Researchers: Eardrum evolved independently in mammals and reptiles/birds

_{Denyse O'Leary

May 14, 2015

Convergent evolution, News}

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Researchers at the RIKEN Evolutionary Morphology Laboratory and the University of Tokyo in Japan have determined that the eardrum evolved independently in mammals and diapsids — the taxonomic group that includes reptiles and birds. Published in Nature Communications, the work shows that the mammalian eardrum depends on lower jaw formation, while that of diapsids develops from the upper jaw. Significantly, the researchers used techniques borrowed from developmental biology to answer a question that has intrigued paleontologists for years.

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The Parts List for Hearing Want to hear what goes on when you hear sounds? Hair cells wave in the fluid, responding to specific frequencies, and hundreds of proteins go into action. Talk about splitting hairs. Harvard Medical School begins a press release with some gee-whiz facts about the hair cells involved in hearing:
For balance, five separate patches of hair cells sense movement and tell the brain where the head is in space while translating the pull of gravity.

For hearing, a five cell-wide ribbon of 16,000 hair cells spirals inside the cochlea, the snail-shaped structure where hair cells vibrate in response to sound waves. Every cycle of sound waves sends microscopic cilia on the tips of these cells back and forth, riding a trampoline of cells suspended between two fluid-filled spaces.

The movement opens pores in the cells, allowing electrical current to flow inside. This conversion of mechanical to electrical signals sends nerve impulses to the brain, which then “hears” the sound.
http://crev.info/2015/05/parts-list-for-hearing/#sthash.iue6HCMB.dpuf For a picture of what all this looks like, check out this diagram: https://hms.harvard.edu/sites/default/files/assets/News/2015/images/May/HairCells-GFP-Corey.giftjguy_{May 16, 2015
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"It is amazing. Hearing, apparently, was necessary because there are soundwaves out there that organisms needed to listen to. Of course!" And radio stations everywhere are rejoicing!OldArmy94_{May 15, 2015
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Querius
Sciencemag.org provides clues on how these animals coped during the long evolutionary process by way of how whales coped with moving from land to water: When whales moved from land to water, they had to make two major changes to ensure that they kept hearing: They enlarged and rearranged the ossicles to transmit underwater sounds. And, in order to retain directional hearing, they had to prevent sounds from passing through the whole skull to the ear.
LOL - that is brilliant. They enlarged and rearranged the ossicles. So, then they could transmit sounds underwater. Of course! :-)Silver Asiatic_{May 15, 2015
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It is amazing. Hearing, apparently, was necessary because there are soundwaves out there that organisms needed to listen to. Of course! Nothing needed teleportation or x-ray vision though. Even humans didn't need their own vision to stay accurate through the course of one lifetime. There's a selective advantage to near-sightedness and glaucoma - obviously. :-)Silver Asiatic_{May 15, 2015
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:-/ If birds and mammals evolved eardrums independently, then there was a time when birds and mammals each did not possess eardrums. However, snakes possess cochleas and inner ear bones that are sensitive to vibrations in their jaws, so the MRCA for birds and mammals are presumed to rely on vibrations through their jaws, as well as early mammals and birds as they pressed their heads onto the ground when they wanted to hear. As science20.com explains it:
The evolution of the eardrum and the middle ear is what has allowed mammals, reptiles, and birds to hear through the air.
According to the article,
Chief Scientist Shigeru Kuratani notes that, "convergent evolution can often result in structures that resemble each other so much that they appear to be homologous. But, developmental analyses can often reveal their different origins."
So, the convergent evolution of virtually homologous features is common, but can only be revealed by developmental analysis, which is apparently a handy method for repositioning the limbs in the tree of life! Sciencemag.org provides clues on how these animals coped during the long evolutionary process by way of how whales coped with moving from land to water:
When whales moved from land to water, they had to make two major changes to ensure that they kept hearing: They enlarged and rearranged the ossicles to transmit underwater sounds. And, in order to retain directional hearing, they had to prevent sounds from passing through the whole skull to the ear.
So if these clever whales could make the additional changes using only their flippers and perhaps large feet, then one can assume birds, being far more dexterous could easily follow suit! Simply amazing, isn't it? ;-) -QQuerius_{May 14, 2015
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Its easy to invoke evolution bringing like results a thousand times if it could do such a complex thing the one time. Its a better idea there is a common blueprint in nature and biology has it as needed.Robert Byers_{May 14, 2015
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Deaf lol. Are Hellen Keller jokes allowed on UD? Ok, what is the difference between the MRCA and Helen Keller? Helen Keller had mammary glands. Bwahaha. Ha. http://www.yuksrus.com/celebs_helen_keller.htmlppolish_{May 14, 2015
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Does this mean that these Darwinian researchers believe the MRCA of birds and mammals was deaf? Just asking. -QQuerius_{May 14, 2015
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Link probably fixed now. Odd one.News_{May 14, 2015
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Your link did not work for me News. Here is another link with the story:
Eardrum evolved independently in mammals, reptiles and birds - 04/22/2015 Excerpt: Researchers,, have determined that the eardrum evolved independently in mammals and diapsids—the taxonomic group that includes reptiles and birds.,, the work shows that the mammalian eardrum depends on lower jaw formation, while that of diapsids develops from the upper jaw. Significantly, the researchers used techniques borrowed from developmental biology to answer a question that has intrigued paleontologists for years.,, They noted that in mammals, the eardrum attaches to the tympanic ring—a bone derived from the lower jaw, but that in diapsids it attaches to the quadrate—an upper jawbone.,, While scientists still do not know how or why the primary jaw junction shifted upwards in mammals, the study shows that the middle ear developed after this shift and must therefore have occurred independently after mammal and diapsid lineages diverged from their common ancestor. http://www.sciguru.org/newsitem/18946/eardrum-evolved-independently-mammals-reptiles-and-birds
Moreover, this finding is important because Neo-Darwinists have used a fictitious fossil series leading from reptile jaw bones to mammalian inner ear bones, for years, to argue for the supposed evolution of mammals from some reptilian ancestor. That particular Darwinian fairy tale is gone over at the 31:49 minute mark of this following video (you have to skip over 31:49 minutes of a ‘brief’ description of the amazing engineering and design of the ear to get to the 'just so story' offered by evolutionists for how that amazing sophistication in the ear 'randomly' came about).
The Hearing Ear by Dr. David Menton - video https://www.youtube.com/watch?v=HPiXlJ3eIwo&feature=youtu.be&t=1863
bornagain77_{May 14, 2015
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