You are welcome to substitute "crocodile" for Alligator. My points still stand. Yours still fall.
Posted on 07/03/2006 12:32:51 PM PDT by Al Simmons
In the 1993 movie Jurassic Park, one human character tells another that a Tyrannosaurus rex can't see them if they don't move, even though the beast is right in front of them. Now, a scientist reports that T. rex had some of the best vision in animal history. This sensory prowess strengthens arguments for T. rex's role as predator instead of scavenger.
Scientists had some evidence from measurements of T. rex skulls that the animal could see well. Recently, Kent A. Stevens of the University of Oregon in Eugene went further.
He used facial models of seven types of dinosaurs to reconstruct their binocular range, the area viewed simultaneously by both eyes. The wider an animal's binocular range, the better its depth perception and capacity to distinguish objectseven those that are motionless or camouflaged.
T. rex had a binocular range of 55, which is wider than that of modern hawks, Stevens reports in the summer Journal of Vertebrate Paleontology. Moreover, over the millennia, T. rex evolved features that improved its vision: Its snout grew lower and narrower, cheek grooves cleared its sight lines, and its eyeballs enlarged. ...
Stevens also considered visual acuity and limiting far pointthe greatest distance at which objects remain distinct. For these vision tests, he took the known optics of reptiles and birds, ranging from the poor-sighted crocodile to the exceptional eagle, and adjusted them to see how they would perform inside an eye as large as that of T. rex. "With the size of its eyeballs, it couldn't help but have excellent vision," Stevens says.
He found that T. rex might have had visual acuity as much as 13 times that of people. By comparison, an eagle's acuity is 3.6 times that of a person.
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T. rex might also have had a limiting far point of 6 kilometers, compared with the human far point of 1.6 km. These are best-case estimates, Stevens says, but even toward the cautious end of the scale, T. rex still displays better vision than what's needed for scavenging.
The vision argument takes the scavenger-versus-predator debate in a new direction. The debate had focused on whether T. rex's legs and teeth made it better suited for either lifestyle.
Stevens notes that visual ranges in hunting birds and snapping turtles typically are 20 wider than those in grain-eating birds and herbivorous turtles.
In modern animals, predators have better binocular vision than scavengers do, agrees Thomas R. Holtz Jr. of the University of Maryland at College Park. Binocular vision "almost certainly was a predatory adaptation," he says.
But a scavenging T. rex could have inherited its vision from predatory ancestors, says Jack Horner, curator of paleontology at the Museum of the Rockies in Bozeman, Mont. "It isn't a characteristic that was likely to hinder the scavenging abilities of T. rex and therefore wasn't selected out of the population," Horner says.
Stevens says the unconvincing scene in Jurassic Park inspired him to examine T. rex's vision because, with its "very sophisticated visual apparatus," the dinosaur couldn't possibly miss people so close by. Sight aside, says Stevens, "if you're sweating in fear 1 inch from the nostrils of the T. rex, it would figure out you were there anyway."
Stevens, K.A. 2006. Binocular vision in theropod dinosaurs. Journal of Vertebrate Paleontology 26(June):321-330.
You have a citation for this? Evidence? Studies of mutation rates in alligators?
You are welcome to substitute "crocodile" for Alligator. My points still stand. Yours still fall.
You haven't demonstrated anything at all about mutation rates.
Pinging a few atheists.
"Label yourself, then. I'm disinterested"
I'm sure you are. I could be mistaken but saying alligators are perfectly suited to their enviroment and haven't changed, to me, would be closer to creationism than Darwinism.
BTW, I don't need to "label" myself to participate in a discussion. Maybe I should?
For all we know, they were cross-eyed. Don't horses have an unusual range of vision which is why they wear blinders?
"You haven't demonstrated anything at all about mutation rates."
That's because he doesn't know anything about them and is making it up as he goes along.
This nonsense about alligator mutation rates comes from the same school of biology that claims, after gazillions of radiation induced mutations, that fruit flies are still fruit flies.
"You have a citation for this? Evidence? Studies of mutation rates in alligators?" - js1138
Since when does posting sources *ever* pin down Darwinists?! You'll ignore it or deny it (occasionally mock it) and move on.
Nonetheless...
| Crocodiles first appeared nearly 160 million years ago and have changed very little ... www.skullsunlimited.com/crocodylia.htm - 36k - |
If I see one more thing about "alligator mutation rates" I'm gonna shoot myself. Don't worry about supplying the gun, I own several (smiling?)
Personal attacks aside (you offer little else, it seems), **random** mutations must involve mathematical probabilities...something that can either be shown/supported or discarded.
That's not made up.
What studies do you have of mutation rates for crocks and alligators?
On the contrary, speciation from external bias (e.g. iradiation) rather than from random happenstance is the antithesis of "nonsense." Such cause and effect is the entire subject of debate in this controversy.
So if you didn't make it up, where are your citations for studies of mutation rate in crocks and alligators?
Show us where you got the information regarding mutation rates in alligators.
No, what you said all along was/is untrue. You are confused by the difference between macro and micro derivation of a conclusion.
To wit: on the micro level it might be accurate to say that I don't have the specific mutation rates of alligators/crocodiles on the tip of my tongue...but at the macro level (e.g. the big picture) it is inaccurate to say the same thing...because species that are little-changed over 200 million years clearly have low mutation rates.
Which is to say, I know the macro rate of mutation. In contrast, you are desperately clinging to the fact that I don't know the specific micro level mutation rates as if that myopic viewpoint disproves the bigger picture.
It doesn't.
you found ROVER!!!
please send him back!
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