small scales.
I feel that biologist have not yet learned the lesson that physicists learned long ago. Evolution, does appear to describe many
of the biological phenomenon that we see in the world around us. However, at the biochemical level, there are claring examples of irreducable complexity that are extrenely difficult to explain.
To try and dismiss these examples by adhering to a blind faith
that somehow a little more reasearch and understanding will make them go away is missing the point completely. Just as the lack of ether lead Einstein rethink the way we look at the physical Universe, the case of irreducable complexity that are popping up
at the biochemical level, will force us to rethink the way we look at the biological world.
As to your notion that scientific consensus does not allow people to investigate anything outside the box of evolution, I could not disagree with you more.
Of course we have to use the tool of “scientific concensus” to guide us in our investigation of the Universe. But any good scientist should know that it is a tool that we use to conduct our science. However, it is not a rule of natural law. We should be constantly aware of the fact that sometimes the consensus view [no matter how ell established] blinds us to alternative but scientifically reasonable ways of seeing the Universe
April 14th, 2006 at 3:41 pm
Ninderthana:
It sure is. In fact, when scientists set out to design artificial life forms, they use a process of inducing random variation and selecting among the variant forms for the “fittest”, based on whatever criteria they have in mind.
The crux of the debate lies in what the basic rules are, and what they cover. Evolutionists believe the basic rules cover everything, and the Intelligent Design movement believes they don’t. In effect, they believe the Designer was not capable of designing a system that worked without constant tinkering.
April 14th, 2006 at 3:51 pm
Ninderthana, there is one thing here you don’t seem to get. It’s something a lot of people don’t get, but it puzzles me each time I run in to one of those people. You write:
I’ll repeat what I wrote in the main post: No one believes hundreds of reactions had to come together all at once! (Maybe you should repeat that back to me, so I know you read it.)
Here, for example, is a link to a detailed description of how the blood clotting system could have come together, piece by piece, with no requirement that the entire system come together in one hugely improbable scrunch.
When ID advocates say that some system is irreducibly complex, they’re probably right. When they say it can’t have been formed by the mechanisms known to evolutionary biology, they have this nasty habit of being proved wrong.
Now, there’s no proof that the blood clotting system had to come about the way this document describes. But to rebut the ID claim that evolving the clotting mechanism is impossible, all that is needed is to show one way that it is possible.
April 15th, 2006 at 5:52 am
When they say it can’t have been formed by the mechanisms known to evolutionary biology, they have this nasty habit of being proved wrong.
“Proved” is a word I thought evolutionists never used. It’s all theories, I was led to believe. If you people didn’t want to believe this malarky so fervently, you wouldn’t likely be so easily fooled.
April 17th, 2006 at 5:26 pm
Hal writes:
When you say “it’s all theories”, I suspect you’re using a faulty definition of “theory”.
A theory is not a guess or a hunch. A theory is a model intended to explain large bundles of facts. Newton’s theory of gravity was intended to explain a huge number of phenomena which had previously been explained using a whole bunch of separate models.
Evolutionary theory is intended to explain the diversity of life, the similarities living things share, the geographic distribution of life forms that appear closely related, and the distribution in time and space of fossilized life.
Now, here’s what people seem to have a hard time getting about science.
No model can ever be proved right.
Any model can be proved wrong.
As this article states, this theory is tested every time a biologist carries out research in his field, and the results of the test appear in the journals. Every research paper is a chance for evolutionary theory to be proved wrong.
The Intelligent Design Movement makes a few predictions, mostly along the lines of “no one will ever come up with a way to make biological system X through a series of small, evolutionary changes.” These predictions are proven false every time someone comes up with a way of evolving such a system.
None of these investigations can prove that evolution is right. For all we know, there’s a Creator working magic behind the scenes, in such a way that it looks like natural laws at work. But when someone predicts X and instead we observe Y, well, then it’s very easy to say the prediction has been proved wrong.
A good example, and something I think I can safely say we would agree on, is the track record of psychics.
Jeanne Dixon used to claim a high rate of accurate predictions – something like 70 or 80 percent.
Every winter, one or another tabloid would publish a bunch of predictions for the coming year. It was a very simple exercise to keep these predictions and compare them with subsequent events, and see how many of them came to pass. You might have the janitor make a similar number of predictions as a control.
Typically, Jeanne Dixon’s record was pretty terrible, and in no event, any better than the record of the janitor.
In essence, the argument is made, “If Jeanne Dixon is psychic, a large number of her predictions will be correct.” We count up the correct predictions, and find that only a small number are correct. This disproves the contention that a large number of predictions are correct, which – by operation of the rules of logic – disproves the claim that Jeanne Dixon is psychic.
If her predictions were accurate, would this prove she’s really psychic?
No.
All we’d have, given a large number of correct predictions, is that it’s consistent with psychic ability.
But it’s also consistent with cheating, lucky guessing, inside information, or even having been fed the answers by an Intelligent Designer. It’s even consistent with the existence of an Intelligent Designer who has a crush on her, and redesigns events to make them match her predictions.
Science can never prove a theory true. All it can do is make an inductive case, showing that test after test fails to disprove it. Science is perfectly capable of proving a theory false, by producing observed facts that contradict it.