Posted on 01/18/2006 6:10:34 PM PST by PatrickHenry
Our ears could have started evolutionary life as a tube for breathing, say scientists, after examining the ancestral structure in a 370-million-year-old fossil fish.
Evolutionary biologists are intrigued by how complicated sensory organs evolved from structures that may have had completely different uses in ancestral creatures. The bony structures in ancient fish, which at some point turned into ears, for example, appear to have had mainly a structural function, bracing the cheek and holding up the jaw. How exactly they made the transition to their role in hearing has proved a bit of a mystery.
The ear is a relatively easy organ to study. Its evolving bones have been preserved as fossils, whereas the soft tissues of other specialized features, such as eyes and noses, have long decayed.
So Martin Brazeau and Per Ahlberg of Uppsala University in Sweden decided to take a close look at the ear-like features of an ancient, metre-long monster from the Latvian Natural History Museum in Riga. Panderichthys was a fish, but is thought to be closely related to the earliest four-limbed tetrapods that eventually climbed on to land and gave rise to modern vertebrates.
The researchers examined Panderichthys and found that the bony structures in its head combine features of fish and tetrapods, capturing a snapshot of evolution in action. "It's neat to see that transition," says Hans Thewissen who studies the evolution of the ear and other organs at Northeastern Ohio Universities College of Medicine, Rootstown.
Half-way house
Ancient fish have a narrow channel from the roof of the skull into the mouth, known as a spiracle, which is bounded by a long bone known as the hyomandibula that braces the cheek. In tetrapods, the equivalent bone is stubbier, a step towards the stirrup-like stapes bone that helps to transmit sound waves into our skulls.
The team found that Panderichthys has a wide, straight spiracle rather than a narrow one, and a shortened hyomandibula. They report their findings in Nature1.
Some have previously speculated that our ancient ears may have had a role in breathing.
On the basis of this new fossil evidence, the team speculates that the widened spiracle may have served Panderichthys much like the breathing holes used by modern-day sharks and rays. These allow the fish to inhale water over their gills while lying on the seabed, and avoid gulping in grit through the mouth.
| The demonstration of an organ evolving provides tangible evidence against the idea, put forward by some proponents of creationism, that sensory organs are so intricate that they must have been designed by a higher being. Brazeau says: "It's a slap in the face to that kind of thinking." |
In case you haven't noticed, this is an online forum of debate. If you get queasy, have a nice glass of Sprite.
I can't help thinking that breathing through your ears would be an advantage in oral sex -- and wondering whether that's a plus for reproduction or a minus? ;^)
Who told whom to shut up?
Who told you that this article reported that the ears were once used for the sense of smell? I asked you that once before, because you asserted that. If you're going to participate then do it responsibly.
Well, perhaps you haven't evolved either a sense of irony or humor. But you generally smell where you breathe (or taste).
Likewise reproduction. It evidently has to have been "programmed" in from the beginning, or there'd be no "evolution" to discuss.
Really? I have asserted that they are more easily caughtbecause their deceptions are more obviously deadly. Whereas if a cosmologist waves his hands and murmurs soothingly about "billions and billions of years"--who can say him nay?. That's the thing about stats and their obfuscatory nature--they often reveal an accompanying condition rather than the fact they seem to reveal.
Thanks. And for some reason all of them seem to post their ignorant rants to me.
Ignore them.
This is incorrect. Fish in general don't have bones in their inner ear. Because fish live in water, and have a body density close to that of water, sound vibrations travel into and through their bodies easily, and they don't need a mechanism to transmit sound from an external opening (like the ears of land animals) to the inner ear.
They have rather the opposite problem -- the sound would pass right through their bodies without much of it being "captured" to be "heard". So they need something of greater or lesser density than water to "register" the sound on. Most fish use the skull itself (pretty much as a whole), as well as mineralized pellets inside the inner ear canals known as otoliths, which vibrate as the sound passes through the inner ear (the *inside* of the inner ear) and the wiggling of these otoliths directly stimulate the nerve endings in the inner ear.
So no, fish don't have "three inner ear bones".
Some families of fish, such as herrings, anchovies, squirrelfish, and others have a swim bladder which extends to near the inner ears and also helps to transmit sound vibrations to the ears (since the swim bladder, filled with air, is also of different density than the surrounding water.
The Ostariophysi take this system to extreme, and actually use four vertebrae as a sound-carrying channel to carry the sound more efficiently from the swim bladder tothe inner ears.
The first fish which had adaptations that allowed them to travel out of the water and onto land would have had ears which worked well in water, but very poorly in air. So there was strong evolutionary pressure to modify existing structures to transmit sound from the outside air (near the skin, obviously) into the location of the inner ear. This is where the amphibian/reptile system of using a modified bone (the hyomandibular in fish) as a sound transmission rod (the stapes bone in amphibians and their descendants). Also the tympanic membrane developed as a specialized region of skin which was thin and vibrated easily when sound was present (as can still be seen on frogs, which have this "surface eardrum" visible behind their eyes).
The reptilian ear was a refinement of this system, with a more specialized stapes and the tympanum sunken below the surface (in some reptile families).
Finally there's the reptile -> mammal transition, in which two of the small jawbones in reptiles migrated to join the stapes to make the classic mammalian inner ear (as documented here).
My remarks were in response to your false and unwarranted attacks upon my profession.
And you trust the PEERS? I'm glad America moved beyond the peerage. I don't need barons and squires and such-- Fraud is rife in scientific academia. The stakes are high--prestige, money, status, money, careers, money, tenure, money.
You began the ad hominem attack on me and my fellow scientists--it wasn't germaine to this thread. If you don't like my replies, then stop with these personal attacks.
I spend a lot of time in academia actually. I don't agree with what you are saying, frankly. It does sound a bit hysterical.
Are you serious?
Did you even READ the article? This krap passes as science these days?
Let's post the story again, but this time let's highlight the revealing keywords of darwinian evolutionary "science."
Our ears could have started evolutionary life as a tube for breathing, say scientists, after examining the ancestral structure in a 370-million-year-old fossil fish.
Evolutionary biologists are intrigued by how complicated sensory organs evolved from structures that may have had completely different uses in ancestral creatures. The bony structures in ancient fish, which at some point turned into ears, for example, appear to have had mainly a structural function, bracing the cheek and holding up the jaw. How exactly they made the transition to their role in hearing has proved a bit of a mystery.
The ear is a relatively easy organ to study. Its evolving bones have been preserved as fossils, whereas the soft tissues of other specialized features, such as eyes and noses, have long decayed.
So Martin Brazeau and Per Ahlberg of Uppsala University in Sweden decided to take a close look at the ear-like features of an ancient, metre-long monster from the Latvian Natural History Museum in Riga. Panderichthys was a fish, but is thought to be closely related to the earliest four-limbed tetrapods that eventually climbed on to land and gave rise to modern vertebrates.
The researchers examined Panderichthys and found that the bony structures in its head combine features of fish and tetrapods, capturing a snapshot of evolution in action. "It's neat to see that transition," says Hans Thewissen who studies the evolution of the ear and other organs at Northeastern Ohio Universities College of Medicine, Rootstown.
Half-way house
Ancient fish have a narrow channel from the roof of the skull into the mouth, known as a spiracle, which is bounded by a long bone known as the hyomandibula that braces the cheek. In tetrapods, the equivalent bone is stubbier, a step towards the stirrup-like stapes bone that helps to transmit sound waves into our skulls.
The team found that Panderichthys has a wide, straight spiracle rather than a narrow one, and a shortened hyomandibula. They report their findings in Nature1.
Some have previously speculated that our ancient ears may have had a role in breathing.
On the basis of this new fossil evidence, the team speculates that the widened spiracle may have served Panderichthys much like the breathing holes used by modern-day sharks and rays. These allow the fish to inhale water over their gills while lying on the seabed, and avoid gulping in grit through the mouth.
You guys SURE SEEM SURE of yourself. Not.
To be honest it was rather embarrassing. I felt like I'd just inadvertently read an entry from somebody's diary, and wished that I hadn't. And you haven't actually 'disagreed' with me, per se. You do not appear to be debating; it looks more like venting.
"Fellow" scientists?
Who cares? He can murmur all he wants, but he won't be published unless he makes and evidence based claim.
Who cares? He can murmur all he wants, but he won't be published unless he makes an evidence based claim.
Carry on!
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