HappyCetacean
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This seems to sum up Stripe very well.
Real Science Friday Trochlea Challenge
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This seems to sum up Stripe very well.
Okay, if no-one has addressed the trochlea directly, I got my information primarily from the Richard Dawkins forum where it was discussed last Dec. and I owe my response entirely to one Devlo whoever he are she is and then did some googling on my own to verify I thoroughly understood.
Nearly all vertibrates have the eye cofiguration of the supior oblique muscle passing from behind the eye, through a looped trochlea, and then connecting to the eye. The difference between different animals is the position of the trochlea relative to the eye and therefore the angle of the bend in the dorsal oblique muscle. As the challenge states in a human the trochlea is above and in front of the eye so the angle of the bend of the "sling" is quite acute.
In an opposum though the trochlea is behind and above the eyebal so the angle is pretty oblique (about 120 degrees). In this article (well, I can't post the url, sorry) you can view these structures for the rabbit, pig, monkey, and cat. The article's a little old but I'm not a biologist so I simply grabbed what I could google.
The thing to note is that the position of the trochlea corresponds very closely to the orientation of the frontal bone (forehead on humans) . This implies the trochlea position did not evolve from natural selection for efficient eyeball movement but instead efficient eyeball movement was and adative response to trochlea position which itself is a result of the evolution of the frontal bone.
(Adaptive response {is that the correct term; I'm not a biologist} is very common in evolution. Probably the best known example is the lungs which evolved as a bouyancy bladder in fish and only then adapted in function to process air. The wings of the bat are probably another adaptive response to what were probably webbing evolved toward catching bugs. In fact, I think adaptive response is the general rule of evolution but a real biologist can probably address that better than I can.)
Nearly all vertibrates have the eye cofiguration of the supior oblique muscle passing from behind the eye, through a looped trochlea, and then connecting to the eye. The difference between different animals is the position of the trochlea relative to the eye and therefore the angle of the bend in the dorsal oblique muscle. As the challenge states in a human the trochlea is above and in front of the eye so the angle of the bend of the "sling" is quite acute.
In an opposum though the trochlea is behind and above the eyebal so the angle is pretty oblique (about 120 degrees). In this article (well, I can't post the url, sorry) you can view these structures for the rabbit, pig, monkey, and cat. The article's a little old but I'm not a biologist so I simply grabbed what I could google.
The thing to note is that the position of the trochlea corresponds very closely to the orientation of the frontal bone (forehead on humans) . This implies the trochlea position did not evolve from natural selection for efficient eyeball movement but instead efficient eyeball movement was and adative response to trochlea position which itself is a result of the evolution of the frontal bone.
(Adaptive response {is that the correct term; I'm not a biologist} is very common in evolution. Probably the best known example is the lungs which evolved as a bouyancy bladder in fish and only then adapted in function to process air. The wings of the bat are probably another adaptive response to what were probably webbing evolved toward catching bugs. In fact, I think adaptive response is the general rule of evolution but a real biologist can probably address that better than I can.)
It appears to be the standard argument from incredulity and lack of knowledge therefore Goddidit.
Alate_One
Well-known member
And of course an incorrect assumption about how evolution works (big surprise given the tattoo comments). Bob assumes the trochlea evolved to perform a function with the same skull shape, rather than the skull shape changing around the trochlea and the orientation being a result of said change in skull shape. Which if he'd looked at the anatomy of other vertebrates, the answer would have been obvious.
In short its a rather poor attempt to come up with is own "irreducibly complex" structure. Bob didn't even do as well as Behe or the others (who also failed in producing an example of irreducible complexity).
GuySmiley
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Me too! :wave:
Where are the fossil records showing these skulls that were shaped different as it relates to the trochlea?
Any fossilized skull will do. All one would need to do is find a frontal bone where the superior oblique muscle does not appear to run from the back to the front where it have to bend down to the eye in through some form of trochlea (trochlei are cartilage so don't fossilize well, but their existence can probably be determined by the fossiled track of the superior oblique muscle). I do not know that any has actually done research into the evolution of the trochlea itself but so far as I know, no fossilized skull shows any other arrangement of the superior oblique muscle. Feel free to look through fossils you know about and let me know if you find any that imply otherwise.
Any fossilized skull will do. All one would need to do is find a frontal bone where the superior oblique muscle does not appear to run from the back to the front where it have to bend down to the eye in through some form of trochlea (trochlei are cartilage so don't fossilize well, but their existence can probably be determined by the fossiled track of the superior oblique muscle). I do not know that any has actually done research into the evolution of the trochlea itself but so far as I know, no fossilized skull shows any other arrangement of the superior oblique muscle. Feel free to look through fossils you know about and let me know if you find any that imply otherwise.
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