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Unixman

4 bar joint in knee

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I got into a discussion at work (fool me) with a person who turned out to be a IDer who unfortunately is also an aerospace engineer who went on about the evolution of the 4 bar link in the knee. he basically said that a 3 bar or a 2 bar link just won't work and it has to be a 4 bar link. Hence the ID bit ...

 

Now my background is not in anatomy but rather biochem/molecular biocogy so I really don't have a particular idea on how the knee evolved ....

 

Anyone know?

 

To my irritation most of the google links point to ID sites :-(

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He is correct, there was never a "3 bar" or "2 bar" joint.

 

Source

 

Within the first paragraph of that source it explains quite nicely:

"The irreducible mechanism of the knee joint is shown to contain at least 16 critical characteristics, each requiring thousands of precise units of information to exist simultaneously in the genetic code. This demonstrates that the knee could not have evolved but must have been created as a fully functioning limb joint from the beginning of its existence."

 

I understand, that here, it doesn't talk specifically about the 4 bar knee joint, but that's besides this point.

Edited by Neco Vir

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The entire irreducible complexity argument is completely fallacious and has been rejected by the majority of the scientific community. The fact that this argument was not accepted scientifically was even recognized by a judge who stated in the case Kitzmiller v. Dover Area School District:

 

We therefore find that Professor Behe’s claim for irreducible complexity has been refuted in peer-reviewed research papers and has been rejected by the scientific community at large

 

When the structure and physiology of the knee is looked at in the right way it actually provides a good case for the theory of evolution from common descent. Which is explained by Dr. John R. Hutchinson:

 

Claim: The chance of the four bar mechanisms of the human knee joint occurring by evolution is zero. There are too many changes that have to occur simultaneously.

 

John R. Hutchinson: “This ‘irreducible complexity’ argument makes numerous fatal flaws. An important one is that evolution proceeds by using old structures for new functions. It is thus a logical fallacy that the changes must occur simultaneously. Furthermore, the “four bar linkage” system of the “human” knee is seen (with subtle or striking variations) in virtually all land-dwelling four-limbed vertebrates (tetrapods), and so it is not an exclusively human feature. Our system shows subtle modifications of the general tetrapod theme that are specializations for bipedalism from a more primitive system of ligaments, but still reveals the community of descent in its common structure. Considering the similar (but varying according to function) morphological patterns in these ligaments, this is actually strong evidence for evolution.”

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I find it unscientific to claim that an effect (ie, the 4-bar knee joint) can result from only one cause (ie, ID) because this insinuates that all causes (typically an infinite number) were tested and failed. To me, these ideas that "it can only be caused by ID" are wholly without substance and can be summarily dismissed. Besides, if the knee is the "perfect" joint for humans, why does it suffer from so many problems? :blink:

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I must be dumb or something. The 4 bar linkage refers to 4 rigid links. The knee has 2 bones which are rigid and a whole bunch of ligaments and stuff that are flexible.

Can someone please tell me what part(s) of the knee is meant to be a 4 bar link?

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From memory there are four bones involved in forming the knee join: femur, tibia, fibula and patella. The four bar linkage is simply established between femur and tibia with linkages by ligaments, though. At least, if I recall correctly. It has been a long, long while since I last worked with something that had knees....

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