Hammer Time: Lightning Strikes Thrice (at Least)

All mammals have three small bones in their inner ear that propagate sounds waves in order to allow the animal to hear.  This is a very complicated arrangement of these three bones, and each of them have a different embryological and evolutionary pathway.  Stephen Jay Gould, in an article entitled "An Earful of Jaw" in Natural History (1990), describes the change of each of these bones (all emphasis mine):

But how can something original ever be made?  How can organisms move to a truly novel environment, with needs imposed for functions simply absent before?...

The odyssey of the stapes (stirrup) is extraordinary enough, a tale worthy of the Schilla, Charabdis, and all the whiles of Circe - from gill support to a brace between jaws and braincase to a hearing bone for airborne sound.  Yet the other two bones of the mammalian middle ear... have an even more curious history.  The transition, so improbable in bold words, is beautifully documented in the fossil record and in the embryology of all modern animals.

Quoting C.B. Reichert: "Seldom have we met a case, in any part of animal organization, in which the original form of an early [embryological] condition undergoes such extensive changes as in the earbones of mammals.  We would scarcely believe it... nevertheless, it happens in fact."

Gould continues to ask an important question: why? 

In particular, why should such a transition occur - especially since the single-boned stapedial ear seems to function quite adequately (and, at least in some birds, every bit as well as the three-boned mammalian ear)?

I have always thought that the proposed macro-evolutionary changes of the reptilian jaws to the mammalian inner ear via purely naturalistic processes was implausible.  Because of the complexity of the inner-ear mechanism, it seemed like a just-so story (albeit a fascinating one).  According to this recent article in Science, it just became more so...

Listen up: mammals seem to have evolved the delicate bone structure of the middle ear at least twice. The surprising discovery comes from a fossil, found off the southern coast of Australia, that belongs to an ancestor of the platypus.

Modern mammals are unique among vertebrates for possessing three tiny bones in the middle ear. The malleus, incus and stapes (commonly known as the hammer, anvil and stirrup) work as part of a chain that transmits sound towards the skull. Birds and reptiles have only one bone to perform this function.

Because the mammalian arrangement is so complex, scientists believed that the set-up had evolved on just a single occasion, in an ancestor that gave rise to placental animals (including humans), marsupials and monotremes (such as the duck-billed platypus).

In fact, in a commentary regarding this discovery, Thomas Martin states that the inner ear actually evolved at least three separate times:

The structure of the middle ear is so complex and unique that some researchers consider the separation of the middle ear bones from the mandible to be the strongest synapomorphic (shared derived) characteristic of living mammals. 

No matter how complex the modern mammalian middle ear seems to be, when its distribution is mapped onto the latest mammalian family tree, the middle ear bones appear to have evolved at least three times. 

Not only did this extremely complex group of bones evolve via naturalistic processes once in mammals, it happened independently a number of separate times.  Lightning strikes more than twice.

This discovery was not predicted by evolutionary theory.  Listen to what many researchers are saying regarding this:

Many paleontologists have doubted that such a seemingly complex adaptation could have originated more than once in mammals, but according to the authors of the paper, the evidence of T. trusleri indicates that it did.
"Nothing like that has ever been found before," said Tom Rich, PhD, lead author of the paper and curator of vertebrate paleontology at Museum Victoria in Melbourne, Australia.

And,

Rich and his colleagues had recently unearthed a fossil of Teinolophos trusleri, an ancestor of modern monotremes that lived 115 million years ago. "He said he had some new Teinolophos specimens and when he showed them to me I almost fell off my chair," says Hopson, an author of the study, published this week in Science¹...

This means that natural selection must have driven the same rearrangement in independent groups, after the monotreme split. "Some embryologists had the idea that it might be convergent but nobody really believed this," says palaeontologist Thomas Martin of the Senckenberg Research Institute in Frankfurt, Germany. "I was quite shocked when I heard that such a complex morphological transformation happened twice."

The discovery will compel many experts to rethink their appreciation of mammals' common evolutionary heritage. "Until now it was considered to be one of the most important shared derived characteristics of modern mammals," says Martin

Although it is common to see evolutionists list anatomic similarities between species as homologies and evidence of common descent, this is an example of an anatomic similarity that does not come from common descent.  The anatomic similarities of the inner ear are not homologous, but are complex accidents of nature according to evolution.

Many questions arise.  If one ear bone transmits sound well, why did a more complex arrangement of three evolve multiple times?  Why do we see this arrangement in all mammals, but not in reptiles or birds?  Wouldn't evolution via completely natural processes predict a more random arrangement of inner ear components? 

The evolutionist response is predictable.  Since the conclusion of naturalism has already been accepted a priori, they will simply point to this as exemplifying the wonderful creative power of natural selection.  "Its even better than we predicted!"  Of course, this will be no doubt surrounded by a bunch of ad hominems, mentions of "stupid creationists", and straw man arguments.  We'll have to wait and see.