The jaw of Teinolophos trusleri catches the ear bones in the act of separating from the jaw.
Posted on 02/11/2005 6:49:09 AM PST by PatrickHenry
Triple bone structure arose independently in platypus and humans.
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).
All this changed when James Hopson, a vertebrate palaeontologist at University of Chicago, Illinois, took a trip to Australia. There he met a team of researchers including Thomas Rich of Museum Victoria in Melbourne.
The jaw of Teinolophos trusleri catches the ear bones in the act of separating from the jaw.
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 inScience [Rich T. H., et al. Science 307, 910 - 914 (2005)].
Hammer time
Palaeontologists believe that the middle-ear bones of modern mammals once belonged to the jawbone and later separated to adopt their present location. This is supported by the fact that the middle ear's bones associate with the jaw in the early development of modern mammalian embryos.
What makes theTeinolophos specimen surprising is a large groove in its adult jawbone, which indicates that the smaller bones had not yet detached.
Teinolophos lived after monotremes split from the placental and marsupial mammalian groups. Its jawbone structure, along with its place in the evolutionary tree, hints that a common ancestor to all these mammals lacked the special three-bone ear structure.
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.
Hmmm. Did I mention the Bible?
This is the classic response. Rather than freely inquiring into the apparent origin of life, evolutionists set up a false choice between the Genesis account and evolution. Just because it's not black, doesn't mean it's white. Could be orange too.
Evolved twice. It happens quite a bit. That's why bats and birds both have wings, despite being not particularly closely related - convergent evolution.
Do people really not understand that evolution involves random mutations and then the death of all non-mutated individuals and their offspring?
LOL.
"Agree. Evolutionists have to deal with many stubborn facts. Such as the predominance of sexual reproduction. How would a successfully mutated individual advantage its offspring by mating with a non-mutated individual and diluting or eliminating its genetic advantage in that offspring?
I was thinking the other day about all of the distinct breeds of dogs that were -- yes -- designed by human intervention. What do you think would happen if all humans were suddenly removed and those dogs ran wild and interbred? It is most likely that you would soon end up with the conglomerated brown/gray mutt that you see hanging around in poor third world countries. In other words, the dogs that may have developed some survival "advantage" over the others would nonetheless copulate with the first hot bitch -- be it chihuahua or doberman -- that they found. That's what undirected randomness involves."
As for sexual reproduction, I suggest you use your God-given brain and think. Every October I watch the male elk gather 40-50 cows. Nest year, there will be 40-50 young elk with his genes. If he had to do it asexually, he might be able to crank out one young elk every two years, vs 80-100 sexually. Now do you see? Besides, incase you've forgotten or never had the opportunity -sex is fun 8^).
As for the rest of your post. Hmmm.. I suggest you go to you library and get a Biology Book and read it. It's clear that you learned all you know about Biology in Government Schools. Just because you have a computer, does not give you a license to spew blather.
God created adaptation, which is called evolution these days. The reason we are all so similar is because of the DESIGNER, not the design.
Why is evolution contrary to God? He created all.
My biggest problem with natural selection as a process to explain speciation is the lack of mutagens. If the genetic dice are being re-rolled every time another individual animal is conceived, thus giving rise to new and potentially useful structures that promote that individual's survival, then...well...where are the mutations, and what's driving the process?
If you roll a six-sided die and get a seven, it's for a reason. I'm open-minded as to what the reason might be, but I am convinced that there must be one. Random mutation alone doesn't seem to me regular enough to result in speciation, particularly when random mutation usually results in fatal defects in individuals.
You couldn't be more right. Which is why one of the key requirements for significant evolution in a species is population isolation. The larger the population pool, the smaller the potential for change.
I should elaborate that that's one of the reasons that large landmasses (Eurasia for instance) have relatively little biological diversity compared to isolated islands (Galapagos, New Guinea).
I came here for a thread about a sawed-off, pretty boy, Greek aid to ex Pres Clintoon and all I got was a thread about a damned bottom feeding rodent.
same thing I guess.
Platypus fact. It is the only venomous mammal.
He was lazy and left unnecessary and/or poorly designed components in, just because that's what the template was set for? Remind me again why He didn't both to design a spinal column better suited to bipedalism?
I wanted to say neener, neener, neener, but I thought it would be childish in the midst of a serious discussion.
How about a woman scorned?
Did you THINK up those arguments for yourself?
>Its jawbone structure, along with its place in the evolutionary tree, hints that a common ancestor to all these mammals lacked the special three-bone ear structure.
This means that natural selection must [be a load of crap...]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[or NEVER]."
The discovery will compel many experts to rethink their [bogus concepts] 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.<
???
"When evolution is outlawed, only outlaws will evolve?"
"When ID is outlawed, only outlaws will design intelligently?"
"When creation is outlawed, only outlaws will (pro)create?"
More details, please...?
Where'd you get that photo? That's FUNNY!
I will take up your illustration rather than respond to your ad hominem attack, which seems pretty pointless since you don't know me.
First, for your illustration to have much impact at all, the genetic mutation has to be in a (randy dominant) male, has to be absolutely random, has to be beneficial (most aren't by the way), has to be so beneficial that it confers a significant competitive advantage on its offspring, and must be expressed in a dominant allele that is not erased or corrected by the female's allele (most mutations are recessive). Then any offspring with the beneficial mutation must ultimately be exposed to all of the other elk from all of the other nearby herds where more dilution will occur. And all of the non-mutated elk elsewhere must die off -- otherwise the species hasn't evolved at all -- you'd simply have dark brown elk in one place and light brown elk in others. Without this die-off, all would adapted to their surroundings and capable of interbreeding at any time. And if your mutated elk can make it through all of this -- not to mention periodic, localized droughts and die-offs, you have, after hundreds or thousands of generations, succeeded in making ONE small change to the species.
Now tell me how a super dog emerges from my scenario?
Interesting! I've never heard that one before. I've spoken to people with Ph.D's about the spine and the structure of the spinal column and they have said that the design and robustness of it is remarkable.
Oh, it is remarkable. Just not well-designed for upright walking. If you don't believe me, just ask any chiropractor how he/she makes a living.
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