Mammal to reptile evolution...

Question

According to my book, the theory is that reptiles eventually evolved into mammals. However, reptiles have several bones in the jaw, whereas mammals only have one. Reptiles have one bone for the 'ear', while mammals have three. It says that experts believe the bones from the reptiles jaw migrated to the ear.

My questions are, how did the reptiles' ears and mouth function during the process? How did the hear and eat?

Also, why have no fossils of organisms been found with the transition taking place i.e. with say two jaw bones and two ear bones?

Answer 1

Let me guess, your book is "Evolution? The Fossils Say No!" by Duane Gish. If so, you've been duped, this book is full of lies.

"We also have an exquisitely complete series of fossils for the reptile-mammal intermediates, ranging from the pelycosauria, therapsida, cynodonta, up to primitive mammalia..."

http://www.talkorigins.org/faqs/comdesc/...

Evolution of the mammalian cranio-mandibular joint and the definitive mammalian middle ear through the cynodont-mammal transition.

http://www.nature.com/nature/journal/v45...

From Transformation and diversification in early mammal evolution:

http://www.talkorigins.org/faqs/comdesc/...

Answer 2

As previousl mentioned by others your "logic " is like a sieve.  By the way Duane Gish and Michael Behy are both card carrying mebers of the Cration Science Institute whose # 1 tenet is belief in the inerrancy of the Bible...that the Bible is an authentic ---perfect historical account ( none of these statements with any proof whatsoever ). Their attempts at undermining the theory of evolution were definitively trounced in the Dover Decision. It is strange that the  world's most prestigious science organization National Academy of Science would support a theory that creationists so dispise and maintain is untrue..   Hmm methinks that cerationists ought to spend a little more time with authentic books by real experts of evolution and molecular biology and paleontology, and anthropology that with a book written by men in an age when they thought the earth was flat, the center of the Universe, that demons caused disease, etc etc .....hardly the stuff for formulating real scientfic inquiry

Answer 3

Looking at the position of the bones in question it seems like they don't really 'migrate' so much as they change function (first ref below).

I did find some interesting references for some of your questions.  From my reading of it reptiles were more sensitive to ground vibrations, and did not hear the higher frequencies that mammals do.  And they talk in these articles about a transition fossil (also below).

There is also a Wiki mention of the genes responsible for the formation of these bones (see below).  They are homeobox genes, things responsible for body pattern formation.  As long as the mutations that allowed these changes to occur still allowed for eating and hearing, then there is very little selective pressure that would suppress them.  And there would be benefit from this increase in perception of higher frequencies that would be a factor for positive selection.

Why we don't see the transitions of everything is just usually a function of the fact that it all happened a long time ago, that the fossils are buried and incomplete and stuff like that.  

Answer 4

Absence of evidence is not evidence of absence.  Also creationists have a nasty habit of grossly under-representing the detail of the fossil record.

Now that said.  First of all the three mammalian ear bones you refer to (the ossicles) are not required for the sense of sound, they simply amplify sound by connecting an eardrum to a choclea.  So the sense of sound predated the ossicles and when the ossicles "moved" they just provided another source of variation on which selection could act.  As for how did they eat?  These are the smallest bones in the body, I find it hard to imagine there loss in a jaw would be debilitating.

All of this is besides to point,  why do you focus on trivial anecdotes when you ignore the big picture.  Nothing in biology makes sense except in the light of evolution

Answer 5

Your observations are very accurate!

There ARE no transitory fossils.  In fact, evolution remains a THEORY.

You do know the difference between THEORY and FACTS, don't you?

A THEORY is a GUESS at how something happened.  Scientists see that something HAS happened, then they make a guess as to HOW it happened.  They then spend a great deal of time, effort, and money to prove or disprove their theory.  

For example, there is a lot of talk about Black Holes right now -- but nobody has ever actually seen one!  Scientitst make a THEORY that there is one at the center of each galaxy, but no one has yet been able to PROVE that is true.  So Black Holes ramin as a THEORY -- a guess -- until such time as some proof comes in.

If they find evidence that their theory was correct, then it becomes FACTS. If they find out that their theory was wrong, then they invent a new theory and start over.

The problem with evolution is that the "proof" of the theory has never been found.  As you point out, where are the transitry fossil?  How could an animal function that had jaw bones in its ears?  

It just really doesn't make sense.

Answer 6

I can't improve on KTDyke's outstanding answer, other than to point out why this is exactly why reading Creationist literature is so misleading.   Their arguments are based on *unforgivable* oversimplification of the science.  

And of course, answers like Gary B's reveal what happens when you are a bit too willing to accept the mere asking of a question as evidence that the 'evolutionists' have no answer.

Also, statements like "A THEORY is a GUESS at how something happened." reveal that Gary B doesn't even have a passing High School understanding of science (hint: that is NOT what a theory is in science) ... and yet feels he knows enough to disagree with the overwhelming consensus of the world's scientific community.  

That is the problem with Creationism.  You only have to scratch the surface to reveal that Creationism is entirely constructed on scientific illiteracy.   The authors of Creationist literature absolutely *DEPEND* on the scientific illiteracy of their audience.    These Creationist sites are not only lying to you ... they are insulting your intelligence.

Answer 7

<<According to my book, the theory is that reptiles eventually evolved into mammals. However, reptiles have several bones in the jaw, whereas mammals only have one. Reptiles have one bone for the 'ear', while mammals have three. It says that experts believe the bones from the reptiles jaw migrated to the ear>>

The part of that I don't personally like is terming the ancestors of mammals reptiles.  They were actually synapsids.  The last common ancestor with reptiles lived, at the latest, around 315 million years ago.  Nevertheless, non-mammalian synapsids (and early mammals) did only have a single hearing ossicle.

<<My questions are, how did the reptiles' ears and mouth function during the process? How did the hear and eat?>>

They ate using their jaws, and heard using their ears supported by several of the jaw bones.  At least, they did in derived synapsids called cynodonts (including early mammals).

<<Also, why have no fossils of organisms been found with the transition taking place i.e. with say two jaw bones and two ear bones?>>

Both those jaw bones were already operating for hearing in cynodonts.  They moved as a unit, not individually, so there never were two middle ear ossicles.  Transitional fossils have been found, and that's how come I can tell you this.  A particularly splendid example is an early mammal called /Castorocauda/.  That one manages to preserve both those gonnabe middle ear ossicles still on its jaw.  The joint had become so weak, that it probably only operated for hearing by that stage.

Update

<<There ARE no transitory fossils. In fact, evolution remains a THEORY.>>

I've just mentioned one by name.  Please desist from writing untrue statements in public.  It's a terrible example for others.  Tell any lies you like in the privacy of your own home, but not in public forums.

Update 2

<<Looking at the position of the bones in question it seems like they don't really 'migrate' so much as they change function (first ref below).>>

They migrated after changing function, although not all that far.  The mammalian jaw joint, the dentary-squamosal, developed alongside the original non-mammalian one, the articular-quadrate.  That started occurring in non-mammalian cynodonts.  Both joints were still in place in early mammals, although the mammalian one was dominant (eg. /Morganucodon/).  With somewhat more derived mammals, docodonts, the jaw function of the original joint ceased.  After then, the whole unit of bones eventually migrated from the jaw to the inner ear, and precisely that still occurs in the embryological stages of mammals.  It's not all that far in terms of distance, and the delivery service is provided by a thing called the Meckelian cartilage.  That's what formed your original lower jaw before, as an embryo, you replaced it with a bone jaw.

A driving force suspected of powering this migration is the expansion of the braincase, but this possibility has its critics as well.

In living mammals, apart from a couple of tiny ossified bits, the Meckelian cartilage fades away and is resorbed.  That wasn't the case in some earlier mammals.  Although soft tissue, that Meckelian cartilage has been found in a fossilized state (eg. /Repenomamus/).  Its front is attached to the jaw while its rear happened to land bang in the middle ear.

Does anybody else want to write about "a total lack of transitional fossils"?

Answer 8

Jaw bones became ear bones. Reptiles heard pretty well underwater, and I think they do have transitional forms.