Is the human knee joint “irreducibly complex”?

This is a re-post, in slightly modified from, of one of my Talk Origins Archive feedback responses (from back when the Archive had a feedback section, specifically March of 2002)

Luke asked:

Please email me your response if possible. I don’t want to categorize myself as a evolutionist or creationist. I was visiting the other website I think it was creationist or similar, your guys arch enemies; anyways I was trying to find proof to support modern man evolving from ape, and they had an extensive article written about the human knee and how it has sixteen parts and minus just one and its useless. Apes have non locking knees and because of their makeup you aparently can’t evolve it into a locking one you have to start from scratch. Evolution and mutations from what I’ve read only allow for small changes no mutation can allow for the formation of a complex organism with sixteen moving parts? The knee would have to be built all at once it couldn’t evolve or it would have no use. How do you suggest that apes dumped their knees and immediately mutated new ones with sixteen brand new parts? I would like to believe it could happen just seems far fetched?

This argument originates from an article (Critical Characteristics and the Irreducible Knee Joint) published in the Creation Ex Nihilo Technical Journal (Vol. 13, No. 2, 1999) by a British engineer named Stuart Burgess.

From my reading of the article it seems to be highly flawed, especially in its almost total lack of discussion on the comparative anatomies of living non-human apes (gorillas & chimps etc.), extinct hominins (australopithecines, early Homo) and modern humans. This lack of attention to comparative anatomy (and physiology) is typical of anti-evolutionists and it leads them to continually talk about the anatomy/physiology of various organisms as if they exist in a vacuum (examples: The woodpecker or The bombardier beetle). They focus on some extreme example of organ or system in a particular species as if it is totally unique to that species. The fact is that when one looks at other closely related species one usually finds that there are variations on the extreme example that the anti-evolutionists have focused upon.

For instance the bombardier beetle that anti-evolutionists often cite is just one species of a whole group of beetles (“Ground beetles”, Family Carabidae) many of which have some variation on a chemical defense mechanism, using the same basic chemicals (which exist in many beetles in varying amounts), but used in differing ways. The specific example that anti-evolutionists cite sprays an explosive mixture out of its abdomen in a fairly well aimed stream at its attackers, however there are other Carabid beetles that spray with less accurate aim, and others that merely excrete bad tasting chemicals out of their abdomens when attacked. There is a whole spectrum from fairly simple to fairly complex defense mechanisms. Anti-evolutionists only talk about the more complex variant.

This discussion of the human knee is another example of this sort of argument in a vacuum.

While I am not an expert in the comparative anatomies of the living non-human apes and humans, as far as I am aware there is no material difference between them. That is, every bone, muscle, ligament, tendon, and cartilage in the human knee has its corresponding representative in the knee of chimpanzees and the other great apes (and presumably in the knee of their concestor). Yes they are shaped somewhat differently. Yes they are proportioned differently. But as far as I know all the same parts are there (if there are any primatologists or physical anthropologists out there, please correct me if I am wrong). [Note: see the 2nd Lovejoy quote provided by Adam Benton in the comments section below.]

As for fossil hominins, the knees of more derived types like Homo erectus (which are either “fully human” or “just apes” depending on what anti-evolutionist you talk to) seem to be virtually identical to those of H. sapiens. As for the knees of the more basal species of Homo (H. habilis) and the australopithecines these become increasingly like those of living non-human apes the farther back in time one goes. Exactly the sort of thing one would predict if humans evolved from an “ape-like” ancestor. The knee of Australopithecus afarensis (which most anti-evolutionists say is “just an ape”) retains a number of “ape-like” features but also has characteristics like those of later hominins including H. sapiens. In other words it is an intermediate form in this regard.

The knee bones of a modern human, an australopithecine and a chimpanzee.

See The ICR and Lucy: Bearing False Witness Against Thy Neighbor for more comparative photos, or refer to any good text on human evolution for comparative illustrations.

Burgess does mention living apes briefly but only to dismiss them as being poor bipedal walkers. However this is a problem for his argument for irreducible complexity (IC), at least as I understand Michael Behe‘s (the person responsible for the recent popularity of this term) definition of the term, in that while the knees of living non-human apes are slightly different in form, and are not as efficient for use in bipedal walking as those of humans, they do work, and they can walk bipedally.

Note: please remember that evolutionary theory does not postulate that humans are descended from other living apes, like chimps or bonobos, rather we share a common (ape) ancestor with those species.

So, assuming that knee joints of the ancestor of later hominins was essentially the same as those of the living non-human apes and could, like them, walk in a bipedal manner at all, then it would be possible for there to be a selective advantage for any slight modifications in their descendants which lead towards an increase in efficiency of bipedalism.

The human knee seems to me to be a poor example of an IC structure.

Some of Burgess’ other arguments just seem nonsensical to me. For example he states:

The knee joint presents a major challenge to the evolutionist because it is unique, and because there are no intermediate forms of joint between a condylar joint and the other two limb joints found in animals and humans – the ball and socket joint and the pivot joint. (Burgess, 1999)

I fail to understand Mr. Burgess’ challenge here. Knee joints did not evolve from elbow, shoulder, or hip joints. Rather knee joints have been knee joints since their origin in the first tetrapods. The same applies to the other types of joints. So why would we expect to find “intermediate forms” between them? That Burgess even poses this as a supposed problem for evolution demonstrates a significant lack of understanding about evolutionary theory and the fossil record.

Ichthyostega; an early tetrapod and its hind leg bones. Its “knee” was the joint between the femur and the tibia and fibula.

It is a curious thing that Behe’s principle of IC as an argument for design turns the traditional argument from design on its head. It used to be argued that those features of organisms that seem perfectly sculpted to suit their needs, or seem well designed from an engineering point was evidence for design. Now, under Behe’s IC principle of design, it doesn’t matter how clunky, ungainly, and poorly designed from an engineering point of view something is, it only matters that it is supposedly irreducibly complex.

Apparently the “Designer” under this new design “theory” is a (supernatural) cosmic Rube Goldberg.

Related Links

A lizardy day

The weather was nice today (Sunday 4-22-12); sunny but not too hot, so I spent a couple hours over at my parents’ house today wandering around the yard looking for critters like I used to do when I was kid. Only this time I was armed with a camera instead of a jar or coffee can, intending to capture images rather than bodies. My target was the host of lizards that have taken up residence in my parents’ yard; specifically Western fence lizards (Sceloporus occidentalis).

When I  was a kid used to find all sorts of invertebrates, miscellaneous insects (of course), solifugids (“sun” or “wind scorpions”) and one time I even found a tarantula (probably a Aphonopelma; I damn near stepped on it while running through the back yard).

As for vertebrates I often found Slender salamanders (Batrachoseps) and the feisty Southern alligator lizard (Elgaria) but never any fence lizards. To find them I had to hike three quarters of a mile or so to an undeveloped area dominated by a rocky hill (a modest pluton locally known to us a “Lionshead”) where they were fairly abundant amongst boulders of decomposing granite.

This is not the case anymore.

I had noticed on previous visits that the fence lizards were around my parents’ yard but today I realized that the place was absolutely crawling with them. I have no idea what has changed in the environment that has led to an expansion of their range, from the hills and undeveloped areas to the middle of the suburbs, but personally I’m glad of it.

At first they played a little hard to get. It was already afternoon and while it wasn’t really hot it was warm so their metabolizes were no doubt running at nearly at mammalian levels. So they would dash for cover before I got too close.

This little one was hiding behind some old window screens at the back of the garage. It had a larger companion who was missing part of its tail, however I couldn’t get a picture of it. Read on»


I was looking through some “old” pictures I had taken and ran across this excellent example of crypsis:

Can you see me?

Photo taken in Joshua Tree National Park (California), six years ago tomorrow (3-12-2006).

Creationists are just buggy about bugs

A few months back Frank Sherwin,  “Senior Science Lecturer” at the Institute for Creation Research, launched an amusing attack on evolution that is nigh on word-salad; this time focusing on insects, and how they are supposedly problematic for evolutionary theory.

As usual it is stated with the confidence and the faux authority that is typical of “creation science” practitioners but when you actually look at it and try to make sense of what is being said it quickly becomes apparent that much of it is really unintelligible nonsense.

Read on»

Up close and personal with mountain gorillas

I shared this on Facebook a while back, thought I’d post it here as welleasy content… Seriously though, if you’re not amazed by this then there is something wrong with you.

I love the part were Daddy silverback pulls the young gorilla away from the funny looking hairless ape. I can almost hear him saying; “stay away from that, you don’t know where its been!” Click here for more on the mountain gorilla (Gorilla beringei).

Symphony of Science – Evolution

Not my cup of tea* musically but fun just the same:

Hat tip to Michael Barton at The Dispersal of Darwin.

*technically no cup of tea is my cup of tea, as I loathe tea.

Darwin’s Pigeons

This seemed apropos:

[Hat tip to the WhyEvolutionIsTrue channel on YouTube.]

Inside Nature’s Giants – Polar bear

This is the latest in the wonderful Inside Nature’s Giants television series (U.K.) and while it unfortunately (at least as far as I’m concerned) spends more time on environmental issues than anatomy, it is still definitely worth watching; so here you go, enjoy:

There’s something fishy about that fish

Institute for Creation Research President Dr. John Morris has taken to recycling; in this case he’s dusted off some nonsense from an article he wrote 3 years ago titled “Evolution’s Biggest Hurdles” (Morris 2008) and repackaged it as “The Biggest Problems for Evolution” (Morris 2011).

As I usually do I started out writing a point by point re-rebuttal to Morris’s new article; even though I already wrote a fairly extensive rebuttal to the earlier version. However, as I was writing, and as it got longer and longer, I realized that I was going to bury the lead way too deep. So, I am dropping most of the rehashing and jump to the new issues I want to address.

First though just a little of the lead in for context:

Morris: Even though the gaps in the fossil record are found between each basic animal type, there are two huge gaps in particular that should be emphasized. The evolutionary distance between single-cell organisms and the vast array of multicellular, highly complex marine invertebrates precludes even rapid evolution.

Oh boy, this is déjà vu all over again.

From earlier context (see below) the “rapid evolution” he is referring to here is supposed to be punctuated equilibrium, however P.E. about apparent, geologically, “rapid” transitions (say a few tens of thousands of years) and concerns species level transitions (like those necessary to evolve horses and zebras from a common ancestor) not multicellular organisms from unicellular ones. Again, I’ll have more on his use of P.E. below.

As for the gap between unicellular and multicellular organisms the (really) short answer is: choanoflagellates (colony forming single celled organisms that are strikingly similar to cells found in sponges called choanocytes). Again, see my earlier post You can tune a piano but you can’t tunicate” for more.

Morris In the supposedly 600-million-year-old layers of rock designated as Cambrian (which contain the first appearance of varied multi-cell life), sponges, clams, trilobites, starfish, etc., are found without the required evolutionary ancestors.

Wrong, wrong, wrong. I covered this before as well.

1) There are fossils of multicellular organism in Precambrian strata (the Ediacaran biota for example).

2) Amongst those Precambrian multicellular organisms are sponges and jellyfish.

3) “Clams” (bivalve mollusks) are known from the Cambrian but only from few tiny extinct types.

4) Starfish or sea stars (Class Asteroidea) fossils do not appear in the fossil record until the Ordovician.

Morris: The gap from marine invertebrates to the vertebrate fish is likewise immense.

Again, Dr. Morris doesn’t want you to know about invertebrate chordates or the evidence for a relationship between chordates and echinoderms. I’ll have more on this in a few moments.

OK, now we get to it:

Morris:  To make matters worse for the evolutionists, fish fossils are also found in Cambrian strata.

If we define the colloquial term “fish” in the usual way (in reference to all aquatic, gill bearing, vertebrates) then yes, a few genera of “fish fossils” have indeed been found in Cambrian strata.

However the word “fish”, is not a scientific term, so the question must be; exactly what sort of “fish” has been found in the Cambrian strata? Dr. Morris does not grace his readers with any further comment on this question; there is however a prominent illustration of a fossil fish that accompanies the article. Here is a screen shot of the page the article appears on:

And here is a larger version of the fish fossil picture:

I think it is fair to say that most people who are not particularly familiar with vertebrate phylogeny and paleontology—including most of Dr. Morris’s readers—might assume when they read in his article that “fish fossils are also found in Cambrian strata” that the large centrally displayed picture of a fossil fish might in fact be one of the Cambrian fish Morris is referring to.

Read on »

The amazing Australian Peacock spider

Isn’t he gorgeous? He’s an Australian peacock spider (Maratus volans) and the photo is by Jürgen Otto. He has a whole gallery of even better photos of this spectacular little arachnid that you’ll want to check out.  However what you really have to see is his video of the dance the males perform to attract the females (you might want to watch it on YouTube for the slightly larger format):

Absolutely wonderful images that demonstrate how apt the common name for these little spiders is. Thank you Jürgen for sharing them.

[Hat tip to Jerry Coyne.]