Archaeopteryx, cladistics, ghost taxa, and anti-evolution movements

Archaeopteryx is perhaps the best known “transitional fossil” in the sense of public recognition.  First discovered in Germany in 1861, 2 years after the publication of the first edition of Darwin’s Origin of Species, it has been hailed as a transitional phase between reptiles and birds ever sense.  Darwin himself was aware of the existence of Archaeopteryx, and addressed this fossil in later editions of the Origin.  Consider the following passage from the 6th edition of the book:

“[A]nd still more recently, that strange bird, the Archeopteryx [sic], with a long lizard-like tail, bearing a pair of feathers on each joint, and with its wings furnished with two free claws, has been discovered in the oolitic slates of Solenhofen.  Hardly any recent disc overy shows more forcibly than this , how little we as yet know of the former inhabitants of the world.” (Darwin 1859:444  see 6th edition here).

While Darwin at least mentions the existence of Archaeopteryx here, it is in a letter from paleontologist Hugh Falconer to Charles Darwin, from Jan. 3, 1863, where we begin to see the true significance of the find:

You were never more missed—at any rate by me—for there has been this grand Darwinian case of the Archaeopteryx for you and me to have a long jaw about…You are not to put your faith in the slip-shod and hasty accoutn of it given to the Royal Society.  It is a much more astounding creature—than has entered into the conception of the describer” (Falconer, 1863 in Correspondences vol. 11 p.5)

Falconer’s statements here tell us a number of things.  First, that he saw Archaeopteryx as a valid “transitional” fossil, or as evidence in favor of evolutionary theory.  Second, it is obvious here that Falconer had a large amount of respect for Charles Darwin as a scientist.  It is worth noting here that Falconer discovered stasis in the fossil record as a valid trend over a century before Eldredge and Gould’s 1972 work on Punctuated Equilibria, thus rendering Eldredge and Gould as a re-discovery, rather than a discovery, of stasis.  But I digress. 

Moving back to a discussion of Archaeopteryx, the genus was held as a transition between lagosuchids and birds for the first half of the 20th century.  This was largely due to a gappy lagosuchid and dinosaurian fossil record; upon more fossil discoveries, the Lagosuchid line was shown to be  too specialized to be ancestors of birds.  In fact, largely as a result of the work of John Ostrom on Deinonychus and Archaeopteryx, dinosaurs were suggested as the ancestors of birds (for more info on this, see Bakker 1986: 298-322).  With the discovery  of more fossils, especially feathered dinosaurs from China, the dinosaur-bird connection has become well-accepted among paleontologists (for more info, click here).

So why are dinosaurs accepted as bird ancestors by scientists today?  As early as the latter half of the 19th Century, TH Huxley noted similarities between dinosaurs and birds.  However, to fully appreciate the modern state of Archaeopteryx, one must look at recent publications.  While there is some debate as to the exact place of birds within the classification of Theropods (bipedal, often predatory, dinosaurs such as Tyrannosaurus Rex), birds are almost universally accepted among paleontologists as a form of derived theropod, generally within the maniraptorian segment of the group (see Benton 1992 p. 22). Looking specifically at Archaeopteryx, let’s consider some of the traits that suggest that birds evolved from dinosaurs.  The skeleton of Archaeopteryx is so similar to dinosaurs that the first specimen discovered was initially mistaken for a Compsognathus (a small type of theropod).  Archaeopteryx, as well as other theropods and birds, had a relatively unique mesotarsal joint (a part of the ankle), a half-moon shaped bone in the wrist (the semilunate carpal), gastralia, an s-shaped curve in the neck, and feathers.  Some more dinosaurian features of Archaeopteryx include conical teeth (similar to those of other early birds such as Hesperornis and Icthyornis), claws very similar in structure to those of dinosaurs such as Deinonychus, and a long bony tail (for more discussion, see Prothero 2007 p. 260). These similarities, among others (such as similarities in hip structure), suggest that birds did, in fact, evolve from dinosaurs.

 However, Archaeopteryx’s status as a “transitional fossil” is often attacked by anti-evolutionists. One of the most popular approaches to Archaeopteryx from this angle is to denigrate Archaeopteryx as a “mosiac form”, and compare it to the platypus (see Johnson1993:80-81).  This approach assumes that the shared characteristics between Dinosaurs, Birds, and Archaeopteryx are of little consequence, just like the bill of a platypus (after all, a platypus has a bill and lays eggs, but nobody calls it a bird!).  However, this approach showcases a large-scale misunderstanding of how paleontology and comparative anatomy work.  Archaeopteryx is not considered a “transitional form” solely because it has some bird-like features and some dinosaur-like features.  It is significant because some of its features are shared ONLY by Theropod dinosaurs and Birds.  A cladistics-based approach to Archaeopteryx will place Archaeopteryx between other “birds” and “dinosaurs” as a “transitional form” (for more on cladistics, click here). This is due to the fact that many features are shared only by Archaeopteryx, Theropods, and other birds, not because Archaeopteryx just “shares some charisteristics” with birds and dinosaurs.  Anti-evolutionists (either ID advocates or Creationists) are fond of using this “mosiac form” approach to fossil proofs of evolution, even though (as demonstrated) it illustrates a misunderstanding of paleontology and cladistics. 

One other objection often raised to the status of Archaeopteryx is the argument that since the dinosaurs that are claimed to be Archaeopteryx’s closest relatives were contemporaries of Archaeopteryx in the Jurassic period, Archaeopteryx cannot be a valid “transitional form”.   However, this argument is also weak.  Using the concept of ghost taxa, or taxa inferred in a cladistic tree from unique shared characteristics, scientists can infer the characteristics of “transitional forms” between Archaeopteryx and the dinosaurs it evolved from, for example.  While this approach assumes the validity of evolutionary theory, this is not a problem, due to the fact that evolutionary theory is uniformly accepted by biologists and paleontologists.  Biologists see natural selection operating on a daily basis, and paleontologists continuously find an ordered, linear sequence within the fossil record.  Combining these two lines of evidence (among many others), one can infer that evolution does, in fact, work.  Therefore, the assumption of evolution as a scientific fact does not present a serious problem.

If Archaeopteryx’s status as a “transitional fossil” is so well-accepted by scientists (note that by saying Archaeopteryx is a traqnsitional form, I am not saying that it necessarily evolved into birds, but rather that it showcases features unique to birds and dinosaurs, which illustrates that dinosaur-bird evolution has taken place, either through Archaeopteryx or some other closely related group of early birds), then why are people still trying to destroy it’s status?  Archaeopteryx is not the problem here.  Evolution itself isn’t even necessarily the problem.  The problem is often that Archaeopteryx, evolution, and a 4.6 billion-year-old earth are seen, at least by some, to threaten the percieved “special place” of humanity in nature. This conflict is the root of the percieved conflict between science and religion.  What is at stake here, from the perspective of Creationists especially, is not science, but rather humanity’s special place, elevated above the rest of the natural world.

Works Cited:

Bakker, RT.  The Dinosaur Heresies: New Theories Unlocking the Mystery of the Dinosaurs and Their Extinction. Citadel Press Books, New York, 1986

Benton, MJ. Origin and Interrelationships of Dinosaurs, in The Dinosauria, edited by DB Weishampel, P. Dodson, and H. Osmolska.  University of California Press, Berkeley, 1992.  p. 11-30.

Darwin, C.  The Origin of Species. 6th edition, reprinted by Castle Books, Edison, 2004. First edition originally published 1859.

Falconer, H. letter of Jan. 3, 1863 to Charles Darwin.  In The Correspondence of Charles Darwin Vol. 11, edited by F. Furkhardt, DM Porter, SA Dean, JR Tophan, and S. Wilmot.  Cambridge University Press, Cambridge, 1999

Johnson, PE.  Darwin on Trial.InterVarsity Press, Downers Grove, 1993

Prothero, DR.  Evolution: What the Fossils Say and Why it Matters. Columbia University Press, New York, 2007.

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Explore posts in the same categories: 1800s, evolution, geology, history of science, Science and Pseudoscience

5 Comments on “Archaeopteryx, cladistics, ghost taxa, and anti-evolution movements”

  1. Chris Says:

    You will find all the answers raised in an incredible book that has just been published called The Darwin Delusion. It has changed the way I think and I urge you to visit http://www.thedarwindelusion.com

    • darwinaia Says:

      I made sure to take some time to go through some of the stuff on the site you linked. Unfortunately, the page reminds me of pretty much all anti-evolution texts; imply that there are things that evolution cannot explain, claim so-called “negative” evidence for evolution as positive evidence for alternate model, and throw in some allusions to how ingrained evolution is in our culture, and also claim that Darwin is seen as a god. It just seems like the same tired old anti-evolution arguments to me. Interesting link though.

  2. chriscolose Says:

    Buy another book, maybe a science one.

  3. johnG Says:

    Very nice post. Thanks especially for the link on cladistics, a topic I need to catch up on, which is also an invitation for you to delve into the topic.

    thanks again for a delightful read.

    jg

    • darwinaia Says:

      Thanks. I’ll have to work something out on cladistics in my next couple of posts. Right now I’m working on one on Kitzmiller v. Dover and another one as a refutation to the idea that Darwin was some sort of hardcore racist (while he was racist by today’s standards, of course, any claim that he was a racist has to be considered against his period, not ours. By Victorian standards, he was quite moderate). I’ll have to add one on cladistics to my list.


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